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.
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