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.

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

The kudzu bug situation has very quickly become a real problem for Virginia soybean producers. We are getting reports of infestations in the South Boston area and one from near Yale in Sussex County. I am quite sure that there are more infested fields. The image sent to me from the Yale field showed at least a dozen KB adults on a single plant. WHAT IS THE THRESHOLD and WHEN SHOULD YOU TREAT???
The treatment threshold for full grown R-stage plants has not changed (see below), but I have new information on thresholds for seedling/vegetative stage plants. Based on an experiment in GA, they (and others) are recommending treating at V2-V3 stage at an average of 5 bugs (adults and/or nymphs) per plant. The threshold increases to 10 bugs per plant for plants from 1-2 feet tall. The established threshold of one nymph per sweep (one swoosh of the net) should be used for plants above 2 feet tall. Plants should be sampled at least 50 feet from the edge of the field. The reason for this is that the adults have an extended migration period (6-8 weeks) and colonize field edges first. If you sample the edges, chances are you will make a spray decision too soon before the migration is over. They stress that these thresholds are PRELIMINARY and will absolutely change as we get more information.
Here is a ‘cautionary tale’ provided by Dr. Reisig at NCSU—“A NC grower noticed kudzu bugs on the edge of his April-planted beans in May 2012. They had not yet infested the interior portions of the field. He opted to spray. He then had to spray again in June, as the adults remigrated into the field. Additionally, sprays don’t kill eggs, so these hatched into nymphs. The grower then had to spray a 3rd time in June, as spider mites were flared in the field from the lack of beneficial insects. We want to avoid these costly situations while still preserving our yield.”
Off and running.

We are almost certainly going to have some problems with kudzu bug (KB) in soybean fields this summer. Why? We have been getting very early reports of adults from several southeastern counties for at the past several weeks (including Suffolk, Isle of Wight, Sussex, Dinwiddie, Greensville and Prince George). Likely they are much more wide spread. Adults are good fliers and land on clothing, vehicles, houses and other plants. Attached (hit the ‘more’ button) is an image just forwarded by Scott Reiter in Prince George County of adults that were found on a fig tree. Dr. Jeremy Greene (Entomologist, Clemson) shared that….”KBs can be numerous on fig trees. Although they are undoubtedly feeding to some extent, we do not think they are an issue on fig trees. We are recommending that they be sprayed with soapy water or insecticidal soap on these transient hosts in yards as they cause a nuisance. Dish washing detergent will kill or run them off.”
As you may recall, last summer in our Virginia soybean field surveillance program we observed adult KBs in soybean fields in 16 or so counties but not until well into the season. We reckoned that those adults had migrated from the south. A few nymphs were also found in a couple of locations. No fields became infested at treatable levels.
By contrast, this year’s very early adult activity means fields are at much greater risk. According to the folks in South Carolina and Georgia who have been working with kudzu bug since its first occurrence in soybean in 2009, this very early adult activity means a couple of significant things—one, the adults we are seeing now overwintered (in the adult stage) locally. This is a much different picture than what we had last summer and likely means we are at the beginning of having to manage them in fields. And two, they will begin to invade soybean fields as soon as they start flowering.
Most alarming is the report and image I just received (May 22) from Jim Oliver (Monsanto) that shows a volunteer soybean plant from the South Boston area covered with KB nymphs. This is the first record of a heavy nymphal infestation on soybean in Virginia. The nymphs are congregating on some of the 8-10 inch tall volunteer soybeans but not (yet) on the newly planted beans in that field that are about 3 inches tall. My advice was to wait to see if they move to the planted crop before making a control decision.
Fortunately, we do not have to ‘reinvent the wheel’ in terms of management recommendations—just stick with what has been developed in Georgia and South Carolina where they have had a couple of years of experience and research. First, infestations are most likely to be encountered in the earliest planted, full season, earliest maturity group soybean fields as those will be the first to flower. Second, the threshold is based on numbers of nymphs, NOT adult activity. Basically, we need to key on the nymphal stage of this insect in soybeans. Fields should be treated when the average reaches one nymph per sweep net sweep or if nymphs are easily found on stems, leaf petioles or leaves. Because there are only two complete generations per year, we should be able to control the nymphs for each generation and control population development. Third, there are several good insecticide options for controlling KB. We will provide more detail on these in future Advisories. These recommendations as well as good images of the different insect stages (egg, nymph, adult) are located in a kudzu bug field guide produced by Clemson University, University of Georgia and the United Soybean Board available online at: http://digital.turn-page.com/i/87846
Our advice, begin checking any soybean fields where plants have emerged, especially if you are located in the south central part of the state.
Additional information: kudzu-bug-adults-s-reiter-may-20-2013-jpg

Our final batch of corn earworm moths showed only 26% survivorship, down from last week. This season results showed a 37% survival rate for the seasonal total which exceeds all previous years. We are now up to 33 counties where brown marmorated stink bugs were/are present in soybean fields. Most are at pretty low levels compared with last year, but they are much more widespread. This week n some have been found in soybean fields in north central North Carolina. We are taking as much data as we can to help with answers for next season. And, the first kudzu bug nymphs were found in Charlotte County. We are nearing the end of this season in terms of insect pests and advisories…a long summer for sure.
Additional information: cew-cypermethrin-2011-2012-sept-13-2012-pptx

With our full complement of field scouts in place, more soybean fields are being found with BMSB infestations. We are up to 20 counties in Virginia (hit the ‘more’ button to see the map) spread over a very large area of the state. Infestations were a little slow to develop compared with last year but we are predicting that by the end of the season, many more fields will be infested compared with last year. So far, most infestations are at low to moderate levels (from 2-3 to 4-6 per 15 sweeps) but a few are in the high infestation range 8-10 or more/15 sweeps. We know that sweep netting is not the ideal way to sample for these insects, but there is no other method other than simply easing into the field edge and counting what you see. Basically, if you can stand in one spot, do a 360 degree turn and count more than 5 or 6, that area needs protection. So, how are they not ‘playing by the rules’? Last season, our first with treatable levels, bugs stayed on field edges and a single insecticide edge treatment provided season long control. This is true for many fields this year but in a few we are finding them deeper into fields, and, there are some cases where re-infestations are occurring in fields previously treated. The good news is that 1) based on our insecticide trials it is not difficult to kill them with several common products, and 2) many fields, especially the full season crop fields, are rapidly approaching the ‘safe stage’ which based on previous field cage studies happens after R6 (full seed) when pod walls begin to toughen. Many growers are treating field edges this year and we are going to follow as many as possible to determine if those treatments worked and held. More on this as we progress.
Additional information: herbert-bmsb-kb-va-aug-30-2012-pptx

Where much of the cotton crop is pretty much bug-safe, much of the Virginia soybean crop is in the most vulnerable growth stage, R5-early R6, to corn earworms and stink bugs. Both of these pests have a preference for the tender, developing seed (the R5 stage) and many fields are in or near that stage. The good news is that for the most part, corn earworm and native stink bug populations (green stink bug and brown stink bug) seem to be pretty light and spotty. Most reports are in the 1-3 worm/15 sweep range, certainly not excessive pressure, and the moth flight seems to be in decline. Native stink bug infestations are also very light to the point that and we cannot locate any field with a lot of native stink bugs. Although many growers have or are treating fields, if scouted, they are seeing that many fields are not at thresholds. We sometimes have another late summer/early fall corn earworm flight which could result in some new worm infestations, but it if this does happen, most fields will be in the bug-safe late R6-R7 stage.

A problem still exists with our adult pyrethroid vial test results. Last week’s sample reached 58% survivors, the highest level ever recorded for Virginia, and this week’s early sample was still at 50% survival. We have at least one report of lack of control in a soybean field treated with a pyrethroid (no need to mention any product names). If you are choosing a new product, a ‘brand’ you are not familiar with, be sure to check the label to see what you are buying/spraying. There are some products that are a mix of two pyrethroids (no help if you are concerned about pyrethroid resistance).

The problem story is with brown marmorated stink bugs. The more we look, the more we find. We are just now getting our scouts into the high risk counties in the northern and central areas. The reports show that many soybean fields in those counties (including Rockingham, Culpeper, Stafford, Madison and Orange Cos.) are infested at levels that need to be controlled. We do not have good thresholds or good sampling techniques for brown marmorated stink bug. It is almost impossible to get a good sample with a sweep net because they startle easily and drop to the ground quickly. But we do have data from last year that shows how damaging they can be to soybeans in the infested areas. The best we can offer now is that if you can visually ‘see’ several bugs on the upper leaves, there are MANY more down in the canopy feeding on seed. Like last year, field edge treatment seems to be all that is needed as the bugs are staying in the first 50 or so feet of the field edge. Edge treating (one spray boom width) was effective last year, and we are working to document the outcome (hopefully success) of this strategy again this year.

Kudzu bugs have not been reported in any new counties since our last pest advisory, but we do have reports of some egg masses in a couple of locations. We will likely see some nymphs soon in some fields, but time will tell if we get into any treatment situations. The later nymphs occur the lower the risk that they will develop into high populations, or that they will be able to cause any appreciable damage to plants. More next week as we progress with our scouting effort.

The attached 4-page pdf contains information on this year’s corn earworm moth vial tests, resistance management suggestions, links to Dr. Herbert’s corn earworm threshold calculator and his soybean chapter in the 2012 Virginia Cooperative Extension Pest Management Guide, a list of insecticides registered for use in soybean, and the results of Dr. Herbert’s 2011 corn earworm efficacy trials in soybean. Please click “More” to view this document. Additional information: resistance-mgmt-advisory-pdf

Dr. Herbert mentioned these items in his Aug. 8 advisory; here is the distribution map for kudzu bug (host crops = kudzu and/or soybean) and BMSB (host crop = soybean), attached as a pdf file. Thanks to the following scouts for their efforts: Ed Seymore, Jamie Hogue, Tami Carlow, and the Entomology Crew at the Tidewater AREC. Additional information: va-bmsb-kudzu-bug-2012-pdf