Category Archives: Insect Pests

Brown Marmorated Stinkbug and Kudzu Bug Update

Both the brown marmorated stinkbug and kudzu bug continue to expand their territories.  Below is the latest update of this expansion.Kudzu Bug 080913

BMSB 080913A few fields have needed treatment.  We’ve been successful with edge of field treatments with the brown marmorated stinkbug, as they tend not to move into the middle of the fields.  Hopefully, this IPM strategy will continue to remain effective.

For the kudzu bug, the threshold is 1 kudzu bug nymph per sweep.  So, to trigger a spray, you’ll need to average 15 nymphs per 15 sweep sample.  Also keep in mind that insecticides vary in their effectiveness.  See the chart below for the most effective products.  Products highlighted in pink are recommended.
Kudzu insecticides

Corn Earworm Survey—2013

D. Ames Herbert, Jr.
Extension Entomologist
Virginia Tech Tidewater AREC

Annually, we conduct a survey to estimate Helicoverpa zea (corn earworm) infestation levels in field corn in mid- to late July. Corn is considered a nursery crop for earworm, allowing the pest to complete a lifecycle and then move on to other crops such as soybean, cotton, and peanut in August. Over 30 years of data show that there is a linear correlation between the infestation level in corn and the amount of soybean acreage that gets treated with insecticide for this pest.

To conduct the survey this year, the number of corn earworms found in 50 ears of corn was recorded in 5 corn fields in each of 27 counties, totaling 6,750 ears and 135 fields sampled. When fields were known to contain Bt or non-Bt corn, this was noted. Otherwise, samples were considered to be random and assumed to be representative of the actual Bt/non-Bt composition in each county. Age of earworms, or if they had already exited the ears, was also recorded (data not shown). We greatly appreciate the help of Virginia Cooperative Extension Agriculture and Natural Resource (ANR) Agents, Virginia Tech faculty and staff, and volunteers in this effort. These cooperators are acknowledged below. We also would like to thank the many growers who graciously allowed us to inspect their fields for earworm.

Results of the survey can be found at the Virginia AG Pest Advisory ( Statewide, approximately 18% of ears were infested with earworms. For comparison, 30% of ears were infested in 2012, 33% of ears were infested in 2011; 40% in 2010; and 36% in 2009. Regional averages for 2013 were 9.2% infested ears in the Northern Neck, 15.1% in Mid-Eastern, 15.7% in South-Central, and 23.4% in the Southeast.

This survey is intended to be a representative sample, not a complete picture. We always recommend scouting individual fields to determine exactly what is happening in terms of corn earworm as well as other pests and crop problems. Also, please check the black light trap data on the Virginia Ag Pest Advisory and other reports posted weekly to keep up-to-date on the insect pest situation.

Kudzu Bug Update

Ames Herbert, Extension Entomologist

The map below lists the progression of kudzu bug in Virginia from 2011 and 2012 (blue and orange counties) though this year (purple counties).  Kudzu bug adultAs of June 27, 2013, we have documented kudzu bug (KB) infestations in soybean fields in 21 of those counties (Accomack, Amelia, Appomattox, Brunswick, Campbell, Charles City, Culpeper, Dinwiddie, Franklin, Greensville, Goochland, Hanover, Isle of Wight, Middlesex, New Kent, Orange, Prince George, Southampton, Suffolk, Sussex, and VA Beach).  The problem is spreading quickly and almost daily I get word of an infestation in another county.  If you find KBs in a soybean field in a county that is NOT listed, 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.Kudzu bug distribution map 070113 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.Kudzu bug nymphs-first instar

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 the last week in June, 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.Kudzu bug egg to adult 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, see image below)Kudzu bug nymphs is captured 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.  Below is an insecticide efficacy chart that 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.Kudzu bug insecticides list


Kudzu bugs now found infesting soybean fields in Virginia

Ames Herbert, Extension Entomologist
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. Kudzu Bug 2Plants 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.

Corn earworm AVT results, BMSB and Kudzu bug update….nearing the end (Dr. Ames Herbert)

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.

Brown Marmorated Stink Bugs Infesting Soybean Fields – Not Playing By the Rules (Ames Herbert, Extension Entomologist)

With our full complement of field scouts in place, more soybean fields are being found with brown marmorated stink bug (BMSB) infestations. We are up to 20 counties in Virginia 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.

This report was taken directed from Dr. Herbert’s Weekly Virginia AG Pest Advisory.  To access this advisory, go to


Corn earworm moths already showing high levels of pyrethroid resistance in Virginia

From Ames Herbert via the Virginia Pest Advisory (

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)

Early-Season Insect Pests

Potato Leafhopper. This insect overwinters in gulf-coast states and migrates northward each year, typically arriving in Virginia between late April and early June. Adults and nymphs injure the plant by inserting their piercing-sucking mouthparts into plant tissue and removing liquids. High populations can result in visual injury (cupping of leaves) and under drought conditions, can stunt growth, Injury is more severe on varieties with little leaf pubescence. But, the injury will not necessarily result in yield loss. Very dry conditions will increase injury and likelihood of yield loss. The insect can be controlled with pyrethroid insecticides.

Thrips may be the most abundant insect pest species on soybean.   But, the feeding alone will not usually cause yield reduction.  Under favorable environments, soybean will outgrow thrips damage.  However, if high numbers of thrips coincide with droughty conditions early in the season (seedling plants), then growth can be severely stunted and yield loss might occur.  Thrips feed by rupturing the cell walls of leaf cells and sucking the exudates.  Leaves will take on a silvery appearance from thrips feeding.  The insect can be controlled with insecticides from several chemical classes.  Early-season control can be obtained with insecticide seed treatments.  Ames Herbert is updating thrips counts in cotton and other crops on a regular basis in his Virginia AG Pest Advisory found at

Bean leaf beetle is a common pest through all soybean production areas and has become more of a concern in the Midwest in recent years.  These beetles are defoliating insects, whose injury is easily recognized by small round holds between major leaflet veins.  The insect can also feed on the surface of soybean pods, leaving the seed vulnerable to excess moisture and secondary pathogens.  The insect can feed all year, but most concern is during the early vegetative stages.  However, soybean can normally grow out of this injury, without yield loss.  This insect can transmit the virus, bean pod mottle virus.  However, viruses have not traditionally been a problem in soybean.  There is resistance and/or tolerance in many varieties.  However, we suspect that some newer varieties have less tolerance.  The insect can be controlled with insecticides from several chemical classes.

Soybean Aphid.  Soybean aphid is a relatively new pest, first discovered in Virginia just 10 years ago.  It feeds by sucking plant sap, which can cause leaf curling and plant stunting and pod abortion.  At high levels, yield can be seriously reduced.  While an early-season pest in the Great Lake states, it has never occurred in Virginia before July, and rarely before August.  In addition, it only reaches threshold levels on relatively few acres in Virginia each year.  We only mention this pest here because some companies are promoting early-season control of aphid with soil insecticides.  Although soil insecticides may provide some control to seedling soybeans, this is not an issue in Virginia.  Management of this pest depends on regular scouting and applying insecticides when threshold levels are reached (250 aphids/plant before R5).

White Grubs.  With less tillage and more residue buildup on our soils, grubs have become more of a concern.  White grub damages soybean by feeding on soybean roots, killing young plants, and reducing stands.  Insecticide seed treatments have some, but limited effect on grub.

Wireworms.  As the name implies, wireworms are wire-like worms that feed on soybean seed, preventing germination.  This leads to poor and spotty stands when populations are high.  They may also feed on the underground base of the plant.  Later, they may feed on roots.  To determine if wireworms are a problem, bait stations can be employed.  Seed treatments are effective against wireworm.

Lesser cornstalk borer can be a problem on seedling soybean; problems on older soybean are infrequent.  Outbreaks are more likely under hot, dry conditions and in sandy fields with weedy hosts.  Larvae of this insect bore into the main stem at or just below the soil surface.  Numerous seedlings can be injured by a single larva.  Seedlings can be cut off at the soil surface or the tunneling can cause wilting and death.  Surviving plants may lodge and be lower yielding.  Insecticide seed treatments or other applications are not effective.

Insecticide seed treatment to soybean is of limited value in Virginia.  Seed treatments can reduce feeding by some species of insects early on the season, for the first 3 to 4 weeks after plant germination.  However, we do not typically treat for insects early, nor is there data to support the value or need.  Early season insects include thrips (various species) and bean leaf beetle.  Ames Herbert, Extension Entomologist, spent several years doing tests across the state trying to determine the value of treating for thrips and was never able to find a yield advantage.  Bean leaf beetle can feed on seedling plant leaves, but he has never seen a yield reduction from the feeding.  In the north central US, growers use seed treatments to reduce first generation soybean aphid.  In Virginia, we do not see aphids until late July or August long after any seed treatment would be out of the plant system.  Seed treatments may have some utility for wireworms and grubs.

Kudzu Bug.  Although not necessarily an early-season insect, this new pest is showing up early this year just to our south.  Little is known about this insect, but we are learning quickly.  This insect was discovered in Georgia in 2009, moved into South Carolina in 2010 and through North Carolina in 2011.  It was also found in Patrick County, Virginia in 2011.  As of May 2012, it has already been found in at least six N.C. counties and in Greensville County, VA.  It feeds on wide range of legume hosts including kudzu, wisteria, some vetches, and soybean.  It has several generations per year, moving from sheltered areas such as bark or rocks in the winter to kudzu and then on to soybeans.  Like an aphid, it has piercinig and sucking mouthparts, therefore does its damage by sucking juices and nutrients from the plant.  Of the studies conducted in 2010 and 2011, it has reduced soybean yield by an average of 21%.  We need to track this insect, so timely spray recommendations can be implemented.  So if you see this insect, please notify your County Extension office or you can contact Ames Herbert directly at the Tidewater AREC.  You will be hearing more about this insect, so stayed tuned.

Late Season Onslaught of Corn Earworm (Dr. Ames Herbert)

It may be happening for the first time that I can recall a late season infestation of corn earworms in soybeans. The last couple of nights we have trapped more corn earworm moths (about 1800 and 1500, respectively) in our pheromone traps than we have ever captured. These are alarmingly high numbers and I am getting reports that folks are seeing a lot of moth activity in and around fields of cotton, soybean and peanut. I got the first report today that some growers in southern Southampton County are having to retreat some soybean fields. I have been telling folks that as best I can remember, I have never seen a new infestation of earworms develop in September. Well, as one of my earlier mentors said to me one day. Dont make predictions about insects. Theyll make a liar out of you every time. Seems he was right. So, what crops are at risk? The cotton and peanut crops are safe as we are close to defoliation time with cotton and digging time with peanuts. Only late planted soybean fields that still have susceptible pods (earlier than R7 growth stage) are at risk. The good news is that our corn earworm pyrethroid vial test results have been showing a gradual decrease in the percent of moths surviving (see the attached graph) to levels below 10%, which means that pyrethroid insecticides should provide good control, relatively inexpensively. If I was someones mentor, I would want to go down in history as saying, Never let your guard down. Never stop checking fields for insect pests until the crop is mature

Brown marmorated stink bug in soybean, summary to date (Dr. Ames Herbert)

The brown marmorated stink bug (BMSB) which was first identified in 2001 in Allentown, PA, is now infesting soybean fields in parts of Virginia. This stink bug, although similar in appearance to our native brown-colored species, can be easily distinguished by the white bands on their antennae, and the white bands on the legs of nymphs. BMSB is a known pest of many crops, wreaking havoc on fruit crops, wine grapes and many vegetable crops, especially sweet corn. Although the epicenter for this pest is still the mid-Atlantic region (PA, DE, MD, VA and WV), a few have been found in states as distant as California. BMSB, like our native stink bug species, feeds directly on developing soybean pods and seed. If the damage occurs very early in seed development, pods will be flat and brown, but still be attached to the plant and easy to see. If damage occurs later in seed development, pods will appear yellow and speckled, and opening the pod will reveal damaged, crinkled, stained seed. Last summer (2010) we began a monitoring program for BMSB in soybean and found them in soybean fields in 15 Virginia counties, but always in low numbers. In Maryland where they had seen these same kinds of low numbers the previous year (2009), last summer (2010) they found large infestations on field edges. The same pattern has occurred for us. This summer (2011) we have found several fields with very high numbers. So far, the heavily infested fields are confined to one geographical areathe north-central piedmont counties of Orange, Culpeper, Madison, Fauquier and Clarke. Very low numbers have been reported in other counties. A pattern seems to be emerging that is playing well for us in terms of managing BMSB in soybean. To date, yield threatening infestations seem to be confined to field edges, not going beyond 30 to 50 feet into the field. Heavy infestations also seem to be associated with fields with wooded borders, especially if there are concentrations of the invasive weed, Tree-of-Heaven (Ailanthus altissima). Both BMSB and Tree-of Heaven are native to China and other parts of Asia. BMSB seems to be strongly attracted to that host, especially when the trees are putting out their seed clusters. Not coincidently, the north-central piedmont area where we are finding the highest densities of BMSB in soybean is the area with the highest concentration of Tree-of-Heaven. I encourage you to Google Tree-of-Heaven and become familiar with what it looks like. This strong field edge effect has made it possible for our local soybean growers to make edge treatments applying insecticides in one spray-boom width around a field, without having to treat the entire field. We are revisiting as many of these edge treated fields as often as we can, and so far, the edge treatments are holding. Another bit of good news is that many of the insecticides commonly used in soybean are effective against BMSB. This summer, we were able to put out three insecticide trials in growers fields in Orange County and most of the products we applied worked very well (including Baythroid XL, Belay, Brigade, Cobalt Advanced, Endigo ZC, Lannate LV, Orthene 97, and Vydate L). The problem for fruit growers is not that they cannot kill these critters, it is that they continue to reinvade their orchard which necessitates repeated sprays. Will this also occur in soybean fields? We are not certain. How should growers react to this new pest? We are recommending that growers stay vigilant until the latest planted fields reach the R7 growth stage when beans would no longer be susceptible to stink bug feeding. Scout field edges, especially fields with wooded edges with clusters of Tree-of-Heaven. Use a sweep net to sample the plants by making successive 15-sweep samples. We have no exact threshold, but suggest that greater than an average of 4 adults or nymphs per 15-sweeps would constitute a risk to the pods and seed. We have encountered fields with 8 to 10 per 15 sweeps, and in some extreme cases, more than 20 to 30 per 15 sweeps. So, the bad news is we have another established insect pest of soybean in Virginia. The good news is we have already made some progress in terms of how best to manage it. As a final note, we are also in the process of doing field cage studies to determine 1) how damage by BMSB may differ from damage by our native stink bug species, and 2) what a damage threshold might be more on this later.