Nothing is really hot this week in terms of insect pests. We are seeing a few potato leafhoppers in peanuts but not heavy or widespread. We are concerned about the early results of our annual program for monitoring corn earworm pyrethroid susceptibility, but this issue is covered in detail in another of today’s advisories. In soybeans, we are hearing of more than usual numbers of fields with 3-cornered alfalfa hoppers girdling seedlings. This is a tough insect to make a call on in terms of when to pull the trigger. We have documented some feeding by Asiatic garden beetle in cotton (see attached image slide collection) in one county in the northern part of our cotton area. I noticed that Dominic Reisig at NCSU commented on seeing some of the same in his state. This is a new pest of cotton and we do not know much about it. If the damage is limited to the adults feeding on leaves, we can handle it with some fairly decent guesses as to how much leaf feeding seedlings can tolerate before a treatment is needed. If you view the attached images, you will see some seedlings in the infested area were completely striped of leaves. Will this slow these plants down? Hard to say. This damage will likely not be as damaging as the feeding by thrips that concentrates on the developing bud. But we also know that Asiatic garden beetle grubs can do significant amounts of root feeding. Are they feeding on cotton roots? Would the common cotton insecticide seed treatments offer any protection? All good questions with no immediate answers. This outbreak does tell us that we should be more vigilant when it comes to scouting cotton fields during the period from post-thrips to early squaring. Additional information: asiatic-garden-beetle-cotton-king-queen-va-2012-pptx

As of the end of this week (June 29, 2012) we have tested 372 corn earworm (CEW) moths for pyrethroid susceptibility and have a season average of 31.2% surviving the AVT (adult vial test) challenge (see the attached line graph). We had one sample with over 40% survivorship. These are high numbers for the beginning of the season and compare pretty well to what we had at this time in 2011, if not a bit higher. What does this tell us? We cannot claim ‘pyrethroid resistance’ based on this kind of random survey of moths, but historically, when we see survival numbers of about 25-30% or higher, we can expect some pyrethroid control problems, especially if moth fights are heavy, and the weather turns dry. That combination would almost guarantee control problems. But, if CEW populations reach only low to moderate numbers and the season continues to get plenty of rainfall, field failures will not be nearly as common. With loss of Larvin, an effective non-pyrethroid for controlling CEW, growers will need to turn to other non-pyrethroids like Belt, Coragen (Prevathon**), Steward, or combinations that include a pyrethroid plus a non-pyrethroid either tank mixed (like a pyrethroid + Orthene) or as a product (like Besiege** which contains Karate and Coragen). (**note, the registration status of these products is not certain at this point)
Additional information: va-cew-avt-results-6-28-12-pptx

This week’s black light trap catches of corn earworm moths and brown marmorated stink bugs remain low. Average nightly corn earworm catches were: Warsaw-0.2, Petersburg-1.1, Southampton-0.4, Suffolk-1.1, Chesapeake-1.0. Nightly BMSB catches were: Warsaw-0.3, Petersburg-0.3, Southampton-zero, Suffolk-zero, Chesapeake-zero. Thanks to Mary Beahm, Mark Kraemer, Chris Drake, Ames Herbert, and Watson Lawrence for their reports this week.

We have finally passed through our roughest thrips pressure weeks, although we are still getting a few questions about Thimet burn in peanuts. Looking back, the consequences of the thrips pressure will vary a lot depending on where you are in the state. The southeastern most cotton areas typically sustained heavier pressure and had more plant damage. The pressure seemed generally less in the western areas. As mentioned earlier, pressure in cotton generally happened earlier and was much greater compared with peanut. Overall, peanuts sustained only light to moderate damage so yields may not be affected.
We are turning the page to start focusing on mid-season pests with a special interest in beginning to scout for kudzu bugs in seedling soybeans. Only a few have been spotted in Virginia. More on that as we progress. We are also expecting this to be a ‘stink bug’ year. Our generally warm wet spring and early summer conditions favor stink bug development. Our first indication that this may be the case is the large numbers of brown stink bugs being combined with wheat harvests. As they leave wheat fields, they will be hunting for other food sources moving through many crops including corn, soybean, cotton, tomatoes, etc., as the summer progresses. We are also gearing up for our brown marmorated stink bug soybean field survey. So far, only a few egg masses and nymphs have been reported from weed hosts. Soybeans will not be very attractive to them until plants start getting into the podding stages. More on that later.

Black light trap nightly averages for corn earworm moths were as follows: Chesapeake-0.3, Petersburg-0.3, Southampton-0.1, Suffolk-0.6. For brown marmorated stink bug, nightly averages were: Chesapeake, Southampton, Suffolk, and Virginia Beach-zero, Petersburg-0.3. Thanks to Watson Lawrence, Mark Kraemer, Chris Drake, Helene Doughty, and Ames Herbert’s crew for their reports this week.

There were zero corn earworm and brown marmorated stink bugs captured in black light traps this week for Prince George, Petersburg, Southampton, Chesapeake, and Suffolk. Thanks to Scott Reiter, Mark Kraemer, Chris Drake, Watson Lawrence, and Ames Herbert and his crew for this week’s reports. Other black light trap locations will be reporting soon, and we are trying to fix a possible electrical problem with the trap in Warsaw.

The cotton in our eleven research trials is in the 1st true leaf stage. We are rating these each week for injury (visual ratings) and numbers of adult and immature thrips (soapy water samples, 5 plants per plot). Numbers of immature thrips have more than doubled since last week, from a high of 40 immatures per 5 cotton seedlings last week to a high of 148 per 5 seedlings this week. These high counts are in the untreated plots and by comparison give us a good indication of how well the many treatments we are testing are working. Breaking it down a bit, the 148 count means that each 1st true leaf seeding has about 30 immatures feeding on the small bud. They must be standing in line to feed on the leaf cells. In general, the seedlings are still growing slowly so it is difficult to do accurate visual injury ratings—with only one true leaf to rate, just not enough plant material. So this week, we think the thrips counts give a better picture of how products are working, with the idea that by next week as plants push into the 2nd and 3rd leaf stages, treatment differences in levels of plant injury will begin to express.
Overall, foliar sprays alone (no seed treatment) of several products are providing some decent levels for control of immatures but not at the levels we think are needed to achieve cotton yield potential. We will provide more specific results soon, but one caution, as in the last few years, data show that we should avoid using pyrethroids. The treatments with the fewest number of immatures are the seed treatments followed by a foliar application. Several product combinations are working well. For example, in one trial the numbers of immatures in the better treatments range from 7 or less per 5 seedlings compared with 85 per 5 seedlings in the untreated control.
What are the recommendations? I think, based on the high numbers of immatures we are seeing this week, we may be at or near the peak. This is the best time to make that foliar application to minimize seedling injury. The results of that application will not be visible for 4-5 days, until the next leaf emerges, which should look normal, healthy, not crinkled or worse, blackened.
Peanuts are a different story. Over the last several years we have seen a trend where thrips numbers and injury to seedlings lags behind cotton by a week to 10 days. That is what we are seeing with untreated peanuts only showing the beginnings of the injury, at most a 3.5 on the 0-10 injury rating scale. This is compared to years when the injury can exceed 6 to 8 at the peak. Where cotton should be treated soon, peanut treatments could be delayed until the middle to end of next week.