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.

percentages—implications for treatments in soybean
At the time of this report, we have tested 109 corn earworm moths this week. These moths represent the ‘front edge’ of the large second generation flight from corn. The results are not good. The first batch of 49 moths had 49% survivorship and the second batch of 60 moths had 53% survivorship. We have another 150 moths in vials to be assessed tomorrow (Friday). What does this mean? This confirms what I thought we might see based on previous year’s patterns—with survivorship percentages peaking in late July/early August. If corn earworm flights are heavy and large worm infestations set up in soybean fields, non-pyrethroids will need to be tank-mixed with pyrethroids (which are still recommended to control whatever stink bugs may be present). We have had success with several pyrethroid tank mix options including with Belt, Steward, and Orthene. I was asked about Lannate. Lannate is an effective product against corn earworm but I have not tested whether it will tank mix with a pyrethroid. If you choose this option, you should jar-test the mix before loading your spray tank. Also, although effective, Lannate has a very short residual activity period—24 hours, unless it rains. If the worm infestations do not develop to high levels, the pyrethroids will probably still do a decent job—apply them only at the highest labeled rate.

Below is an advisory provided by Bill Shockley, Virginia Coop. Extension Ag Agent in Northampton County (southern most county on the Del-Mar-Va Peninsula). This is a traditional vegetable and potato growing county so insect pests are often different from what we find on the ‘mainland’. But Bill’s comments are insightful. And, we also have reports of some beet armyworm infestations in Virginia Beach soybean fields

From Bill Shockley: We are finding a large number of beet armyworms in young soybeans in Northampton County, Virginia. They are especially prevalent in soybean fields planted double crop after potatoes, string beans and other spring planted vegetable crops. These insects are foliage feeders and will severely damage leaves and stems of young soybean, lima bean and string beans plants. Traditional spray applications of pyrethroid insecticides have been generally ineffective in the past for controlling these pests. Labeled applications of Steward, Belt or Lannate have provided the only significant control of these insects.

We are also beginning to find generally low numbers of corn earworms in soybeans in some areas. As soybeans begin to blossom, and pod formation begins, these insects will become more of an economic problem in this crop.

It is vitally important to begin scouting for these insects at this time. The timing of chemical control applications for these pests is very important to assure maximum control and limit unnecessary production costs.

We are getting a few calls about spider mites in soybean. Following is an update from Dr. Joanne Whalen at University of Delaware that covers management and control. This is a very well done summary that addresses a lot of the issues regarding product choices, their strengths and weaknesses and other very valuable information.

Dr. Whalen: With the extended drought conditions in our area, we continue to find significant populations of spider mites in both full season and double crop fields as well as in irrigated fields. In most cases infestations are field wide so edge treatments will not be effective. As we learned in past years, drought will seriously stress plant growth, favor mite development and create plant growth conditions that make it difficult to achieve effective control. Early detection, rotation among available control options and multiple applications are often needed under drought stress conditions. Under high population pressure, a single treatment is often not adequate to kill all the life stages. Mite eggs will not be affected by the initial knockdown/control of adults and nymphs and thus hatch after a few days. The only available materials for spider mite management in soybeans in Delaware are dimethoate, Lorsban (as well as generic chlorpyrifos products), bifenthrin (numerous generics available) and Hero. (Be sure to read all labels before spraying for restrictions and rates). Unfortunately, we do not have a selective miticide labeled for soybeans like we do in vegetable and fruit crops. The following is a summary of what we have seen so far this season as well as a summary of results from past seasons.

Hero and bifenthrin Products – A number of products containing the active ingredient bifenthrin are available for spider mite management in soybeans . Some examples include Brigade, Bifenture, Frenzy and Sniper. In addition, Hero, a combination product including both bifenthrin and zeta-cypermethrin (two pyrethroids) is also available. In many cases, these materials have provided good initial control but a second treatment has been needed, especially if populations were exploded at the time of treatment and numerous mite eggs were present. Early detection and control is needed as with all of the materials available for mite management in soybeans. In addition, most of the labels for products containing bifenthrin state “: “do not make applications less than 30 days apart or do not apply more than once every 30 days“. Therefore, you will need to rotate to a material with a different mode of action if a second application is needed.
Dimethoate – In past years, dimethoate has not provided effective spider mite management under drought stress conditions. However, this year we have received reports of fairly good control in some situations but it should be noted that rain was received in those areas. Although dimethoate is the only systemic material available for spider mite management in soybeans it must be absorbed and translocated by the leaf tissues to provide residual action; otherwise, it undergoes rapid photodecomposition from sunlight. This leaf absorption process is greatly reduced in drought-stressed plants that have “shut-down” physiologically. Another important factor that plays a role in the performance of dimethoate is the pH of the water used as the carrier. Many pesticides, especially dimethoate, are subject to breakdown by alkaline hydrolysis. (http://www.ag.ndsu.nodak.edu/aginfo/entomology/entupdates/ICG_08/01_Intro_08.pdf) In alkaline water (high pH), there is a break in certain bonds in the dimethoate molecule, causing two or more new molecules to form. This increases the decomposition rate of the insecticide and can result in poorer than expected field performance. Dimethoate degradation is also accelerated by the mineral content of the water, especially the presence of iron. If a high pH situation exists, you can lower the alkalinity of the water in the spray tank by adding an acid-based buffer. An important consideration is to select a buffering product that lowers the pH to the acid range without causing phytotoxicity. Also, the buffer must be added to the spray tank first, before the addition of dimethoate.
Note – the dimethoate label states it has a “ 7 day reapplication interval. “
Lorsban (chlorpyrifos)- We have seen good initial control of mites with Lorsban and other generic chlorpyrifos products this season. A second application with another material has been needed especially if populations were exploded at the time of treatment and numerous mite eggs were present. Lorsban ( and other generic chlorpyrifos products) can provide good contact control of motile mites when applied in enough water to get good coverage. Since Lorsban is not a systemic product, a second spray of non-chlorpyrifos product may be needed in 5 to 7 days to kill newly hatched mites. The Lorsban label states that: (1) When large numbers of eggs are present, scout the treated area in 3-5 days and if newly hatched nymphs are present, make a follow up application with a non-chlorpyrifos product and (2) do not make a second application of Lorsban 4E or other product containing chlorpyrifos within 14 days of the first application. So before applying any material, be sure to read the label for rates as well as all restrictions including but not limited to the total number of applications allowed, rotation between materials, minimum number of days required between applications as well as the pre-harvest interval between last application and harvest. Spider mite management is never easy under drought stress conditions. Early detection and multiple applications of materials with different modes of action are often needed to reducing losses from this pest in soybeans. As a reminder, under heavy mite pressure and extended hot, dry weather, it often takes an extended period of free moisture on leaves, high humidity during the day and cool evening temperatures to get an increase in the fungal pathogens that can significantly reduce exploded mite populations.