RESEARCH ARTICLES/INFORMATION

Research Category: Soybean Disease and Insect Control Year: 2004 Researcher: Art Schaafsma Institution: U of Guelph Topic: Soybean reponse to seed treatments and insecticide foliar spray on populations of soybean aphid and impact on natural controls Funding: $10,000 Research Details: Widespread infestations of soybean aphid across Ontario in 2001 and 2003 have been devastating to the soybean industry. When aphids were controlled with an insecticide in side-by-side comparisons with no spray treatment in farm fields across the province in 2003 -- yield increases ranged from 5 to 20 bu/ac -- with an average yield increase of 9.7 bu/ac. Assuming this average loss in yield on 2 million acres across the province at $10/bushel, soybean aphid may have cost the soybean industry $194 million in 2003. Following the 2003 season, researchers are in consensus on recommending thresholds and other criteria to determine whether or not a field should be sprayed with an insecticide for economic control of soybean aphid. Because aphid populations have a potential of doubling every two days, growers need to scout their fields frequently to assess the growth of aphid populations. The decision to apply an insecticide for aphid control depends on this growth potential of aphid populations, plus other criteria such as stage of soybean development, temperatures, and whether or not the soybean plant is under stress. Insecticide applications are not recommended when thresholds and criteria are not met; therefore, knowing when not to spray can maintain populations of beneficial insects, reduce production costs, and reduce environmental concerns. Now that general recommendations have been established for insecticide control, other control options need to be investigated for controlling aphid populations. Activity of insecticide seed treatments on aphid populations has not been investigated across multiple field locations, or compared with insecticide spray treatments. It can be argued that effective seed treatments may be more favorable to the environment than spray insecticides, because of systemic activity of the insecticide within the soybean plant, rather than destroying beneficial insects within the crop canopy. Therefore, the objectives of this study are to investigate the effectiveness of new seed treatment insecticides on soybean establishment and yield, to determine seed treatment effects on soybean aphid populations compared to insecticide spray application(s) and to validate the decision thresholds developed by the soybean entomologist working group in Chicago, in Dec 03. File: