Category Archives: Soybean

Soybean Rust Update: September 19, 2013

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Since the announcement that Asian soybean rust (SBR) was found in the sentinel plots at the Tidewater AREC, we have been receiving lots of inquires about what the risk is to the soybean crop and whether or not it is prudent to spray. Attached I have provided a somewhat lengthy description of the status of SBR in Virginia and the factors growers should consider before deciding whether or not to spray. Please contact me if you have any additional questions or concerns regarding the status of soybean rust in Virginia (Hillary Mehl, Extension Plant Pathologist: hlmehl@vt.edu). Additional information: virginia-soybean-rust-update-9-19-13-pdf

Soybean Rust found in Suffolk, VA

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On September 17, 2013 soybean (SBR) rust was observed and confirmed on soybean leaves (10/34 leaflets, 2% leaf coverage) collected from one of the Tidewater AREC sentinel plots on September 5. Suffolk is the only county in Virginia thus far with confirmed soybean rust, but we will now intensify our scouting efforts throughout the soybean-growing regions of the state.

So far in 2013, SBR has been confirmed on soybeans in 185 counties/parishes in 10 states in the U.S. (AL, GA, FL, MS, LA, SC, AR, NC, TN, and VA) including two counties in North Carolina and one county in SE Virginia.

Soybean sentinel plots and commercial fields are monitored annually for early detection of SBR and tracking of disease spread. Data are used to make recommendations for timely applications of fungicide sprays for control of SBR. Since August, soybean leaflets from sentinel plots at the Virginia Tech Tidewater AREC in Suffolk, VA have been evaluated on a weekly basis, and as in prior years, the first report of SBR in Virginia was from one of these sentinel plots. Other diseases in soybeans at this time include Cercospora blight, brown spot, frogeye leaf spot, and anthracnose.

Risk of yield loss in soybean is minimal if SBR is detected following the R6 development stage. However, growers with soybeans that have not yet reached the R6 stage should consider spraying fungicides for control of SBR (triazole or pre-mix fungicide). This is particularly relevant for late-maturing/double-cropped soybean.

Updates will be emailed weekly as we track the progress of SBR spread and disease development throughout Virginia.

NOTE: I would like to introduce myself as the new Extension Plant Pathologist (replacement for Dr. Pat Phipps) at the Virginia Tech Tidewater AREC in Suffolk, VA. My focus is plant disease management in field crops for the state of Virginia. My contact information is the following: Hillary L. Mehl, Ph.D.
Assistant Professor of Plant Pathology; Virginia Tech Tidewater AREC, 6321 Holland Road, Suffolk, VA 23437; Telephone: (757) 657-6450, ext. 423; Cell: (530) 906-0807; email: hlmehl@vt.edu

Kudzu bug distribution in Virginia–Aug. 22 update

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Please click “More” to view the Aug. 22, 2013 distribution map of kudzu bug in Virginia soybean and other hosts. Also in the attachment is the percent control of a long list of insecticides for kudzu bug (courtesy of Jeremy Greene at University of Georgia and Phillip Roberts at Clemson University). If you are at kudzu bug threshold (1 nymph per sweep) and decide to treat your field, you may want to consider a product (or one with similar active ingredients) from the list that has a high percent control. When choosing a product, please keep in mind any other pests that are present in your field. And, please read and follow the label. Additional information: kudzu-bug-distribution-va-2013-pdf

Brown marmorated stink bug (BMSB) update for soybean

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Please click “”More”” to view the most recent update on BMSB distribution in Virginia soybean (please see slide 1 of the attached pdf document). On August 20, our soybean scout Ed Seymore reported that in the last week stink bugs have started to move out of corn and into soybean fields in the counties of Culpeper, Fauquier, Franklin, King George, Rappahannock, Rockingham, Spotsylvania and Stafford. These counties have reached the threshold for stink bugs of 5 stink bugs in 15 sweeps (in the fields that we scouted). Attention should be paid to fields that border corn and woods especially with the tree of heaven (end report from Mr. Seymore). Note that thresholds in soybean do not distinguish between BMSB and native green and brown stink bug species (also shown on slide 1). Dr. Herbert’’s insecticide efficacy trials and on-farm edge treatment research suggest that most insecticides provide initial stink bug knock down (please refer to slides 2 and 3 for efficacy trial results, where the higher percent control, the better). Residual activity varies, and reinvasion can occur after loss of residual protection. Since BMSB exhibit a strong soybean field edge preference, perimeter-only treatments may be effective. Please remember to always base management decisions on proper scouting and thresholds, and always read and follow the pesticide label (sometimes, products and/or rates that we include in our tests are experimental; also, product labels and rates may change from year to year). Additional information: bmsb-pdf

Soybean aphids spotted in Essex County Virginia: Refresher on Thresholds and Sampling

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I just got a report of a soybean aphid infestation in Essex County. It has been several years since we have seen soybean aphid in Virginia, but the summer conditions (generally cooler, overcast) favor development of that pest. Reports of spotty infestations are also coming in from other states, North Carolina included.

As a reminder, the current economic threshold for aphids is an average of 250 aphids per plant, on two consecutive field visits spaced about 5-7 days apart (hit the ‘more’ button for more). This is because aphid populations can ‘crash’ quickly due to heavy pressure by natural enemies like lady beetles, parasitic wasps, and fungal diseases. When scouting, choose a ‘Z’ or ‘W’ shaped pattern to cover the entire field and sample at last 20 to 30 plants per field by examining the entire plant including stems and upper and lower leaf surfaces. Use the aphid/plant average for determining the need for treatment. The threshold applies to soybean through the R5 growth stage (3 mm long seed in the pod at one of the four uppermost nodes on the main stem), after which time plants can tolerate 1,000+ aphids with no threat to yield.
Additional information: soybean-aphid-threshold-ppt

Virginia distribution maps of kudzu bug and brown marmorated stink bug–Aug. 1, 2013

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Attached (click “More”) are the Virginia distribution maps for kudzu bug and brown marmorated stink bug as of Aug. 1, 2013. We will continue to provide updates throughout the season. Thanks to our scouts Ed Seymore, Jamie Hogue, and staff at the Tidewater AREC for their hard work and reports. Additional assistance from Virginia Cooperative Extension ANR Agents, Virginia Tech faculty and staff, Wayne Gardner (Univ. of Georgia), and others is greatly appreciated. Additional information: kb-bmsb-map-pdf