Soybean Research

Sustainable management of soybean aphids
Dr. Rebecca Hallett, University of Guelph; Dr. Art Schaafsma, University of Guelph, Ridgetown Campus; Dr. Mark Sears, University of Guelph

This project is part of a larger program to develop a comprehensive, sustainable management program for soybean aphid (SBA) control in conventional soybeans.

Conventional soybean producers have two products available for aphid control (lambda-cyhalothrin and dimethoate), which are relatively old chemistries with undesirable impacts on natural enemies. Increasing awareness of the importance of natural enemies coupled with the transition to reduce risk products will help to reduce pesticide use and environmental impacts in soybean systems. This program will result in the development of a sustainable SBA management program utilizing natural enemies and compatible pesticides in conventional soybeans.

In 2008, field efficacy trials were conducted with two registered and four novel insecticides. Two of the novel products show promise for aphid control: spirotetramat and flonicamid. However aphid numbers were quite low in 2008 trials. No differences were found with regard to natural enemy impact, due to low numbers of natural enemies. We intend to repeat our field trials in 2009 when higher aphid numbers are expected.
Environmental Impact Quotient (EIQ) and EIQ Field Use Ratings (EIQ-FUR) were determined in order to identify candidate pesticides for registration that may have lower environmental impacts than currently registered products. All novel products had lower EIQs than both lambda-cyhalothrin and dimethoate, but none had lower EIQ-FURs than lambda-cyhalothrin. However, several novel products had considerably lower EIQ-FURs than dimethoate, so replacement of dimethoate with one or more of those products would result in a reduction of pesticide risk.

The dynamic action threshold approach utilizes pest and natural enemy numbers, as well as expected population growth rates; an insecticide application is only triggered if natural enemy numbers are not sufficient to keep pest populations in check. We have developed a prototype “Natural Enemy Unit Calculator” and “Dynamic Action Threshold Calculator” that can be used to determine whether the action threshold will be reached in the upcoming week and therefore whether an insecticide application is necessary. We have also designed a hand-held disk-style calculator that will simplify this process for growers, and are looking for growers to try this method in 2009 operational scale field trials. This disk calculator will be modified following 2009 operational trials and produced as an extension tool, if it proves effective.