I started getting calls and visits yesterday from homeowners and growers with complaints about worm infestations. Fall armyworm is the culprit, and apparently the problem is severe and widespread.
Fall armyworms are spreading into newly planted fields of oats, rye and other fall grass forages, and into newly seeded home lawns. Calls are coming in mainly from Surry and Isle of Wight Counties, but that could be the result of the attention growers and crop advisers are paying to fields in those areas.
One common denominator seems to be that most infested fields are adjacent to pasture or hay fields. Apparently, the worms have been developing in those fields and are now on-the-move into fields with tender newly emerge leaf shoots.
Based on the number of reports, I suspect this problem is even more widespread. Emerging wheat and barley fields are certainly also at risk. Fall armyworm has two strains and I suspect this is the grass strain. I also suspect that this widespread infestation is the result of a huge migratory flight from the south, another in a long line of caterpillar invasions that started with early corn earworm problems back in July.
This late-season fall armyworm invasion is certainly an unusual problem.
I have never seen anything like this in the 22 years I have been working in this area. Rod Youngman on the main campus (he works with insect pests of turf and forages) advised that any of the pyrethroids labeled for forages or small grains should provide good control if applied at the high rate, but should be applied NOW.
He believes that seedlings are the most at risk and should be treated ASAP. Fall armyworms are surface plant feeders, so they are pretty vulnerable to pesticides. We also believe that fields grazed off by these worms should spring back once they have cycled out. Their life cycle should put them into to the pupal stage in another week or less. And of course, a good hard frost would take-em-out.
Wednesday, October 27, 2010
Tuesday, September 21, 2010
Virginia Peanuts: Spider Mite Infestations Picking Up
From Ames Herbert, Virginia Tech Extension Entomologist
It is not surprising that we are getting reports of spider mite build-ups in peanut fields. There are areas that have been fighting this dry weather pest for several weeks. These newer outbreaks are particularly bothersome as they are coming so close to the end of the season.
D. Rick Brandenburg (NCSU) and I have done a lot of work on how to achieve the best control of spider mites in peanuts. There are several limiting factors, not the least of which is the limited number of products registered for spider mite control in peanut. There are only three products currently labeled, Danitol, Brigade and Comite.
For reasons that must have to do with marketing, Comite has not been readily available to Virginia growers for the last 3 or 4 years. That leaves Danitol and Brigade (= Capture) which are both pyrethroids. These products if applied with high spray volume (15 + gpa) will provide good knockdown of adult and immature mites. But, neither kills the eggs so if applications are made to fields where there are a lot of eggs, these hatch in 2 or 3 days and the infestation begins again.
Our work showed that the only way to make these products work well was to make two sequential applications about 5 to 7 days apart. The first application knocks down the adults and immatures, and the second gets the new hatchlings, thus breaking the cycle.
But, this late in the season when digging will begin soon, we are recommending that if mites are doing a lot of damage and need to be controlled, make a single application using the highest labeled rate, knock them back, and hope for the best.
It is not surprising that we are getting reports of spider mite build-ups in peanut fields. There are areas that have been fighting this dry weather pest for several weeks. These newer outbreaks are particularly bothersome as they are coming so close to the end of the season.
D. Rick Brandenburg (NCSU) and I have done a lot of work on how to achieve the best control of spider mites in peanuts. There are several limiting factors, not the least of which is the limited number of products registered for spider mite control in peanut. There are only three products currently labeled, Danitol, Brigade and Comite.
For reasons that must have to do with marketing, Comite has not been readily available to Virginia growers for the last 3 or 4 years. That leaves Danitol and Brigade (= Capture) which are both pyrethroids. These products if applied with high spray volume (15 + gpa) will provide good knockdown of adult and immature mites. But, neither kills the eggs so if applications are made to fields where there are a lot of eggs, these hatch in 2 or 3 days and the infestation begins again.
Our work showed that the only way to make these products work well was to make two sequential applications about 5 to 7 days apart. The first application knocks down the adults and immatures, and the second gets the new hatchlings, thus breaking the cycle.
But, this late in the season when digging will begin soon, we are recommending that if mites are doing a lot of damage and need to be controlled, make a single application using the highest labeled rate, knock them back, and hope for the best.
Virginia Soybeans: Loopers Phasing Out, Finally
From Ames Herbert, Virginia Tech Extension Entomologist
Although there are still soybean loopers in a lot of fields, the numbers are declining. The larger worms are going into pupation and, thankfully, no new eggs are being deposited. For example, I visited several fields where last week the numbers were in the 15 to 20/15 sweep range and found only 2 or 3 larger worms remaining. Also, most of these fields were much closer to being mature enough to be in the "safe" zone. I am still getting a few calls and am referring them to last week's advisory note. One nice feature of our advisory is that it archives notes.
To see last week's note that provides guidelines for determining the need for late season looper treatment, go to www.sripmc.org/virginia and scroll down to the Sept. 9 soybean looper note.
Although there are still soybean loopers in a lot of fields, the numbers are declining. The larger worms are going into pupation and, thankfully, no new eggs are being deposited. For example, I visited several fields where last week the numbers were in the 15 to 20/15 sweep range and found only 2 or 3 larger worms remaining. Also, most of these fields were much closer to being mature enough to be in the "safe" zone. I am still getting a few calls and am referring them to last week's advisory note. One nice feature of our advisory is that it archives notes.
To see last week's note that provides guidelines for determining the need for late season looper treatment, go to www.sripmc.org/virginia and scroll down to the Sept. 9 soybean looper note.
Brown marmorated stink bug found on the Eastern Shore of Virginia
From Tom Kuhar, Virginia Tech Entomologist
The brown marmorated stink bug has now been found on the Eastern Shore of Virginia.
Nymphs of this exotic pest were feeding on yellow squash in our research plots in Painter, VA. As far as I know, this is the first documented occurrence of this pest on the Eastern Shore of Virginia.
Based on reports from New Jersey, West Virginia, Maryland, Delaware, Pennsylvania, and western counties of Virginia, this insect can be quite damaging to numerous crops, and population densities can build up to extreme levels.
Crops that can be particularly hard hit include tree fruit, peppers, tomatoes, sweet corn, and from what I saw, cucurbits as well. In the fall, this stink bug will also aggregate on and in building structures similar to the Asian multicolored lady beetle. Click more to view an image of this pest. [More]
The brown marmorated stink bug has now been found on the Eastern Shore of Virginia.
Nymphs of this exotic pest were feeding on yellow squash in our research plots in Painter, VA. As far as I know, this is the first documented occurrence of this pest on the Eastern Shore of Virginia.
Based on reports from New Jersey, West Virginia, Maryland, Delaware, Pennsylvania, and western counties of Virginia, this insect can be quite damaging to numerous crops, and population densities can build up to extreme levels.
Crops that can be particularly hard hit include tree fruit, peppers, tomatoes, sweet corn, and from what I saw, cucurbits as well. In the fall, this stink bug will also aggregate on and in building structures similar to the Asian multicolored lady beetle. Click more to view an image of this pest. [More]
Friday, September 17, 2010
Soybean Loopers Still Present But Numbers Declining
From Ames Herbert, Virginia Tech Extension Entomologist
Although there are still soybean loopers in a lot of fields, the numbers are declining.
The larger worms are going into pupation and, thankfully, no new eggs are being deposited. For example, I visited several fields where last week the numbers were in the 15 to 20/15 sweep range and found only 2 or 3 larger worms remaining. Also, most of these fields were much closer to being mature enough to be in the "safe" zone. I am still getting a few calls and am referring them to last week's advisory note.
One nice feature of our advisory is that it archives notes. To see last week's note that provides guidelines for determining the need for late season looper treatment, go to www.sripmc.org/virginia and scroll down to the Sept. 9 soybean looper note
Although there are still soybean loopers in a lot of fields, the numbers are declining.
The larger worms are going into pupation and, thankfully, no new eggs are being deposited. For example, I visited several fields where last week the numbers were in the 15 to 20/15 sweep range and found only 2 or 3 larger worms remaining. Also, most of these fields were much closer to being mature enough to be in the "safe" zone. I am still getting a few calls and am referring them to last week's advisory note.
One nice feature of our advisory is that it archives notes. To see last week's note that provides guidelines for determining the need for late season looper treatment, go to www.sripmc.org/virginia and scroll down to the Sept. 9 soybean looper note
Thursday, September 9, 2010
Soybean Loopers: When Can You Stop Spraying? Rules Of Thumb.
From Ames Herbert, Virginia Tech Extension Entomologist
Soybean looper calls are pouring in from all over the eastern half of the state. It is adding insult to injury, having to treat fields for the second, third, or even a fourth time in the most extreme cases. On top of that, many fields are so drought stressed they are struggling to stay alive.
When helping growers make the decision on whether to treat a field for loopers we have to take the time to consider several components that influence the decision: the maturity of the crop, the health of the leaf canopy, and the number of loopers present.
Let's take them one at the time.
How susceptible? In terms of crop susceptibility, after some long discussions with soybean agronomists (David Holshouser at VT and Jim Dumphy at NCSU), we came up with a rule-of-thumb as to when fields are safe, that is, worms can be left untreated with no fear of lost yields.
We suggest that fields will need to be protected as long as the pods are still green and until the lower leaves are just beginning to yellow. This should correspond, more or less, with the R6.5 stage (10 days after R6.0 = full green seed). If leaves are beginning to yellow up the stem, not from drought but from the maturity process, and there are any pods on the plant that are beginning to yellow, the field is safe, no need to treat.
How much canopy have you got? Next we have to determine the health of the leaf canopy -- robust, average, or thin. Each can tolerate different amounts of leaf loss before reducing yield potential.
How much defoliation have you sustained? In this canopy assessment, we need to take a stab at estimating the current percent defoliation. This is not an exact measure, but your best estimate looking over the entire canopy top to bottom. The eyes tend to focus on those badly defoliated top leaves. Look beyond those and try to come up with an overall average.
One thing we (and others) have noticed about soybean loopers is that their feeding is often in mid-canopy, not at the top like most other defoliators. All the more reason to inspect the entire canopy.
How many loopers are present? There is not a single threshold because of all the factors we have just discussed, but a very general rule of thumb is that 15-20 or greater/15 sweeps constitutes a potential threat, depending on the maturity and canopy health.
Thresholds vary quite a bit from state to state but this one falls pretty well in line with the other states.
In considering these components, some fields will be no-brainers. Mature fields (late R6 or older) or fields with robust canopies and just a few loopers (10 or less/15 sweeps) can be left alone.
On the other end of the spectrum, early R6 stage or younger fields with stressed, thin canopies and 15-20 or more loopers/15 sweeps need to be treated. This week in Virginia, there are a lot of fields in the grey zone (plants are in the mid to late R5 to early R6 stage, the canopy is average, the looper number is in the 12-18 range, and defoliation is less than 20%).
I tell folks, if they can do this:
It all sounds pretty complicated and it is, but taking the time to consider these components should help determine if a field needs to be treated. Some will and some won't, and allow growers to protect at-risk fields but save money on safe fields.
When will this looper flight end and what will stop it? I have been asked. I wish I knew. We need rain, badly, which will move fields to maturity and get us out of this mess.
Soybean looper calls are pouring in from all over the eastern half of the state. It is adding insult to injury, having to treat fields for the second, third, or even a fourth time in the most extreme cases. On top of that, many fields are so drought stressed they are struggling to stay alive.
When helping growers make the decision on whether to treat a field for loopers we have to take the time to consider several components that influence the decision: the maturity of the crop, the health of the leaf canopy, and the number of loopers present.
Let's take them one at the time.
How susceptible? In terms of crop susceptibility, after some long discussions with soybean agronomists (David Holshouser at VT and Jim Dumphy at NCSU), we came up with a rule-of-thumb as to when fields are safe, that is, worms can be left untreated with no fear of lost yields.
We suggest that fields will need to be protected as long as the pods are still green and until the lower leaves are just beginning to yellow. This should correspond, more or less, with the R6.5 stage (10 days after R6.0 = full green seed). If leaves are beginning to yellow up the stem, not from drought but from the maturity process, and there are any pods on the plant that are beginning to yellow, the field is safe, no need to treat.
How much canopy have you got? Next we have to determine the health of the leaf canopy -- robust, average, or thin. Each can tolerate different amounts of leaf loss before reducing yield potential.
- Robust fields (mid chest or higher) can tolerate a lot of feeding.
- Average fields (upper thigh to mid chest) can tolerate normal amounts of feeding.
- Thin canopy fields (mid thigh or below) cannot tolerate additional leaf loss.
How much defoliation have you sustained? In this canopy assessment, we need to take a stab at estimating the current percent defoliation. This is not an exact measure, but your best estimate looking over the entire canopy top to bottom. The eyes tend to focus on those badly defoliated top leaves. Look beyond those and try to come up with an overall average.
One thing we (and others) have noticed about soybean loopers is that their feeding is often in mid-canopy, not at the top like most other defoliators. All the more reason to inspect the entire canopy.
How many loopers are present? There is not a single threshold because of all the factors we have just discussed, but a very general rule of thumb is that 15-20 or greater/15 sweeps constitutes a potential threat, depending on the maturity and canopy health.
Thresholds vary quite a bit from state to state but this one falls pretty well in line with the other states.
In considering these components, some fields will be no-brainers. Mature fields (late R6 or older) or fields with robust canopies and just a few loopers (10 or less/15 sweeps) can be left alone.
On the other end of the spectrum, early R6 stage or younger fields with stressed, thin canopies and 15-20 or more loopers/15 sweeps need to be treated. This week in Virginia, there are a lot of fields in the grey zone (plants are in the mid to late R5 to early R6 stage, the canopy is average, the looper number is in the 12-18 range, and defoliation is less than 20%).
I tell folks, if they can do this:
- Take a close look at these fields and make a mental image of the extent of defoliation.
- Revisit in 2-3 days (no longer) to see if it has greatly increased.
- If the percent defoliation has increased and loopers are still present at or near the threshold, treat it.
- If the level of defoliation has not increased much and/or the looper numbers have decreased, don't treat.
It all sounds pretty complicated and it is, but taking the time to consider these components should help determine if a field needs to be treated. Some will and some won't, and allow growers to protect at-risk fields but save money on safe fields.
When will this looper flight end and what will stop it? I have been asked. I wish I knew. We need rain, badly, which will move fields to maturity and get us out of this mess.
Thursday, September 2, 2010
Soybean Loopers Turning Up In Higher-Than-Normal Numbers And On A Wide Basis
From Ames Herbert, Virginia Tech Extension Entomologist
Soybean loopers are now being reported in soybean fields across much of the eastern side of the state. In past years they were mostly confined to southeastern counties. This infestation has broken all the records in terms of intensity (as many as 100+/15 sweeps in some fields) and geography (now being reported from Middle Peninsula and Northern Neck counties).
This must be due to the persistent hot, dry weather, and the high percentage of fields previously treated with insecticides. Loopers are easy to identify but there is some confusion about their color. Soybean loopers have both a "green" and a "black" color phase (see images in this PowerPoint file).
We are seeing both color phases in our samples. There may be some cabbage loopers (a completely different species) mixed in, but we have not verified this. There are no exact thresholds for loopers in soybean, so treatment should be based on the amount of leaf feeding in relation to the size of the total canopy.
But, a very loose rule of thumb could be that 20 or more per 15 sweep net sweeps may constitute a threat.
Fewer than that, especially in tall, full canopy fields probably does not constitute a threat. Some fields are getting close to maturity with pods and leaves beginning to yellow. Loopers are not a threat to those fields.
Pyrethroids should not be figured into a looper treatment decision. They are less than effective. If stink bugs are present in looper infested fields, I would consider adding Orthene to the looper insecticide.
Orthene will provide good control of both green and brown stink bugs where the pyrethroid would miss some of the browns. Oddly, we are seeing more brown stink bugs in some fields than greens, which is opposite of what we are used to seeing.
We have initiated 5 different field trials to evaluate the effectiveness of many different insecticides/rates for loopers. Results will be presented at our annual Pre-Harvest Field Tour scheduled for Sept. 14.
Soybean loopers are now being reported in soybean fields across much of the eastern side of the state. In past years they were mostly confined to southeastern counties. This infestation has broken all the records in terms of intensity (as many as 100+/15 sweeps in some fields) and geography (now being reported from Middle Peninsula and Northern Neck counties).
This must be due to the persistent hot, dry weather, and the high percentage of fields previously treated with insecticides. Loopers are easy to identify but there is some confusion about their color. Soybean loopers have both a "green" and a "black" color phase (see images in this PowerPoint file).
We are seeing both color phases in our samples. There may be some cabbage loopers (a completely different species) mixed in, but we have not verified this. There are no exact thresholds for loopers in soybean, so treatment should be based on the amount of leaf feeding in relation to the size of the total canopy.
But, a very loose rule of thumb could be that 20 or more per 15 sweep net sweeps may constitute a threat.
Fewer than that, especially in tall, full canopy fields probably does not constitute a threat. Some fields are getting close to maturity with pods and leaves beginning to yellow. Loopers are not a threat to those fields.
Pyrethroids should not be figured into a looper treatment decision. They are less than effective. If stink bugs are present in looper infested fields, I would consider adding Orthene to the looper insecticide.
Orthene will provide good control of both green and brown stink bugs where the pyrethroid would miss some of the browns. Oddly, we are seeing more brown stink bugs in some fields than greens, which is opposite of what we are used to seeing.
We have initiated 5 different field trials to evaluate the effectiveness of many different insecticides/rates for loopers. Results will be presented at our annual Pre-Harvest Field Tour scheduled for Sept. 14.
Soybean Aphids Hit Treatment Level In One Hot Spot
From Ames Herbert, Virginia Tech Extension Entomologist
A couple of new things to report from our statewide soybean survey:
A couple of new things to report from our statewide soybean survey:
- Soybean aphid has greatly exceeded the threshold (250 aphids/plant) in at least two fields in Gloucester County. Our scout has been watching this area closely for several weeks as it has been the "hot spot" in the state. As of this week, the population has jumped. As the beans are still in the R4-R5 growth stage, we are recommending a pyrethroid treatment. Pyrethroids are effective in controlling this aphid species.
- The scout also brought in samples of brown marmorated stink bug (BMSB) nymphs collected from soybean fields in three counties, Culpeper, Augusta and Clark. These are in the upper- central and northern Virginia. The counts were low in these fields, only about 1/15 sweeps, which is not alarming, but definitely warrants watching. Reports of huge masses of BMSB are starting to come in from places like Fairfax, Virginia, with bugs massing on trees, especially maples, and vegetables of all kinds.
Plenty Of Corn Earworm Moths, But Will That Mean More Worms?
From Ames Herbert, Virginia Tech Extension Entomologist
Earworm moths are still flying.
Trap catches are high in many areas, and windshields are spattered.
One fellow commented that the other night coming home from a meeting, he had to stop twice to clean the moth gunk off his windshield. One observation, and I hope this holds, is that in the past this late season moth flight did not result in new worm infestations.
A lot of insect behavior is relegated by environmental cues. Days are definitely getting shorter. Is this reduced photoperiod (shorter day length) causing moths not to lay as many eggs?
Not sure, but for whatever reason, in my experience it has been rare to see worm infestations initiate in September.
We are hearing of many fields with a few earworms, maybe left over from the earlier flight, but none with the huge numbers we had a few weeks ago. Let's hope we are finally seeing the end of this pest, for this season at least.
Earworm moths are still flying.
Trap catches are high in many areas, and windshields are spattered.
One fellow commented that the other night coming home from a meeting, he had to stop twice to clean the moth gunk off his windshield. One observation, and I hope this holds, is that in the past this late season moth flight did not result in new worm infestations.
A lot of insect behavior is relegated by environmental cues. Days are definitely getting shorter. Is this reduced photoperiod (shorter day length) causing moths not to lay as many eggs?
Not sure, but for whatever reason, in my experience it has been rare to see worm infestations initiate in September.
We are hearing of many fields with a few earworms, maybe left over from the earlier flight, but none with the huge numbers we had a few weeks ago. Let's hope we are finally seeing the end of this pest, for this season at least.
Risk Low For Soybean Rust In Virginia This Season If Hot Weather Continues
The following update was provided by Drs. Pat Phipps and Darcy Telenko at the Virginia Tech Tidewater Ag Research and Extension Center at Suffolk
Most full season (May planted) soybeans (group IV and V) are at or approaching R6 (full seed). Group III soybean are beginning to yellow and drop leaves. Therefore, most of our full-season crop should suffer no yield loss from soybean rust.
Double-crop soybean are just entering R5 (beginning seed); therefore, this crop will need to be protected for approximately 2 more weeks. In drought-stricken areas, recent rainfall has allowed addition flowering and pod set at the top of the plant.
In the most severely drought-stressed areas of Virginia, soybean are one to two stages behind. Such fields will need protection for another 2 weeks.
Observation and Outlook:- Disease samples of leaflets from sentinel plots at the Tidewater AREC in Suffolk have been examined this week, and no soybean rust (SBR) was found. The risk of SBR reaching Virginia is likely to remain low as long as high temperatures continue to reach into the 90's.
Most full season (May planted) soybeans (group IV and V) are at or approaching R6 (full seed). Group III soybean are beginning to yellow and drop leaves. Therefore, most of our full-season crop should suffer no yield loss from soybean rust.
Double-crop soybean are just entering R5 (beginning seed); therefore, this crop will need to be protected for approximately 2 more weeks. In drought-stricken areas, recent rainfall has allowed addition flowering and pod set at the top of the plant.
In the most severely drought-stressed areas of Virginia, soybean are one to two stages behind. Such fields will need protection for another 2 weeks.
Observation and Outlook:- Disease samples of leaflets from sentinel plots at the Tidewater AREC in Suffolk have been examined this week, and no soybean rust (SBR) was found. The risk of SBR reaching Virginia is likely to remain low as long as high temperatures continue to reach into the 90's.
Friday, August 27, 2010
Tidewater Late-Season Field Crops Tour And Dinner - September 14
The 2010 Tidewater Late-Season Field Crops tour and dinner is scheduled on Tuesday, September 14 at the Virginia Tech Tidewater Agricultural Research and Extension Center at 1045 Hare Road in Suffolk, Virginia.
Tour stops include: cotton defoliation and rotation; barley-wheat-soybean systems, peanut and sorghum variety trials, peanut disease control innovations and insect management in cotton and soybeans. CCA CEU & Private Pesticide recertification credits will be available.
Registration begins at 1:30 p.m. and tours start at 2:00 pm. Pre-registration is required for the tour/dinner. Please contact Gail White at 757-657-6450, ext. 430 or e-mail guwhite@vt.edu by September 6th.
If you are a person with a disability and desire any assistive devices, services or other accommodations to participate in this activity, please contact the Tidewater Agricultural Research and Extension Center at 757-657-6450 (TDD number is 800-828-1120) during business hours of 8 a.m. and 4:30 p.m. to discuss accommodations five days prior to the event.
Tour stops include: cotton defoliation and rotation; barley-wheat-soybean systems, peanut and sorghum variety trials, peanut disease control innovations and insect management in cotton and soybeans. CCA CEU & Private Pesticide recertification credits will be available.
Registration begins at 1:30 p.m. and tours start at 2:00 pm. Pre-registration is required for the tour/dinner. Please contact Gail White at 757-657-6450, ext. 430 or e-mail guwhite@vt.edu by September 6th.
If you are a person with a disability and desire any assistive devices, services or other accommodations to participate in this activity, please contact the Tidewater Agricultural Research and Extension Center at 757-657-6450 (TDD number is 800-828-1120) during business hours of 8 a.m. and 4:30 p.m. to discuss accommodations five days prior to the event.
Thursday, August 26, 2010
Corn Earworms Building Again In Soybeans, Loopers Becoming More Apparent
From Ames Herbert, Virginia Tech Extension Entomologist
Although the corn earworm flight is still strong, we are not hearing of many fields with high numbers of worms. However, we are hearing of a lot of fields with pod-stage thresholds and many are being re-sprayed.
Several folks have reported seeing newly hatched small worms but are waiting a few days before spraying to see how things develop. Holding off a few more days may mean the difference in having to treat a third time.
There are a lot of fields that seem to be holding with no new earworms developing, especially the early planted fields. More infestations are being reported in later-planted double crop fields.
This is a typical pattern as the pods in early planted fields are getting to the point where they are no longer attractive or vulnerable. Maybe this second infestation will not be as bad as we expected, but we have another week or two before we will know.
Our advice is to keep checking fields at least every 5 days or so, until fields reach the R7 growth stage. As a side note, our pyrethroid testing of adult corn earworms is showing a gradual increase in the level of survivorship, now averaging over 40% for this past week (see chart below).
Better consider one of the non-pyrethroid options.
We are finding (and hearing about) more soybean loopers. The most we have encountered is about 15 to 20 per 15 sweeps, but even at those numbers, the level of defoliation is not bad or to the point where fields need protection. This may get worse, or may not, depending on a lot of factors.
One of the oddest situations is the extremely large numbers of green cloverworms that are being reported in some areas. Folks are finding 30-40 and more per 15 sweeps and they are definitely working on the foliage.
We always see cloverworms in soybean fields but never at these high levels. They are having to be controlled in fields with limited growth (due to slow growth during the hot dry weather).
Reports from Maryland are saying that brown marmorated stink bugs are inundating soybean fields in western and central Maryland. We have known about this pest for several years. It is a native of China, was first reported in Virginia in 2005 (one specimen) and has gradually increased in number. It has become established in Virginia and is now causing problems in vegetable a fruit crops.
Soybean is one of its many host crops in China and as we feared, it is now moving into that crop. We have found a few in Virginia soybean fields, about 1 per 15 sweeps in a couple of fields. We do not know much about damage potential or control options but a lot of research is underway.
Although the corn earworm flight is still strong, we are not hearing of many fields with high numbers of worms. However, we are hearing of a lot of fields with pod-stage thresholds and many are being re-sprayed.
Several folks have reported seeing newly hatched small worms but are waiting a few days before spraying to see how things develop. Holding off a few more days may mean the difference in having to treat a third time.
There are a lot of fields that seem to be holding with no new earworms developing, especially the early planted fields. More infestations are being reported in later-planted double crop fields.
This is a typical pattern as the pods in early planted fields are getting to the point where they are no longer attractive or vulnerable. Maybe this second infestation will not be as bad as we expected, but we have another week or two before we will know.
Our advice is to keep checking fields at least every 5 days or so, until fields reach the R7 growth stage. As a side note, our pyrethroid testing of adult corn earworms is showing a gradual increase in the level of survivorship, now averaging over 40% for this past week (see chart below).
Better consider one of the non-pyrethroid options.
We are finding (and hearing about) more soybean loopers. The most we have encountered is about 15 to 20 per 15 sweeps, but even at those numbers, the level of defoliation is not bad or to the point where fields need protection. This may get worse, or may not, depending on a lot of factors.
One of the oddest situations is the extremely large numbers of green cloverworms that are being reported in some areas. Folks are finding 30-40 and more per 15 sweeps and they are definitely working on the foliage.
We always see cloverworms in soybean fields but never at these high levels. They are having to be controlled in fields with limited growth (due to slow growth during the hot dry weather).
Reports from Maryland are saying that brown marmorated stink bugs are inundating soybean fields in western and central Maryland. We have known about this pest for several years. It is a native of China, was first reported in Virginia in 2005 (one specimen) and has gradually increased in number. It has become established in Virginia and is now causing problems in vegetable a fruit crops.
Soybean is one of its many host crops in China and as we feared, it is now moving into that crop. We have found a few in Virginia soybean fields, about 1 per 15 sweeps in a couple of fields. We do not know much about damage potential or control options but a lot of research is underway.
Monday, August 23, 2010
Large Corn Earworm Flight In Progress - Soybeans And Peanuts At Risk
From Ames Herbert, Virginia Tech Extension Entomologist
A very large movement of corn earworm moths is taking place throughout much of eastern Virginia. I did some driving throughout several counties this past Sunday nigh,t and there were so many moths flying it felt like being in a snow flurry.
Soybean and peanut fields are at very high risk to re-infestation of worms. Most fields were treated 2 weeks or more ago and are very susceptible to re-infestation.
Calls have already started coming in with growers and crop advisors seeing this re-infestation.
Here are several observations and recommendations.
A very large movement of corn earworm moths is taking place throughout much of eastern Virginia. I did some driving throughout several counties this past Sunday nigh,t and there were so many moths flying it felt like being in a snow flurry.
Soybean and peanut fields are at very high risk to re-infestation of worms. Most fields were treated 2 weeks or more ago and are very susceptible to re-infestation.
Calls have already started coming in with growers and crop advisors seeing this re-infestation.
Here are several observations and recommendations.
- First, I think this fight is comprised mostly of corn earworm (less possibility of tobacco budworm), and I think they are coming out of our own peanut and soybean fields. Because of this, they may represent survivors from previous sprays, so there could be even higher percentages with some level of pyrethroid resistance.
- My advice is to try to hold off on making applications for at least a 2 or 3 more days. By waiting, the moths will lay more eggs and more small larvae will hatch.
- Going too early in this flight cycle may mean yet another treatment. Of course, waiting too long will allow worms to begin feeding on pods.
- Worm must be 3/8 inch long or longer before they can feed on pods, and remember, we base our thresholds on these sizes-not the tiny worms.
- When you pull the trigger, go with idea that the best kill will be achieved having a non-pyrethroid in the mix. We have gone over those options several times. The newest option added to that list is Belt by Bayer CropScience. Belt is performing very well in our field trials at 3 oz/acre. The label goes from 2-3 oz. The 2 oz rate may be enough but we have not tested it. Belt is also showing some indication that it is providing good residual activity.
- Consero is also new and could present another good tank mix option. Consero is a co-pack of spinosad and gamma-cyhalothrin and is labeled at 2-3 oz/acre. Other non-pyrethroid standards are Larvin, Steward, Tracer and Orthene (which should only be used if tank-mixed with a pyrethroid).
Thursday, August 19, 2010
Soybeans: Second Big Moth Flight Plus Pyrethroid Resistance - A Perfect Storm
From Ames Herbert, Virginia Tech Extension Entomologist
As predicted, we are in the midst of a second flurry of corn earworm and tobacco budworm moth activity. Some black light traps are catching even higher numbers than during the first flight. Moths are flushing from peanut, cotton and soybean fields.
Each crop is presenting a different scenario in terms of risk to infestation and potential crop damage. I can almost guarantee that peanut and soybean fields will be re-infested with worms, and there is a very good possibility that the infestation will be a mix of both species.
As predicted, we are in the midst of a second flurry of corn earworm and tobacco budworm moth activity. Some black light traps are catching even higher numbers than during the first flight. Moths are flushing from peanut, cotton and soybean fields.
Each crop is presenting a different scenario in terms of risk to infestation and potential crop damage. I can almost guarantee that peanut and soybean fields will be re-infested with worms, and there is a very good possibility that the infestation will be a mix of both species.
- PEANUTS almost never suffer economically from worm feeding, but growers will likely not tolerate the worms and tank mix some insecticide with a planned fungicide application.
- SOYBEANS are a different story. This next influx of worms will coincide with pod development and fill. Many fields that have been drought stressed are getting some rain and plants are reflowering which makes them highly attractive to moths. I think pod thresholds will be met or exceeded in many fields and many will need to be re-sprayed.
Most of these fields have already been treated, but in my opinion, and in the opinion of other soybean entomologists, no product offers more than about 7 days residual activity so any field treated more than 7 days ago will be completely vulnerable to worms. Another piece of the puzzle is the continued high pyrethroid resistance levels of corn earworm. As of this week, we have tested 1,903 moths and survivorship has climbed back to over 40% (see the attached figure).
One sample this week reached 56%.
Is this resistance level increasing because many of these moths are from the worms that "escaped" the earlier pyrethroid sprays? Seems logical.
The best control will need to incorporate a non-pyrethroid (Larvin, Lannate, Steward, Tracer, Belt). Another tank mix that seems to be working well where ever it is being used (the Delta states, Tennessee, North Carolina) is to add 6 oz of Orthene to a full pyrethroid rate.
- COTTON may be the least attractive and least susceptible to this next influx of worms. The hot, dry weather has pushed cotton to cutout with many bolls already too tough to be damaged by worms. Much of the crop will be ready for defoliation within the next 3 weeks or so.
Without some top growth of new tender flowers, squares or small bolls, young worms will not be able to establish. And even if this top growth does become infested, it represents a very small proportion of the total yield, which makes controlling worms (the cost) a tough decision. [More]
Wednesday, August 18, 2010
Know The Difference Between Clover Worms And Soybean Loopers - Especially This Year
From Ames Herbert, Virginia Tech Extension Entomologist
Soybean looper is a common pest of our soybean crop and can be found in small numbers in most fields, most years. But it is very uncommon to have large infestations. The moths have to migrate into Virginia from the south, so when we do have big problems, they occur late in the season.
Our last bad soybean looper year was 2005. In 2005, they moved into several soybean fields in mid-September. Being unfamiliar with the pest, growers were not looking for them and not sampling fields.
In a few cases, fields were totally destroyed with loopers eating all the leaves leaving only leaf veins, stems and stalks (see the attached images, insecticide protected vs. unprotected soybean field).
This insect is capable of doing a lot of feeding in a short period of time. This is why I try to correct folks when they call green cloverworms--loopers.
Although green cloverworms do "loop" or "inch" when they crawl, they are distinctly different from soybean loopers both in appearance and in the rate they feed. Both are light green with white longitudinal strips down the tops of their backs and sides.
The differences are that green cloverworms are of equal girth from head to tail, have 3 pairs of abdominal prolegs, and wiggle vigorously if you put one in the palm of your hand (see the images below).
Loopers tend to be smaller at the head end and fatter towards the tail end, have only 2 pairs of abdominal prolegs, and they don't thrash around in your hand. And most importantly, loppers eat much more, worm-for-worm, compared with cloverworms.
A pattern that played out in 2005 was that all the fields hit hardest by soybean looper had been previously treated with a pyrethroid. The pyrethroids had reduced the beneficial population so when the invading moths laid their eggs, most survived. Large numbers of soybean looper moths have now been spotted in several fields in North Carolina.
Almost all of our soybean fields have been treated with a pyrethroid. We could be set up for a huge problem. Loopers are also fairly hard to control with pyrethroids which provide only about 50% control, at best. Products with pyrethroid/neonicotinoid mixes will not help.
Field trials in 2005 showed that only Lannate, Larvin, Steward and Tracer provided acceptable levels of control. Belt and Intrepid could likely be added to that list, but we have not evaluated those.
Bottom line, stay alert to these late season pests and keep a watch on your soybeans, especially any that have been treated with a pyrethroid.
Soybean looper is a common pest of our soybean crop and can be found in small numbers in most fields, most years. But it is very uncommon to have large infestations. The moths have to migrate into Virginia from the south, so when we do have big problems, they occur late in the season.
Our last bad soybean looper year was 2005. In 2005, they moved into several soybean fields in mid-September. Being unfamiliar with the pest, growers were not looking for them and not sampling fields.
In a few cases, fields were totally destroyed with loopers eating all the leaves leaving only leaf veins, stems and stalks (see the attached images, insecticide protected vs. unprotected soybean field).
This insect is capable of doing a lot of feeding in a short period of time. This is why I try to correct folks when they call green cloverworms--loopers.
Although green cloverworms do "loop" or "inch" when they crawl, they are distinctly different from soybean loopers both in appearance and in the rate they feed. Both are light green with white longitudinal strips down the tops of their backs and sides.
The differences are that green cloverworms are of equal girth from head to tail, have 3 pairs of abdominal prolegs, and wiggle vigorously if you put one in the palm of your hand (see the images below).
Loopers tend to be smaller at the head end and fatter towards the tail end, have only 2 pairs of abdominal prolegs, and they don't thrash around in your hand. And most importantly, loppers eat much more, worm-for-worm, compared with cloverworms.
A pattern that played out in 2005 was that all the fields hit hardest by soybean looper had been previously treated with a pyrethroid. The pyrethroids had reduced the beneficial population so when the invading moths laid their eggs, most survived. Large numbers of soybean looper moths have now been spotted in several fields in North Carolina.
Almost all of our soybean fields have been treated with a pyrethroid. We could be set up for a huge problem. Loopers are also fairly hard to control with pyrethroids which provide only about 50% control, at best. Products with pyrethroid/neonicotinoid mixes will not help.
Field trials in 2005 showed that only Lannate, Larvin, Steward and Tracer provided acceptable levels of control. Belt and Intrepid could likely be added to that list, but we have not evaluated those.
Bottom line, stay alert to these late season pests and keep a watch on your soybeans, especially any that have been treated with a pyrethroid.
Report: Statewide Soybean Aphid And Brown Marmorated Stink Bub Survey
With financial support from the Virginia Soybean Board and federal funding for our state IPM program, our soybean scout Ed Seymore has begun to monitor about 30 soybean fields for soybean aphid and a new invasive pest species, the brown marmorated stink bug.
From Aug. 2 to mid-August 2010, surveyed fields in the following counties had little to no soybean aphids: Augusta (0), Albemarle (0), Buckingham (0), Caroline (0), Charles City (0), Clark (0), Culpeper/Fauquier (1-5 aphids/plant), Gloucester (0), Goochland (0), Henrico (0), King and Queen (0), King William (0), Lancaster (0), Mathews (0), Middlesex (0), Orange (6-39 aphids/plant), Rockingham (0), and Shenandoah (0).
The economic threshold for soybean aphid is 250 aphids/plant so these low numbers of aphids do not pose any threat at present.
Very low numbers (about 1 per 15 sweeps) of brown marmorated stink bugs were detected in two soybean fields in central Culpeper County.
Researchers are still trying to determine the extent and nature of brown marmorated stink bug feeding injury to soybean, but it will likely pose a risk if populations become established.
-- From Ames Herbert, Virginia Tech Extension Entomologist
From Aug. 2 to mid-August 2010, surveyed fields in the following counties had little to no soybean aphids: Augusta (0), Albemarle (0), Buckingham (0), Caroline (0), Charles City (0), Clark (0), Culpeper/Fauquier (1-5 aphids/plant), Gloucester (0), Goochland (0), Henrico (0), King and Queen (0), King William (0), Lancaster (0), Mathews (0), Middlesex (0), Orange (6-39 aphids/plant), Rockingham (0), and Shenandoah (0).
The economic threshold for soybean aphid is 250 aphids/plant so these low numbers of aphids do not pose any threat at present.
Very low numbers (about 1 per 15 sweeps) of brown marmorated stink bugs were detected in two soybean fields in central Culpeper County.
Researchers are still trying to determine the extent and nature of brown marmorated stink bug feeding injury to soybean, but it will likely pose a risk if populations become established.
-- From Ames Herbert, Virginia Tech Extension Entomologist
Bayer Agrees To Phase Out Temik (Aldicarb) Production By End of 2014
The U.S. Environmental Protection Agency and Bayer CropScience, the manufacturer of Temik, have reached an agreement to end use of the Temik (chemically known as aldicarb) in the United States.
A new risk assessment conducted by EPA based on recently submitted toxicity data indicates that aldicarb, an N-methyl carbamate insecticide, no longer meets the agency s rigorous food safety standards and may pose unacceptable dietary risks, especially to infants and young children.
To address the most significant risks, Bayer has agreed first to end aldicarb use on citrus and potatoes and will adopt risk mitigation measures for other uses to protect groundwater resources. New measures to protect shallow drinking water wells in vulnerable areas of the southeastern U.S. coastal plain and lower application rates will be immediately added to product labels for use on cotton, soybeans, and peanuts.
The company will voluntarily phase out production of aldicarb by December 31, 2014. All remaining aldicarb uses will end no later than August 2018. Additionally, EPA plans to revoke the tolerances (legal pesticide residues allowed in food) associated with these commodities. EPA did this to ensure we have the safest food supply possible.
Based upon current toxicological studies, aldicarb at levels higher than those typically found in food has the potential to cause various effects such as sweating, nausea, dizziness and blurred vision, abdominal pain, vomiting, and diarrhea.
Aldicarb is registered for use as a systemic insecticide and nematicide on agricultural crops, and is formulated and marketed solely as a granular pesticide under the trade name Temik. During the phase-out, the pesticide will continue to be registered for use on cotton, dry beans, peanuts, soybeans, sugar beets, and sweet potatoes. Aldicarb products are not intended for sale to homeowners or for use in residential settings.
A restricted use pesticide, aldicarb may be applied only by trained, certified pesticide applicators. The memorandum of agreement and the agency s updated dietary risk assessment and supporting materials will be available in the aldicarb reregistration docket, EPA-HQ-OPP-2005-0163, and in the aldicarb Special Review docket, EPA-HQ-OPP-2006-0197, at regulations.gov. The U.S. has a safe and abundant food supply, and children and others should continue to eat a variety of foods, as recommended by the federal government and nutritional experts.
Click here for more information.
-- From Tom Kuhar, Virginia Tech Entomologist
A new risk assessment conducted by EPA based on recently submitted toxicity data indicates that aldicarb, an N-methyl carbamate insecticide, no longer meets the agency s rigorous food safety standards and may pose unacceptable dietary risks, especially to infants and young children.
To address the most significant risks, Bayer has agreed first to end aldicarb use on citrus and potatoes and will adopt risk mitigation measures for other uses to protect groundwater resources. New measures to protect shallow drinking water wells in vulnerable areas of the southeastern U.S. coastal plain and lower application rates will be immediately added to product labels for use on cotton, soybeans, and peanuts.
The company will voluntarily phase out production of aldicarb by December 31, 2014. All remaining aldicarb uses will end no later than August 2018. Additionally, EPA plans to revoke the tolerances (legal pesticide residues allowed in food) associated with these commodities. EPA did this to ensure we have the safest food supply possible.
Based upon current toxicological studies, aldicarb at levels higher than those typically found in food has the potential to cause various effects such as sweating, nausea, dizziness and blurred vision, abdominal pain, vomiting, and diarrhea.
Aldicarb is registered for use as a systemic insecticide and nematicide on agricultural crops, and is formulated and marketed solely as a granular pesticide under the trade name Temik. During the phase-out, the pesticide will continue to be registered for use on cotton, dry beans, peanuts, soybeans, sugar beets, and sweet potatoes. Aldicarb products are not intended for sale to homeowners or for use in residential settings.
A restricted use pesticide, aldicarb may be applied only by trained, certified pesticide applicators. The memorandum of agreement and the agency s updated dietary risk assessment and supporting materials will be available in the aldicarb reregistration docket, EPA-HQ-OPP-2005-0163, and in the aldicarb Special Review docket, EPA-HQ-OPP-2006-0197, at regulations.gov. The U.S. has a safe and abundant food supply, and children and others should continue to eat a variety of foods, as recommended by the federal government and nutritional experts.
Click here for more information.
-- From Tom Kuhar, Virginia Tech Entomologist
Friday, August 13, 2010
Corn Earworm Pressure In Flowering Soybeans - When Do You Treat?
To date, this has been one for the records in terms of corn earworm pressure in soybeans. Many of our fields have been treated, although most are still in the flowering/late flowering stage.
We do not have thresholds for flowering beans but know that high numbers of worms can do too much damage by eating all the flowers which can result in delayed maturity.
What's next for these fields? Will earworms recycle to present another threat to podding fields?
My guess is, yes, at least some percentage of fields may need to be retreated. The decision to retreat should be made based not on rumor, seeing spray rigs running in the neighbor s field, or conversations at the diner, but based on knowledge that thresholds have been met.
Growers cannot afford to make unnecessary sprays, especially with low yield potential and having already paid for one application. And, if a pyrethroid was used the first time we would strongly recommend that these second applications be non-pyrethroids.
If you have treated with Karate, Baythroid, Endigo, Brigade, Bifenthrin, Tombstone, Sniper, Mustang Max, Hero, Proaxis, or Leverage you have treated with a pyrethroid. In our field trials we are having good success controlling worms with relatively low rates of these non-pyrethroids (e.g., Steward at 4.6 oz and Larvin at 10 oz). But even at these rates, the cost is more than the pyrethroids.
From Ames Herbert, Virginia Extension Entomologist
We do not have thresholds for flowering beans but know that high numbers of worms can do too much damage by eating all the flowers which can result in delayed maturity.
What's next for these fields? Will earworms recycle to present another threat to podding fields?
My guess is, yes, at least some percentage of fields may need to be retreated. The decision to retreat should be made based not on rumor, seeing spray rigs running in the neighbor s field, or conversations at the diner, but based on knowledge that thresholds have been met.
Growers cannot afford to make unnecessary sprays, especially with low yield potential and having already paid for one application. And, if a pyrethroid was used the first time we would strongly recommend that these second applications be non-pyrethroids.
If you have treated with Karate, Baythroid, Endigo, Brigade, Bifenthrin, Tombstone, Sniper, Mustang Max, Hero, Proaxis, or Leverage you have treated with a pyrethroid. In our field trials we are having good success controlling worms with relatively low rates of these non-pyrethroids (e.g., Steward at 4.6 oz and Larvin at 10 oz). But even at these rates, the cost is more than the pyrethroids.
From Ames Herbert, Virginia Extension Entomologist
Tobacco Budworm In Mix In Both Soybeans And Peanuts
We have confirmed that tobacco budworm is in both soybean and peanut fields.CLICK HERE to see a table with the percentages of each, corn earworm (CEW)/tobacco budworm (TBW), from 8 fields in Virginia and northeast North Carolina.
Note that the IDs were based on the differences in jaw construction in the two species (mandibular identification), which means the jaws of each worm (240 total) had to be dissected and inspected under high magnification.
Most collections came from fields that had been recently treated by the grower with either Baythroid XL or Karate Z.
We also included the day post treatment that the worms were collected. With the exception of collections from two untreated fields, these worms represent pyrethroid escapes .
Unfortunately, we do not have pre-treatment samples so do not know what the species ratio was prior to application. Escapes ranged from 4 to 86% TBW. Were these selected for by the pyrethroid sprays, as TBW is known to be harder to kill with pyrethroids?
That would be our best guess. In the future, knowing the ratio of CEW/TBW could be critical to achieving good control by guiding the insecticide choice. If TBWs are known to be in the mix, it might tip the scale in favor of using the more effective, but more costly, non-pyrethroids.
In soybeans, that means Steward, Larvin, or Tracer. In peanuts, Steward or Tracer. Soon there may be some new options. Our field plot research is showing a lot of promise for Bayer CropScience s Belt insecticide, Dupont s Coragen insecticide, and a few others. Belt has just received a label for use in soybeans and some other legumes (CLICK HERE for details).
When will this group of products be available and what will they cost? Good questions.
From Ames Herbert, Virginia Extension Entomologist
Note that the IDs were based on the differences in jaw construction in the two species (mandibular identification), which means the jaws of each worm (240 total) had to be dissected and inspected under high magnification.
Most collections came from fields that had been recently treated by the grower with either Baythroid XL or Karate Z.
We also included the day post treatment that the worms were collected. With the exception of collections from two untreated fields, these worms represent pyrethroid escapes .
Unfortunately, we do not have pre-treatment samples so do not know what the species ratio was prior to application. Escapes ranged from 4 to 86% TBW. Were these selected for by the pyrethroid sprays, as TBW is known to be harder to kill with pyrethroids?
That would be our best guess. In the future, knowing the ratio of CEW/TBW could be critical to achieving good control by guiding the insecticide choice. If TBWs are known to be in the mix, it might tip the scale in favor of using the more effective, but more costly, non-pyrethroids.
In soybeans, that means Steward, Larvin, or Tracer. In peanuts, Steward or Tracer. Soon there may be some new options. Our field plot research is showing a lot of promise for Bayer CropScience s Belt insecticide, Dupont s Coragen insecticide, and a few others. Belt has just received a label for use in soybeans and some other legumes (CLICK HERE for details).
When will this group of products be available and what will they cost? Good questions.
From Ames Herbert, Virginia Extension Entomologist
Corn Earworm Trap Counts Remain High
In general, nightly black light trap captures of corn earworm moths remained high this week.
Please see the PDF for more details
Please see the PDF for more details
Local Corn Earworm Populations Again Demonstrating High Levels Of Pyrethroid Resistance
Dr. Ames Herbert, Extension Entomologist, mentioned in his July 29, 2010, advisory that we are continuing to monitor for pyrethroid resistance in corn earworm.
We have now tested over 1,500 moths and are averaging 28% survival in the 5 ug cypermethrin vials (see the data by clicking here).
This is now the third consecutive year that local corn earworm populations are demonstrating high levels of pyrethroid resistance. As Dr. Herbert said in his advisory, proceed with caution and consider non-pyrethroids especially in peanut or soybean fields with a lot of worms.
- From Sean Malone, Tidewater Agricultural Research
We have now tested over 1,500 moths and are averaging 28% survival in the 5 ug cypermethrin vials (see the data by clicking here).
This is now the third consecutive year that local corn earworm populations are demonstrating high levels of pyrethroid resistance. As Dr. Herbert said in his advisory, proceed with caution and consider non-pyrethroids especially in peanut or soybean fields with a lot of worms.
- From Sean Malone, Tidewater Agricultural Research
Corn Earworm Increasing On The Eastern Shore
Corn earworm still seems to be the pest to watch right now.
Numbers seem to be high to the south of us and increasing on the Shore. Continue to monitor fields for theshold numbers before spraying as worm pressure is heavy in some locations and low in others.
Fall army worm pressure on the station seems to be dropping, although some small worms were seen, possibly indicating the beginning of a second generation.
Beet army worm flights continue to be high in the traps, but few worms have been seen in the field. Trap numbers seem to be skewed possibly due high thunderstorm activity during the evenings keeping flight counts low. See this week's table.
From Thomas Kuhar, Entomologist, Eastern Shore Agricultural Research & Extension Center
Numbers seem to be high to the south of us and increasing on the Shore. Continue to monitor fields for theshold numbers before spraying as worm pressure is heavy in some locations and low in others.
Fall army worm pressure on the station seems to be dropping, although some small worms were seen, possibly indicating the beginning of a second generation.
Beet army worm flights continue to be high in the traps, but few worms have been seen in the field. Trap numbers seem to be skewed possibly due high thunderstorm activity during the evenings keeping flight counts low. See this week's table.
From Thomas Kuhar, Entomologist, Eastern Shore Agricultural Research & Extension Center
Belt Insecticide Approved For Soybeans, Other Legumes
Belt SC (flubendiamide) has just received EPA approval for use in soybean and legume vegetables (including edible-podded and succulent shelled pea and bean, dried shelled pea and bean and foliage of legume vegetables).
For controlling worm pests in soybean, the rate will be 2 to 3 oz/acre, 10 gpa minimum by ground, with a 14 day pre-harvest interval.
Belt provides a unique mode of action against lepidoteran larvae and will fit well as another non-pyrethroid option (in addition to Steward, Tracer and Larvin) in soybean. We have tested Belt at the 3 oz rate in four soybean field trials since 2008 and found that it works well against corn earworm.
From Ames Herbert, Virginia Extension Entomologist
For controlling worm pests in soybean, the rate will be 2 to 3 oz/acre, 10 gpa minimum by ground, with a 14 day pre-harvest interval.
Belt provides a unique mode of action against lepidoteran larvae and will fit well as another non-pyrethroid option (in addition to Steward, Tracer and Larvin) in soybean. We have tested Belt at the 3 oz rate in four soybean field trials since 2008 and found that it works well against corn earworm.
From Ames Herbert, Virginia Extension Entomologist
Friday, August 6, 2010
Pest Treatment Activity Picks Up On Eastern Shore
From Tom Kuhar, Virginia Tech Entomologist, Eastern Shore REC, Painter, Va.
Many full-season soybeans on the Eastern Shore of Virginia were sprayed for insect pests this week.
In many cases, these sprays were needed as pest numbers of spider mites, corn earworms, green cloverworms and other caterpillar pests were high. In the fields that I inspected, I saw a lot of green cloverworm, corn earworm, yellowstriped armyworm and some beet armyworms.
I did not see soybean loopers, which often are hard to kill.
Beet armyworms have also shown resistance to pyrethroids in past trials on the Eastern Shore.
A number of different insecticides were applied. Some growers sprayed Steward to combat the complex of caterpillars, while some others sprayed Orthene and a pyrethroid, such as Warrior, to combat the mix of pests. Other growers sprayed a generic Lorsban 4E, which provided efficacy against the spider mites as well as the caterpillar pests, including beet armyworms.
Let's hope our growers do not have to spray again, as these sprays were applied early in the crop, and we've still probably yet to see the major flight of corn earworms that attack the pods.
Many full-season soybeans on the Eastern Shore of Virginia were sprayed for insect pests this week.
In many cases, these sprays were needed as pest numbers of spider mites, corn earworms, green cloverworms and other caterpillar pests were high. In the fields that I inspected, I saw a lot of green cloverworm, corn earworm, yellowstriped armyworm and some beet armyworms.
I did not see soybean loopers, which often are hard to kill.
Beet armyworms have also shown resistance to pyrethroids in past trials on the Eastern Shore.
A number of different insecticides were applied. Some growers sprayed Steward to combat the complex of caterpillars, while some others sprayed Orthene and a pyrethroid, such as Warrior, to combat the mix of pests. Other growers sprayed a generic Lorsban 4E, which provided efficacy against the spider mites as well as the caterpillar pests, including beet armyworms.
Let's hope our growers do not have to spray again, as these sprays were applied early in the crop, and we've still probably yet to see the major flight of corn earworms that attack the pods.
Threshold Levels of Bollworms Found in Conventional Cotton
From Ames Herbert, Virginia Extension Entomologist
We are finding threshold levels of bollworms (eggs and live worms) in conventional cotton (no Bollgard2 or Widestrike). Those fields should be managed using the old system (treat at egg threshold and retreat in 5-7 days). The best approach for Bollgard2 and Widestrike cotton is the treat one time 5-7 days after the egg threshold, which targets any escaped worms. Not treating Bollgard2 or Widestrike cotton could be a mistake. For the past 2 years, we have seen as much as 2-3% boll damage in some Bollgard2 varieties, and as much as 10% damage in one Phytogen variety. A single pyrethroid application (highest labeled rate) cleaned up the problem.
One cautionary note, we have gotten reports of worms escaping pyrethroid treatments in cotton.
One cautionary note, we have gotten reports of worms escaping pyrethroid treatments in cotton.
Corn Earworm Outbreaks In Soybeans: Early and Heavy in Some Fields, Not in Others
From Ames Herbert, Virginia Extension Entomologist
Corn earworm has moved into soybean fields across much of Virginia. This is earlier than normal and most are faced with the decision to treat (or not) flowering stage beans. Infestation levels vary a lot from field to field from almost no worms in lush canopy fields, to drought stressed open canopy fields with as many as 25+ per 15 sweeps.
Although we have decent thresholds for foliage feeding and pod feeding, there is little guidance as to the impact of flower feeding by corn earworms. Several years ago researchers in North Carolina (Eckel et al. 1992) concluded that flower feeding contributed to yield reductions by delaying pod set, but no exact thresholds were developed. Without good guidelines as to how many can be tolerated, we are suggesting that low to moderate numbers (6 or less medium plus large worms/15 sweeps) could be safe, especially if beans are growing well with good soil moisture. More than that may represent a threat. Again, just a grab.
We are also getting a lot of calls from folks finding live worms after pyrethroid sprays, in cotton, peanut and soybean fields. Most are using either Karate Z or Baythroid XL and the misses are about equal among the products. The most obvious cases are where there were very high numbers of worms so the survivors are still quite noticeable.
We visited one field that had been sprayed 24 hours earlier and found an average of about 4 to 8 worms/15 sweeps. Since it was still not forming pods, I suggested that it not be retreated, yet. Of course, any field that has been treated will be very susceptible to any subsequent infestations, as beneficial insects would have been mostly eliminated so be sure to begin re-scouting 7 days after the last application. If another treatment is needed, strongly consider a non-pyrethroid.
We are also seeing a mix of worm species including yellow striped armyworms, green cloverworms, and maybe some tobacco budworms. Corn earworm is still the primary species, so I would direct the spray program to those.
Corn earworm has moved into soybean fields across much of Virginia. This is earlier than normal and most are faced with the decision to treat (or not) flowering stage beans. Infestation levels vary a lot from field to field from almost no worms in lush canopy fields, to drought stressed open canopy fields with as many as 25+ per 15 sweeps.
Although we have decent thresholds for foliage feeding and pod feeding, there is little guidance as to the impact of flower feeding by corn earworms. Several years ago researchers in North Carolina (Eckel et al. 1992) concluded that flower feeding contributed to yield reductions by delaying pod set, but no exact thresholds were developed. Without good guidelines as to how many can be tolerated, we are suggesting that low to moderate numbers (6 or less medium plus large worms/15 sweeps) could be safe, especially if beans are growing well with good soil moisture. More than that may represent a threat. Again, just a grab.
We are also getting a lot of calls from folks finding live worms after pyrethroid sprays, in cotton, peanut and soybean fields. Most are using either Karate Z or Baythroid XL and the misses are about equal among the products. The most obvious cases are where there were very high numbers of worms so the survivors are still quite noticeable.
We visited one field that had been sprayed 24 hours earlier and found an average of about 4 to 8 worms/15 sweeps. Since it was still not forming pods, I suggested that it not be retreated, yet. Of course, any field that has been treated will be very susceptible to any subsequent infestations, as beneficial insects would have been mostly eliminated so be sure to begin re-scouting 7 days after the last application. If another treatment is needed, strongly consider a non-pyrethroid.
We are also seeing a mix of worm species including yellow striped armyworms, green cloverworms, and maybe some tobacco budworms. Corn earworm is still the primary species, so I would direct the spray program to those.
Friday, July 30, 2010
Virginia: Corn Ears Infested With Bollworms - Indicator Of Spraying Trends In Cotton - Hit 42%
By D. Ames Herbert, Jr., Extension Entomologist, Virginia Tech Tidewater AREC
Annually, we conduct a survey to estimate Helicoverpa zea (bollworm/corn earworm) infestation levels in field corn in late July.
Corn is considered a nursery crop for earworm, allowing the pest to complete a lifecycle and then move on to other crops such as soybean, cotton, and peanut in August.
Over 30 years of data show that there is nearly a 1:1 relationship between the infestation level in corn and the amount of soybean acreage that gets treated with insecticide for this pest. This means that if 50% of corn ears are infested, we can expect about 49.9% of Virginia’s soybean acreage to be treated for earworm.
Corn is considered a nursery crop for earworm, allowing the pest to complete a lifecycle and then move on to other crops such as soybean, cotton, and peanut in August.
Over 30 years of data show that there is nearly a 1:1 relationship between the infestation level in corn and the amount of soybean acreage that gets treated with insecticide for this pest. This means that if 50% of corn ears are infested, we can expect about 49.9% of Virginia’s soybean acreage to be treated for earworm.
To conduct the survey this year, the number of corn earworms found in 50 ears of corn was recorded in 5 randomly selected corn fields in each of 24 counties, totaling 5,800 ears and 116 fields sampled.
When fields were known to contain Bt or non-Bt corn, this was noted.
Otherwise, samples were considered to be random and assumed to be representative of the actual Bt/non-Bt composition in each county. Age of earworms, or if they had already exited the ears, was also recorded.
We greatly appreciate the help of Virginia Cooperative Extension Agriculture and Natural Resource (ANR) Agents, Virginia Tech faculty and staff, and volunteers in this effort. These cooperators are acknowledged at the end of this report. We also would like to thank the many growers who graciously allowed us to inspect their fields for earworm.
CLICK HERE for a breakdown of the surveyresults..
When fields were known to contain Bt or non-Bt corn, this was noted.
Otherwise, samples were considered to be random and assumed to be representative of the actual Bt/non-Bt composition in each county. Age of earworms, or if they had already exited the ears, was also recorded.
We greatly appreciate the help of Virginia Cooperative Extension Agriculture and Natural Resource (ANR) Agents, Virginia Tech faculty and staff, and volunteers in this effort. These cooperators are acknowledged at the end of this report. We also would like to thank the many growers who graciously allowed us to inspect their fields for earworm.
CLICK HERE for a breakdown of the surveyresults..
- Statewide, 42% of ears were infested with earworms. This is up from 36% in 2009.
- Regional averages were 12% infested in Northern, 28% in the Northern Neck, 39% in Mid-Eastern, 58% in the Southeast, and 46% on the Eastern Shore.
- From the survey, it looks like the areas of greatest risk to heavy infestations of earworms are the southeastern ‘cotton/peanut’ counties and the Eastern Shore. However, as large as this effort is, it is not a complete picture.
- We always recommend scouting individual fields to determine exactly what is happening in terms of corn earworm as well as other pests and crop problems. In a lot of this year’s samples, earworms had already exited from the ears to pupate, which indicates that the process may be a little ahead of schedule.
- Moths have already begun to emerge from corn fields and the main flight has begun (see our weekly black light trap catches for more details). We are currently conducting an earworm trial in a heavily infested soybean field in Jackson, North Carolina.
- We will continue posting moth catch numbers and other information regarding the 2010 insect pest situation.
Trying To Get A Handle On Bollworm-CEW Pyrethroid Survivorship
From D. Ames Herbert, Jr., Extension Entomologist, Virginia Tech Tidewater AREC
As of July 29, we have tested a total of 768 corn earworm moths in our pyrethroid AVT (adult vial testing) program.
Although the percent survivorship is down somewhat from last week, we are still seeing greater than 20% survive (see the line graph).
Could this mean that field failures are likely?
Possibly, especially if worm populations are large. Our goal is to process as many moths as we can and post these weekly updates. We are also responding to calls from crop consultants, advisors and growers.
We have one reported case of a less-than-acceptable level of control in a peanut field. Could some of those surviving worms have been tobacco budworms, which are known to be more difficult to control with pyrethroids? Possibly, but it is almost impossible to distinguish between corn earworm and tobacco budworm without inspecting the moth parts of the worms under magnification in lab.
We do know that budworms can be in the mix, up to 30% one year when we did a lot of worm IDs.
Bottom line, this is the third consecutive year that local corn earworm populations are demonstrating high levels of pyrethroid resistance. Proceed with caution and consider non-pyrethroids especially in peanut or soybean fields with a lot of worms.
As of July 29, we have tested a total of 768 corn earworm moths in our pyrethroid AVT (adult vial testing) program.
Although the percent survivorship is down somewhat from last week, we are still seeing greater than 20% survive (see the line graph).
Could this mean that field failures are likely?
Possibly, especially if worm populations are large. Our goal is to process as many moths as we can and post these weekly updates. We are also responding to calls from crop consultants, advisors and growers.
We have one reported case of a less-than-acceptable level of control in a peanut field. Could some of those surviving worms have been tobacco budworms, which are known to be more difficult to control with pyrethroids? Possibly, but it is almost impossible to distinguish between corn earworm and tobacco budworm without inspecting the moth parts of the worms under magnification in lab.
We do know that budworms can be in the mix, up to 30% one year when we did a lot of worm IDs.
Bottom line, this is the third consecutive year that local corn earworm populations are demonstrating high levels of pyrethroid resistance. Proceed with caution and consider non-pyrethroids especially in peanut or soybean fields with a lot of worms.
Eastern Shore Insect Trap Counts for Week ending July 29
This week the corn ear worm flight seems to have spread throughout both counties with all trap locations showing increased activity.
This week also showed a jump in beet armyworm catches at both the Eastville and Painter locations while cornborer activity has shown a significant decrease.
Click more to view a spreadsheet of pheromone trap catch and blacklight trap catch from various locations on the Eastern Shore. [More]
-- Tom Kuhar, Virginia Tech Entomologist
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