Category Archives: Insect

Kudzu bug is rapidly becoming a major challenge in the Virginia soybean crop

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At this point, we have officially entered a new phase in the kudzu bug saga with at least two fields known to have very high numbers—one each in Isle of Wight and Culpeper Counties—and both need to be treated with insecticide. Most of the infestations seem to be confined to field edges or corners of fields. That being the case, we are recommending spot treatments—knowing that some fields are small enough that whole field treatment makes more sense.

In general on the statewide level, kudzu bugs have cycled through the overwintering adult stage, have laid egg masses, and nymphs have hatched—at least this appears to be the case in the fields we have visited. We think the few adults we are seeing are second generation adults that will set up another cycle of nymphs.

We are relying on thresholds ‘imported’ from the researchers in the south. I am most concerned about fields in the flowering or pod development stages and the threshold for those fields is an average of one nymph per sweep (15/15 sweeps). Again, we are now seeing a limited number of fields at or above threshold but I anticipate that 1) there are likely a lot more at threshold but not indentified since many fields are not being checked, and 2) many more fields are going to hit threshold before the season is completed.

We are trying to stay abreast of this situation and will keep updating our advisories.

Corn earworm (CEW) update and pyrethroid vial testing results, to date

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CEW activity is low compared to this time in previous years. We have not captured many moths in our pheromone traps and even fewer in black light traps. We know that CEW populations are usually low in generally wet years, which is what we are experiencing this year, so the pattern seems to fit. This can change—quickly, depending on weather patterns.

We are initiating our annual field corn survey to document the infestation level, which will help predict the infestation level growers can expect in subsequent crops. Many VCE Ag Agents across much of eastern/central Virginia are cooperating on this survey and we hope to have it completed by the end of July.

The situation with pyrethroid sensitivity is developing quickly. To date we have tested 188 moths with the AVT (adult vial test) pyrethroid challenge with an overall survival rate of about 17%. This is a relatively high level for this early in the season. How will this progress? Time will tell.

Generally low levels of insect/mite pressure in peanut

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Compared to past years, we seem to be in a low cycle for many peanut pests. For example, not so many years ago it was pretty common to see rampant twospotted spider mite infestations turning large areas of peanut fields yellow, then brown. Dr. Rick Brandenburg at NCSU and I spent a lot of time in those years developing what at the time was the most effective management strategy: first miticide application at early detection followed by a second in 5-7 days. It took this two-spray system to break the mite egg-laying cycle and stop the infestation. Where have the mites gone? We see a few in fields every year but even in dry years we just do not encounter many really bad infestations. Let’s hope this holds because if we do start having problems, we have almost no control products available. The two general rule-of-thumb practices to lower risk to spider mites are 1) to use insecticides sparingly and only as needed, and 2) prevent mowing or burn down of weedy field edges during the high risk months of July and August.

Another pest that seems to be in a slack phase is the potato leafhopper. You can certainly find hoppers and some evidence of hopper burn in a lot of fields but it is pretty rare to see fields that are badly injured. During the heavy infestation years we ramped up field trials and were able to develop a decent plant injury threshold based on the relationship of percent of leaves showing hopper burn and pod yield. Results showed that yields began to be affected (reduced) when injury exceeded 20-25 percent of leaves. That is, some hopper burn is tolerable and will not cause any yield reduction, but there is turning point. Where are the badly injured hopper fields? Not easy to find these days and hopefully that will not change. Scout fields in July and August and tank mix an insecticide with a leafspot spray, but ONLY if plants are approaching the injury threshold and hoppers are active.

Southern corn rootworm (SCR) has received a lot of attention this summer because of the overall wet conditions that favor this soil pest. Many comments relating to SCR management were recently posted by Dr. Brandenburg and we are on the ‘same page’ so no need to restate. I do have a couple of additional observations. Even in recent moderately wet years we have not been seeing or hearing of much rootworm injury. And in general, we are not seeing as many of the adult cucumber beetles flying in and around peanut fields as we used to. During years with more consistent pressure, Dr. Brandenburg and I did a lot of work to establish the Southern Corn Rootworm Risk Index as a system to determine which fields are at risk. In normal rainfall years, it’s a pretty effective management system. Although we see some variability in its effectiveness, chlorpyrifos (Losrban) is still the only insecticide available if control is needed.

Corn earworm infestation intensity also varies from year to year with the general pattern of being worse in overall dry years and less of a problem in wet years. In my opinion however, corn earworm is only worth mentioning because many people spray for it, even though it is not an economic problem in peanuts. In the 25 years I have been working with the peanut crop, I can recall only ONE case where enough plant material was consumed by worms to result in a yield reduction—and that was in a dry year when the peanut plants had not developed a large canopy. In most years when worms move into fields with full-canopy, knee-high plants, they cannot eat enough leaf tissue to be a threat.

In summary, in general we seem to be in a ‘quiet’ period for peanut insect/mite pests. Pressure by mites, hoppers and rootworms has been generally low in recent years and so far, we have not experienced the burrowing bug or three-cornered alfalfa hopper problems that plague some Georgia and South Carolina growers. We have also been lucky with lesser cornstalk borers. Of course this could all change—in one year. So, feel lucky—but stay vigilant and question the need for each and every insecticide spray.

Black light trap counts for week ending July 18, 2013

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Nightly averages for corn earworm moths captured in area black light traps for this week ranged from zero to 7.7; brown marmorated stink bugs ranged from zero to 13.5 per night. Please click “More” for the summary tables for these two pests. Thanks to our trap operators John Allison, Watson Lawrence, Mark Kraemer, Scott Reiter, Ames Herbert and crew, Helene Doughty, and Jim Jenrette for their reports this week. Additional information: 18-jul-cew-bmsb-pdf

CEW/BMSB black light trap counts for week ending July 11, 2013

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This week’s corn earworm and brown marmorated stink bug black light trap counts are included in the attached table (a pdf document; please click the More button). Thanks to trap operators John Allison, Watson Lawrence, Mary Beahm, Mark Kraemer, Scott Reiter, Helene Doughty, Jim Jenrette, and Ames Herbert and the Tidewater AREC entomology crew for their reports this week. Additional information: cew-bmsb-7-11-13-pdf

Black light trap catches for the week ending July 3, 2013

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Average nightly black light trap catches for corn earworm moths were: Petersburg = 2.0/night; Warsaw = zero; New Kent = 4.3; Charles City = 4.7; Suffolk = 0.5; Painter = 0.9; Virginia Beach = zero. Brown marmorated stink bug nightly trap catch means were: Petersburg = 0.7; Warsaw = 0.2; New Kent = 0.6; Charles City = zero; Suffolk = zero; Painter = zero; Virginia Beach = 0.7. Thanks to our trap operators Mark Kraemer, Mary Beahm, John Allison, Ames Herbert, Jim Jenrette, and Helene Doughty for their reports this short week.

Kudzu bug update

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As of this week (June 27, 2013), we have documented kudzu bug (KB) infestations in soybean fields in 20 counties. The problem is spreading quickly and almost daily I get word of an infestation in another county. For the sake of record, I will list them at the end of this advisory so if you find KBs in a soybean field in a county that is NOT on the list, please contact me with that information. If you are growing soybeans (or crop advising) in a county on the list, you should make the effort to check fields.

Although adults are still present, nymphs are hatching from eggs masses and dispersing to stems and petioles. Adult KBs have a strong aggregation pheromone that results in clusters on individual plants with many plants not infested. This will begin to change as nymphs emerge. Their tendency is to disperse to new feeding sites, new plants or areas of plants which will result in a more widespread and more uniform infestation. As of this week, the nymphs we are seeing are quite small. You can see them with your naked eye, but it takes either really good vision (those days are over for me) or a hand lens to see that those tiny light colored things on stems are indeed KB nymphs. This too will change as they gradually grow and molt into larger nymphal instars.

Based on all that we know, we should try to keep the management recommendations as simple as possible, trusting those that have done the research—that using their recommendations will result in the best possible outcome: control at the least cost. As we move forward in the season, the best advice is to treat fields that are flowering or developing pods when an average of one nymph (big enough to see) is capture per sweep net sweep—or, 15 nymphs in a 15-sweep sample. If this situation is encountered, we are advised to treat that field. Remember, this insect is a slow feeder—gradually drawing down a plant’s vigor. This is good in a way, as this gives us plenty of time to sample fields and react with a treatment if needed. KBs do not eat holes in leaves and do not take bites from pods or seed. You may find nymphs and second generation adults on pods, but the damage is not direct like a corn earworm that eats the seed or a stink bug that punctures the seed.

This is a new pest for us and we will all have to learn how best to deal with it. For now, we should abide by the recommendations above. Given the number of infested fields, I fully expect that some will have to be treated, eventually.

What about product choice. We have covered this in an earlier advisory. There are many good choices. The attached insecticide efficacy chart (hit the ‘more’ button) was developed by researchers at Clemson University and University of Georgia. They (and I) do not recommend using any product that falls below 80% control, and the higher the better. I have been asked about a lot of products, some on this chart, some not. I go with the chart.

Accomack
Amelia
Brunswick
Sussex
VA Beach
Franklin (Co.)
Appomattox
Greensville
Suffolk
Charles City
New Kent
Southampton
Dinwiddie
Prince George
Culpeper
Orange
Campbell
Middlesex
Isle of Wight
Goochland
Additional information: kudzu-bug-efficacy-chart-2013-pptx

Black light trap report for week ending June 27, 2013

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After several inquiries about whether kudzu bugs can be monitored using black light traps, Dr. Herbert and I have not heard that kudzu bugs come to these traps. The average nightly corn earworm moth catches from black light traps were: Petersburg = 0.4 per night; Suffolk = 0.1; Virginia Beach (Hampton Roads AREC) = 0.1; Charles City = 6.3; King William = 0.2; New Kent = 2.4; and Warsaw (Eastern Virginia AREC) = 0.4. The average nightly number of brown marmorated stink bugs were: Petersburg = 2.9; Suffolk = 0; Virginia Beach (Hampton Roads AREC) = 0.1; Charles City = 0; King William = 1.3; New Kent = 0.1; and Warsaw (Eastern Virginia AREC) = 0. Thanks to our trap operators Mark Kraemer, Ames Herbert and his entomology crew, Helene Doughty, John Allison, Laura Maxey, and Mary Beahm for their reports this week!

Black light trap catches for week ending June 20, 2013

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Low numbers of corn earworm moths were reported this week from black light trap operators. Nightly averages were: Southampton = 0.3 (from C. Drake); Warsaw = 0.5 (M. Beahm); Petersburg = 1.3 (M. Kraemer); Suffolk = 0.1 (A. Herbert). Brown marmorated stink bugs were only found at the Petersburg trap (2.3 per night) [M. Kraemer], but they were captured in a Virginia Beach black light trap earlier this month (1.3 per night for June 7-13) [provided by H. Doughty]. Thanks to the above-mentioned trap operators for their reports this week.