Soybean Aphid Scouting and Management Recommendations 2007

Eileen Cullen, Extension Entomologist, UW Madison Entomology Department 

• Soybean aphid http://www.plantpath.wisc.edu/soyhealth/aglycine.htm
• Soybean Development Stages and Soybean Aphid Thresholds

• Soybean Aphid Management Recommendations 2007

• Soybean Aphid Parasitoids in Wisconsin

• Soybean Aphid Biological Control

• The UW Nutrient and Pest Management program published a Visual Guide to the Number of Soybean Aphids per Leaflet. Each soybean leaflet has a specific number of aphids displayed to help you count Copies can be ordered from the NPM Program at 608-265-2660 or you can print one from the web at www.plantpath.wisc.edu/soyhealth/pdf/sba_scout.pdf.

• To determine if an aphid population is actively increasing, check over several visits. Conditions that favor aphid population growth are cool temperatures, plant stress, particularly drought stress, and a lack of aphid predators.
• Check for mummies and winged females. Do not spray if mummies are numerous or a majority of aphids are winged or developing wings, an indication that the aphids will soon leave the field.
• Plants are likely to be considerably above threshold if stems or pods are covered with aphids and honeydew, sooty mold covers the bottom leaves, and plants are stunted. Insecticide treatment is probably still of value, but the optimal time for treatment (greatest economic return) is past.
• If you are using the speed scouting method, be aware that this method tends to be conservative. Speed scouting is a binomial sampling plan developed at the University of Minnesota and validated through the regional soybean aphid project. A binomial sampling plan is based on a specific worksheet tally leading to one of three decisions (do not treat, treat, resample field in 5-7 days). Speed scouting takes less time than traditional whole plant sampling, but because it tends to overestimate, do not spray unless a positive treatment decision occurs for TWO weeks running. A worksheet is required for the speed scouting method. You can print one from the University of Minnesota Aphid Speed Scouting webpage http://www.soybeans.umn.edu/crop/insects/aphid/aphid_sampling.htm which also has an overview, examples, and frequently asked questions about aphid speed scouting. This sampling plan was created and intended for use for commercial soybeans in central and southern MN. Because data was not collected past seed set, UMN recommends using this sampling protocol only up to pod set on fields with 30”rows. 

• Pyrethroids (e.g. Warrior, Mustang Max, Asana, Baythroid) have a relatively longer residual, and are most effective at temperatures below 90°F. Organophosphate products (Lorsban) have a fuming action, and may work better in heavy canopies or at higher temperatures.
• Tank mixes of insecticide, fungicide and/or herbicide are not generally recommended. Soybean aphid, disease and weed pests do not all appear at the same time at economically damaging levels, so a single tank mix, while convenient, will not provide satisfactory control of all three pest types. Additionally, sprayer specifications such as water volume, nozzle type (droplet size), and pressure must be optimized for each pest situation.
• Good coverage is important. Higher spray volumes and higher pressure help to move the insecticide down into the canopy.
• Adding insecticide to early-season glyphosate application as "insurance" is not recommended unless aphids are at threshold levels and actively increasing.