Tag Archives: insecticide

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

Application Equipment for Effective Insect Pests and Foliar Disease Control

Bobby Grisso, Ext. Agricultural Engineer and David Holshouser, Ext. Agronomist

Several years ago, we stressed that proper application equipment, specifically nozzle selection and spray volume, Fungicide Applicationwas critical to obtaining good disease control with foliar fungicides.  At that time, we were trying to prepare for an invasion of soybean rust.  The problem was that soybean rust (and most other diseases) would begin establishing itself in the middle and lower leaves of a full-canopied crop.  Getting enough spray droplets deep into the canopy was required for adequate control.

Although we have yet to see soybean rust early enough in the growing season and at great enough levels to cause a yield loss, we think our efforts to educate the agricultural community on proper application paid off.  Foliar fungicide sprays, now being used to control other soybean diseases, are reaching their target and penetrating to the middle and lower canopy.  Most importantly, it takes spray volumes of 15 to 20 gallons per acre (GPA) and medium-sized droplets to obtain good coverage.

Now we have another pest, the kudzu bug, which will likely require a similar spray strategy in order to get the pesticide down into the canopy where it needs to be.  Although this pest can be found on upper leaves and stems, past observations from states to our south indicate that it likes to bury itself well into the canopy on stems and lower leaves.  Therefore, revisiting nozzle and sprayer strategies for optimum control of this and other pests are warranted.

The single most important factor affecting prevention of disease and/or control of insect pests is good coverage of the plant with pesticide.  Fortunately, the technology is available.  You may however incur additional expenses with adaptation to current application equipment.

Remember the five major principles that result in satisfactory and economic control of the problem: 1) Positive identification of the insect pest or disease; 2) Correct pesticide; 3) Selection of the right equipment, particularly the right type and size of nozzle; 4) Timely application; and 5) making sure of the accuracy of equipment to confirm correct application amounts based on label recommendations.

First and probably most important, apply 15 to 20 gallons per acre of spray solution when using ground applicators.  Only with enough volume can we penetrate a large soybean canopy and cover the leaves with pesticide.  With aerial applications, this can be reduced to 5 gallons per acre (see the pesticide label for specific requirements).

Just as important, select the nozzles and pressures that will result in medium sized droplets (226 to 325 microns).  Pressure is not as important.  Depending on the nozzle selected, too high of pressure will just create fine and very fine droplets that are prone to drift.  Too low of pressure may create large droplets that may penetrate the canopy but not coat the leaves.Spray Droplet SizeFlat-fan pattern nozzles are still the best choice as long as most of the droplets from these nozzles are categorized as medium.  A flat-fan nozzle will normally be operated between 30 and 60 pounds per square inch (psi), with an ideal range of 30-40 psi.  Extended-range flat-fan nozzles are a modification of the flat fan that allows the applicator to spray at lower pressures and still maintain uniform distribution.  Regardless of the type of flat-fan nozzle selected, insure that the selected nozzle size will produce a medium-sized droplet at the operating pressure range and speed that the sprayer will be traveling.  Most nozzle catalogs will contain this information.  An example is shown below.Droplet Size Classification Chart - XRThe twin orifice flat-fan nozzle produces two spray patterns: one angled 30 degrees forward and the other directed 30 degrees backward.  Such a nozzle may provide better penetration and coverage of plants with fully developed canopies. This is mainly due to being able to double the gallons per acre while still maintaining the desired droplet size.  Still, hitting the target from two different angles, with one forward and one backward spray pattern may also provide a more effective coverage than spraying with just one spray pattern shooting down.  Twin orifice nozzles can be designed with a twin spray pattern from one tip or special fittings/caps that allow the producers to place two nozzles in the same cap, one pointed forward, and the other one pointed backward. Nozzles producing cone pattern are not recommended for foliar soybean diseases; droplets are usually too fine and will not penetrate the canopy.Nozzle PatternsHere are recommendations to help achieve the best coverage and control when spraying for soybean rust.

  • Keep spray volume above 15 gallons per acre for best results (20 gallons per acre is better).
  • Choose the appropriate size and type of nozzles and operate them at a pressure that will allow them to produce medium-size droplets (200-300 microns).
  • Nozzles producing a flat-fan pattern provide better coverage than the nozzles producing cone pattern when there is full canopy.
  • Use directed spraying, if applicable, to improve coverage.
  • Use twin nozzle/pattern technology. Two spray patterns, one angled forward and one angled backward, generally perform better than single nozzles spraying in one direction.  This is primarily due to being able to increase the spray volume, while maintaining medium-sized droplets.

For more information on sprayer technology, see the following VCE publications:

Nozzles: Selection and Sizing. Virginia Cooperative Extension publication 442-032, May 2013; http://pubs.ext.vt.edu/442/442-032/442-032.html (accessed: June 2013)

Droplet Chart/Selection Guide. Virginia Coopera­tive Extension, publication 442-031, May 2009; http://pubs.ext.vt.edu/442/442-031/442-031.html (accessed: June 2013)

Asian Soybean Rust – Frequently Asked Questions VI: Sprayer and Nozzle Technology.  Virginia Cooperative Extension publication 450-306, May 2009; http://pubs.ext.vt.edu/450/450-306/450-306.html (accessed June 2013)

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 (http://www.sripmc.org/Virginia).  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


Seed Treatments Have Their Place

Planting soybean into cool and wet soils is a recipe for more seedling disease problems.  Sometimes, you may never notice that there is a problem and, other times, certain areas of the field may be almost wiped out.  More commonly, the field in general is just not growing the way it should.

Some of our most noteworthy seeding diseases include: fusarium root rot, phytophthora rot, pythium damping-off and root rot, and rhizoctonia damping off and root rot.  Of these, fusarium and rhizoctonia are the most common in Virginia.  Some of these diseases can be managed with fungicide seed treatments, but some cannot.

Certain insect pests can also cause problems to seedling soybeans.  Thrips or leafhoppers can stunt growth when in high numbers on drought-stressed plants.  Bean leaf beetle seem to feed on young plants every year.  Both insects can transmit certain viruses.  Some companies are promoting insecticide seed treatments to help manage soybean aphid, but this is not relevant in Virginia.  Other soil insect problems include seed-corn maggot, wireworm, grub, and slugs.

Seed treatments are becoming more and more popular in all crops.  Benefits over soil treatments include lower use rates, less direct contact with toxic chemicals, and ease of use.  Fungicide seed treatments are sold under various brand names, but usually include one or more of the following active ingredients (with their most common trade names):  captan (Captan), thiram (Thiram), fludioxonil (Maxim), thiabendazole(TBZ), carboxin (Vitavax), PCNB (Rival), metalaxyl (Allegiance, Acceleron DX-309), mefenoxam (Apron XL), ipconazole (Racona), azoxystrobin (Dynasty), pyraclostrobin (Acceleron DX-109), or trifloxystrobin (Trilex).    Insecticide seed include the active ingredients:  thiamethoxam (Cruiser) and imidacloprid (Gaucho, Acceleron IX-409), and clothianidin (Poncho).

Finally, there is a new seed treatment (VOTiVO) that employs a biological mode of action with bacteria.  The product is being marketed in combination with clothianidin as Poncho/VOTiVO.  The bacteria lives and grows with young roots and supposedly creates a barrier against nematodes.  The verdict is still out with this product.  We have seen it increase yields in some nematode infested fields but not in others.  We will continue to evaluate this product.

In the near future, I’ll be exploring some of the disease and insect pests that could be causing early-season problems in soybeans.  We’ll start with an overview of individual pests and describe their potential damage.  Then later, we’ll talk about the potential benefits, if there are any, to applying one of the seed treatments currently available.

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.

Brown marmorated stink bugs found in high numbers in soybean fields (Dr. Ames Herbert)

Thanks to the conscientious effort of our field scout, Ed Seymore, we have located several soybean fields in Orange County, Virginia (about 20 miles NE of Charlottesville) with large numbers of brown marmorated stink bugs. These high density areas are very much restricted to field edges next to woods, especially where there are groups of tree or heaven. On these field edges we could easily capture 10 to 20 adults and nymphs, or more, in a 15-sweep sample. The ratio of adults to nymphs was heavy on the nymph side, with evidence of old egg masses on the leaves. As best we could determine these infestations went only about 30 feet into the fields, then numbers dropped to 1 to 2, or less per 15 sweeps. There was evidence of feeding with flattened pods and discolored pods with damaged seed. There is no question that these infested areas will suffer from stay green syndrome at the end of the season. We are not sure how widespread this problem is, but are doing what we can to locate other problem areas/fields. So far, we have no other reports. In one field, we were able to put in a couple of fairly primitive insecticide efficacy trials. I use the word primitive because we had to fit plot plans into these narrow field edges with their curves and ups-and-downs (not much flat ground in that part of the state). We hope to take post treatment ratings soon and will post results, if we are successful.