Author Archives: Ames Herbert

Map of Virginia showing counties with kudzu bugs.

Soybean kudzu bug update—July 24, 2014

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Our scouts have reported finding kudzu bugs in soybean fields in 4 counties.  Nymphs as well as adults were found in two of those counties, Lunenburg and Prince William.   Adults and nymphs were found in kudzu, only, in two other counties.  All are near the southern border of the state.  We are expecting this to change pretty rapidly so we strongly recommend that you start checking fields.  This is most easily done with a sweep net.  Go to several areas of a field, especially along the edges, and do several 15 sweep samples.  At this point in the season, treatment thresholds should be based on the 1 nymph/sweep threshold.

Cotton stink bug scouting card

Cotton stink bug update—July 24, 2014

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We are finding (and hearing about) a few cotton fields that have reached or exceeded stink bug damage thresholds—not all by any means, but some. For the most part, these are fields in the 3rd or 4th weeks of bloom.  If you are following our recommended cotton stink bug thresholds, the threshold for the 3rd, 4th and 5th weeks of bloom is 10 percent internal stink bug damage.  The research that these thresholds are based on showed that these weeks are the most critical for boll production and the bolls present during this period are the most susceptible to stink bug feeding injury.

If you have not started checking fields for stink bug damage to bolls, you might want to consider starting.  In each field, pull a random sample of at least 25 bolls that fit in the ‘holes’ in our scouting card (contact us or your local extension office if you need a stink bug scouting card).  Using bolls in this size range guarantees that you are sampling the right boll population.  Crack each boll and inspect for internal stink bug feeding injury symptoms.

What products will give you the best control of stink bugs and longest residual activity?  Our field trials, and others, show pretty consistently that pyrethroids and products like Bidrin provide the best control.  Insecticides in the neonicotinoid class, if applied alone, are weak.  Although products do a decent job of killing the adults and nymphs, none provide much residual activity —even 7 days would be a stretch.  If adult stink bugs continue move in to field, more than one application may be needed.

IMPORTANT—New Name and Transitioning to an Updated Delivery System

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After 12+ years, the Virginia Ag Pest Advisory has been ‘modernized’. As of this week, it will be transitioned to a new format, powered by WordPress and MailChimp software. We are also adding new authors to cover crop updates so are changing our name to the Virginia Ag Pest and Crop Advisory.

As with the old system, you will still receive weekly emails containing important advisories on your mobile or desktop device, and as before, you can scroll the titles and select only those that are important to you. Normal advisories will be delivered each Friday at 1 am and available for reading first thing on Friday mornings. And as before, there is an ‘Urgent’ option that will be used to provide any advisories that need immediate attention.

In addition, all advisories will be posted to the new Blog site: http://blogs.ext.vt.edu/ag-pest-advisory. You may want to ‘bookmark’ this url. If you are not currently on the old Virginia Ag Pest Advisory email recipient list and want to be added, the Blog site provides an easy way for you to do that.

We hope you will be pleased with our new advisory system.

Thanks,
Ames Herbert

Where are the kudzu bugs–soybean update

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The big question today is—where are the kudzu bugs we expected to see in our soybean crop? As of this week, we have not seen any adults or nymphs in the early planted full season crop. In fact, the same situation is being reported for much of the eastern US. Dominic Reisig at NCSU says that even in NC, the only reported infestations are from southernmost counties.

Last summer by this time we were seeing many full season early planted files with infestations of adults that have moved from adjacent overwintering sites. The only bugs we have found so far have been in kudzu patches. So, what’s the difference in years and why the delayed movement of adults? All we can say is that it must be related to the colder than normal temperatures we experienced during the winter. We know that in the Suffolk area there were at least two nights when temperatures dropped below zero (æF), and of course it was even colder north and west of us. Could those cold temperatures have killed some of the overwintering adults reducing the overall population levels?

We do know from our adult overwintering emergence traps that were placed throughout much of the state that adults survived and emerged this April and May in about 12 counties in the southern part of the state. Why they did not move into early planted soybean fields is another unanswered question.

From what I can gather from reading and talking with other entomologists in the southeast, 2014 is shaping up to be similar to 2011 when the first generation of kudzu bugs developed in kudzu (mostly) and other alternate hosts and only the second generation moved into soybean fields. This certainly seems to be what is happening this year. In some ways this scenario, if it plays out, will simplify the field scouting and threshold determination. The ‘original’ kudzu bug threshold developed in the southeast was based on this second generation that moved into reproductive stage (flowering—early pod) soybean fields—and it is based on number of nymphs (see below). We have initiated our 2014 soybean insect pest survey so will be reporting updates as they come in so stay tuned.

Treatment Thresholds for 2nd Generation Kudzu Bugs, Nymphs Present

Sweep Net
” An average of 1 nymph/sweep, 15/15 sweeps
” Take at least ten 15-sweep samples to represent the entire field
” Sampling should not be biased by sampling close to field edges where populations may by congregated
Canopy Observation
” At least 10 observation spots representing the entire field
” Nymphs easily found on main stems, leaf petioles or leaves

Where are the kudzu bugs? — soybean update

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The big question today is where are the kudzu bugs we expected to see in our soybean crop? As of this week, we have not seen any adults or nymphs in the early planted full season crop. In fact, the same situation is being reported for much of the eastern US. Dominic Reisig at NCSU says that even in NC, the only reported infestations are from southernmost counties. Last summer by this time we were seeing many full season early planted files with infestations of adults that have moved from adjacent overwintering sites. The only bugs we have found so far have been in kudzu patches. So, what’s the difference in years and why the delayed movement of adults? All we can say is that it must be related to the colder than normal temperatures we experienced during the winter. We know that in the Suffolk area there were at least two nights when temperatures dropped below zero (æF), and of course it was even colder north and west of us. Could those cold temperatures have killed some of the overwintering adults reducing the overall population levels? We do know from our adult overwintering emergence traps that were placed throughout much of the state that adults survived and emerged this April and May in about 12 counties in the southern part of the state. Why they did not move into early planted soybean fields is another unanswered question. From what I can gather from reading and talking with other entomologists in the southeast, 2014 is shaping up to be similar to 2011 when the first generation of kudzu bugs developed in kudzu (mostly) and other alternate hosts and only the second generation moved into soybean fields. This certainly seems to be what is happening this year. In some ways this scenario, if it plays out, will simplify the field scouting and threshold determination. The original kudzu bug threshold developed in the southeast was based on this second generation that moved into reproductive stage (flowering early pod) soybean fields and it is based on number of nymphs (see below). We have initiated our 2014 soybean insect pest survey so will be reporting updates as they come in so stay tuned. Treatment Thresholds for 2nd Generation Kudzu Bugs, Nymphs Present Sweep Net ” An average of 1 nymph/sweep, 15/15 sweeps ” Take at least ten 15-sweep samples to represent the entire field ” Sampling should not be biased by sampling close to field edges where populations may by congregated Canopy Observation ” At least 10 observation spots representing the entire field ” Nymphs easily found on main stems, leaf petioles or leaves.

Reports of Lygus bugs in cotton—a false alarm for Virginia

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There is a lot of conversation about the big Lygus bug outbreaks in northeast North Carolina cotton, and that the pest is moving north. The first part is true. There are areas in NC that are experiencing Lygus bug pressure, especially in their eastern blacklands and in cotton fields near potato fields. The second part is not true. Lygus bugs do not migrate from south to north but are a localized pest that moves from host plant to host plant based on factors like—when the alternate host plants dry down (like weeds) or are harvested (like potatoes).
First, let’s be sure we know what bug we are talking about. Lygus lineolaris, or tarnished plant bug (a. k. a. —Lygus bug or plant bug) is a very common insect in our area. Small numbers of adults and nymphs can be found on almost any weed or crop that flowers. It is a small insect, about ¼ the size of an adult green or brown stink bug, that feeds in a similar manner to stink bugs by inserting its small beak into squares and bolls to extract plant fluids. Feeding can kill small squares and cause stink bug-like injury symptoms to small bolls. Lygus bugs can be a sever pest of cotton in some areas of the US like the Delta and Mid-south cotton states where growers battle this pest with 4 to 8 or more sprays each year. Infestation levels in the eastern states have always been much, much lower. Jack Bacheler, before he retired from NC State, used to quote total percentage cotton acreage treated annually for Lygus bugs to be on average only about 1 – 2 percent. In Virginia, I have only encountered or heard about a very few fields that were infested at levels that warranted treatment. The most recent was last summer on our Eastern Shore where a cotton field next to a potato field was damaged extensively when the Lygus bugs migrated out of the potatoes after they were dug. This is a ‘classic’ case, and one that occurs a lot in the potato production area of northeast North Carolina.
So, this ‘mysterious’ Lygus bug pest is not—mysterious, that is. We understand it, and we have good methods for determining if it is a real threat to a field. To scout for Lygus bugs you need to 1) check for missing squares (percent square retention), and 2) check for presence of adults or nymphs. Neither alone will give you the whole picture. You need to do both—check for missing squares, and check to see if bugs are active. Checking for only missing squares can mislead you because other stresses in the environment can cause small squares to shed (e.g., extreme heat, drought, periods of cloudy weather). Documenting the presence of Lygus bugs does not give the whole picture either because adults are extremely mobile and can rapidly move in and out of fields. Sometimes they may be present, but not causing square injury or loss.
Weekly checks of upper square retention is the most efficient way to assess if Lygus bugs can either be ruled out as an economic concern at that time or if sweep netting for the adults and nymphs is needed. An upper square retention rate of 80% or more usually indicates that Lygus bugs are not present at damaging levels. In most years in Virginia, percent square retention is very high – often in the mid to upper 90’s. A recent (July 1 and 2, 2014) check of 8 randomly selected fields showed they had greater than 95% square retention. If upper square retention is less than 80%, you should use a sweep net to sample in eight to 10 locations in the field away from the edge, looking for live adult and immature Lygus bugs. If a field has less than 80% square retention and an average of eight Lygus bugs per 100 sweeps, a spray is needed at that time. Remember that when cotton is approximately one week into blooming, a five-foot black beat cloth is a more accurate sampling devise than the sweep net for Lygus bug, especially the nymphs which show up as almost florescent green on the black cloth background.
If a threshold is met and a treatment is needed, here is an example of a spray plan shared by NC State. For the first Lygus bug spray pre-bloom, at squaring or first flower, consider using a stand-alone neonicotinoid product (common examples include Admire Pro, Belay, Centric, Intruder, Trimax Pro). These are generally softer on beneficial insects so conserve them. If Lygus bugs are still a concern later on, or require a second spray, first check to see that aphids are not common in the field. We have been lucky in VA with having very little aphid pressure in cotton in the last few years, but if aphids are present, you should not use a neonicotinoid again. Switch to a product like Carbine, Transform, or one of the more effective pyrethroids. If aphids are not a concern, you should still not use a stand-alone neonicotinoid product for a second spray, but should switch to one of the pre-mixed products (like Endigo, Leverage, Swagger, etc.) that also contain a pyrethroid, or an organophosphate/carbamate-only product (like Bidrin, Orthene, Vydate, etc.). Many of these products are also effective against stink bugs; eliminating stink bugs can be beneficial during the period of boll formation. The downside to these products is that they kill beneficial insects and put the field at higher risk for bollworm and spider mites—so if any of these products is used, be sure to scout these fields later in the season.

Peanut worm pest advisory

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Beet armyworms and tobacco budworms occurring in GA and SC peanut fields, and corn earworm moths are starting to show up in VA
We are getting reports of infestations of both beet armyworm and tobacco budworm in peanut fields in Georgia and South Carolina. These are pretty early reports and could signal trouble to come. Although we get both species in this area of Virginia, it has been several years since we have experienced severe infestations of either.
Beet armyworms seem to be cyclic, occurring only once every few years, with no pattern that we understand. Moths migrate into the area from the south and are particularly attracted to pigweed species. Often the caterpillars will be found feeding on pigweeds on field edges, or wherever the weeds are growing. They feed on pigweed plants then move to nearby crop plants. So peanut (cotton or soybean) fields bordered by a lot of pigweeds or with a lot weeds in the field are particularly vulnerable to beet armyworm infestations.
Tobacco budworm is known to be an occasional pest of cotton, peanuts and soybeans in this area. Caterpillars are easily confused with corn earworm, a different but related species. Adult moths of these species look very different, but the caterpillars are almost identical except for features that require some knowledge and good magnification. We separate these species holding large sized caterpillars under a microscope and inspecting the shape of the mandibular ridge (the inside ‘jaw’ of the mouthparts). Obviously this is not something that can be done in the field.
Budworms are not a big threat to peanuts or soybean, as they are leaf feeders, only, and it takes a lot to do economic damage. They do no more damage than corn earworm, the more common of the two species. In peanut and soybean fields, both budworm and corn earworm can occur at the same time, but typically corn earworm is the dominant pest making up 70 percent or more of the total. In cotton budworms can be troublesome as they feed on young developing squares. Another difference between these species is the timing of the infestation. In some years we see budworm infestations early, before corn earworm. This seems to be the case this year, at least in states south of us.
Corn earworm moths are starting to show up in VA. We are catching 10-20 per night in our local pheromone traps which isn’t a lot in comparison to what we will see later in the season, but enough to result in some possible small outbreaks of worms.
Beet armyworm, tobacco budworm, and corn earworm are strictly leaf feeders in peanut so any decision to treat a field should be based on 1) the number of worms per row foot, and 2) the degree of defoliation compared to the total foliage of the canopy. The threshold for ‘worms’ for this time of year is 4 per row foot (total, all species). If you sample using a drop cloth, after slapping plants on both sides of a 3 foot long cloth you would need to see at least 12 worms. The likeliness of actually finding this many worms is very low&that is&it is pretty rare to find threshold levels of worms in any peanut field.
But is always pays to be vigilant. Check fields periodically throughout the season for pests. If after checking you find at or near thresholds of any pest, select a product that fits the need. If for example you do find a field at threshold for a combination of beet armyworm, tobacco budworm, or corn earworm pyrethroids would not be the best choice. These species would be controlled better with non-pyrethroids like Steward, Belt, Prevathon, or Blackhawk.

Cotton/Peanut Thrips update, May 29, 2014

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Thrips pressure ramped up very quickly over the past Memorial Day weekend.

COTTON: In our cotton plots, we’re getting counts of over 100 immatures in some of our 5-plant seeding samples, and injury has reached extreme levels in untreated cotton. So, who cares about data from untreated cotton? I do. These data provide a ground-truth indicator of 1) how the thrips populations compare over the years, and 2) what amount of injury (symptoms) and damage (lint loss) they are capable of causing. We maintain untreated ‘controls’ in our tests for these reasons. Depending on the planting date, variety and soil conditions, the injury in this year’s untreated controls is now ranging from 2.5 of so (on our 0-5 scale) to 4.85 (many plants killed or severely injured). Earlier planted cotton has the most injury and we see more in fields with ‘heavier’ soils. Adult thrips are still present on the plants which tells us that the infestation cycle is not over. Based on past experience, I think the peak will occur next week. So if you have not treated for thrips, now would be a very good time to check fields and make the call. If you see any significant number of seedlings showing injury, especially if the new buds are injured, blackened and deformed, now is the time to treat.

Many treatments in our cotton plots are providing excellent protection. For the most part, seed treatments are not providing the same level of protection as liquid in-furrow treatments. If you are relying on seed treatments, there is a good chance your cotton could benefit from a foliar treatment. The higher rates of the liquid in-furrow treatments are holding well and may not need additional foliar treatments, depending on how fast plants grow to the 3-4 leaf thrips-safe stage.

PEANUTS: Thrips populations are slower to develop in peanuts but untreated plants are beginning to showing significant levels of injury (up to 3.0 on our 0-10 injury scale). There are a lot of adult thrips on peanut seedlings which tells us that the cycle is still in progress and things will get worse over the next couple of weeks, for sure. As in our cotton plots, the seed treatments are showing more injury compared with liquid in-furrow treatments and may need more protection. The decision is not as urgent in peanuts, compared with cotton, as peanuts seem to tolerate thrips injury better—but, there is a point when more protection is a benefit. It is has been hard to pin this down—but in general if I see more 25-30% of the leaves with injury (crinkled leaves) and, especially, if the new terminal leaves are brown and deformed, it is time to apply a foliar treatment.

EARLY SEASON FIELD TOUR—NEXT WEEK—JUNE 5
If you are interested in getting a look at our cotton and peanut thrips trials, or field presentations by our other Tidewater AREC faculty, take advantage of the opportunity to attend our annual Early Season Field Tour Thursday of next week June 5. Registration begins at 8:30am at our Hare Road Farm and we will conclude with a nice lunch. CCA recertification credits will be offered, as well as credits for Private Applicators, Commercial Applicators 1-A, 1-C and 10) and Registered Technicians. Email or call if you need more information (herbert@vt.edu; 757-657-6450).

Thrios infestation update

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Thrips infestation update
A quick update. We began sampling cotton and peanut seedlings this week for thrips. We take cotton plants or peanut leaflets from field plots, rinse the adult and immature thrips into lab dishes, and count them under a scope.
We are at the beginning of the infestation and seeing just a few adults on plants—less than one adult per plant on cotton seedlings and less than one per leaflet in peanut. We see even fewer immatures, with one exception–in some cotton that was planted very early during the last week in April. Those plants have pretty high numbers of immatures—around 20 per plant. We are just beginning to see the visual symptoms of the feeding injury—not enough yet to do ratings.
In general the infestation is a little behind compared to most years due to the cooler spring/early summer temperatures, but I expect we will see more immatures next week and more injury. Even though the infestation seems a little delayed, I would stay with our recommended treatment schedule. If a foliar application is needed, I would still target the early first true leaf stage. Treating when seedlings are in that stage has almost always given us the best results—stay with the plan.
We will begin providing weekly updates on thrips and other insect pests as the season progresses—so stay tuned.

Be careful if you are planning to tank mix Admire Pro with a starter/pop-up liquid fertilizer

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Admire Pro applied as a liquid into the seed furrow is proving to be an excellent option for controlling thrips in cotton and peanuts. To increase efficiency, growers are beginning to look at the options for tank mixing other planting time products with the Admire Pro including different starter/pop-up liquid fertilizers. We have information that suggests that there are some combinations that are not working well.

For example, we did a field trial last summer and found that Admire Pro did NOT mix well with 10-34-0 (N-P-K). Where Ca(NO3)2 tank mixed with the Admire Pro with no problem and provided good seedling vigor and good thrips control, the 10-34-0 (N-P-K) Admire Pro tank mix did not. The Admire Pro 10-34-0 mix clotted up and caused clogginh of sprayer lines and nozzle screens. Not unpredictably, seedling vigor and thrips control were also compromised.

We recently had the same experience with a local grower. Before (thankfully) adding Admire Pro to a full load of 3-15-19, (N-P-K) starter/pop-up fertilizer we did a ‘jar’ test. We saw the same result as we did the previous summer in our field trial—that the Admire Pro clotted up in the jar and quickly precipitated out in whitish flakes to the bottom of the jar—not good.

We are beginning a project to evaluate other fertilizer products in lab ‘jar’ test mixes and will take some of these to the field this summer to look at how these mixes perform, both in terms of seedling growth enhancement and thrips control. In the meantime we STRONGLY recommend that if you are planning to tank mix Admire Pro with a starter/pop-up fertilizer that you do a ‘jar’ test to check for compatibility. And, based on our experiences, when filling the spray tank you should add the water first, then the fertilizer, then the Admire Pro last. Continual tank agitation may also be helpful to minimize the risk of any settling of the suspension.

Ames Herbert and Hunter Frame, VT, Tidewater AREC