The two field locations were scouted weekly for soybean aphid populations starting in late June and through mid-September when the populations decreased by more than 75% after one week. Cumulative aphid days (CAD) were generally lower this year compared to last year’s data. At the northeast location, aphid-susceptible plots had an average of 1172 ± 196 CAD; for the northwest location, only 188 ± 11 CAD. During the second week of October, both locations were harvested. Soil samples were taken on the days of harvest and will be processed for determining fall populations of soybean cyst nematode (SCN).
Harvest data for the northeast location was put into a mixed-model analysis of variance (ANOVA) and shows significant effects of seed treatment and its interactions with host plant resistance for soybean aphid or SCN. Pooling together all four varieties of soybeans, the plots with the Avicta Complete seed treatment yielded an average of 51.9 bushels/acre compared to the naked (no seed treatment) plots that yielded 44.1 bushels/acre. The same pattern holds true when we only look at the two nematode-susceptible beans. Again, the Avicta Complete treated beans yield significantly higher than the untreated beans. Once we have quantified SCN populations, we can determine whether or not the pest directly impacted yields and if the seed treatment helped to suppress the pest.
Eric Clifton will present data from both the 2013 and 2014 seasons of this project for a ten-minute competitive talk at the Entomological Society of America’s annual meeting that is being held Portland, Oregon on November 2014.