Comparing the cost-benefit probability of management based on early-stage and late-stage economic thresholds with that of seed treatment of Aphis glycines.

Background: The current integrated pest management (IPM) curative strategy for soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), relies on responsive spraying foliar insecticides during the R1-R5 soybean stage when aphid abundance reaches the economic threshold (ET) of 250 aphids plant (traditional IPM). By analyzing the relationship between aphid abundance and yield loss before the R1 stage, we developed an early-stage ET. We propose to spray foliar insecticides on plants colonized with aphids using the early-stage ET as a trigger (improved IPM), together with seed treatment to manage A. glycines and delay them exceeding the ET of 250 aphids plant in the late stage for whole-field spraying (traditional IPM). Finally, we compared the cost-benefit probabilities of the three management approaches.

Results: The early-stage ET over all potential yields, market prices, and control costs was 64 aphids plant , providing growers 7 days of preparation time to spray foliar insecticides before the economic injury level of 187 aphids plant was reached. Improved IPM achieved the highest cost-benefit probabilities followed by traditional IPM, and the seed treatment achieved the lowest. However, in fields where the pressure from white grubs was high, the probability of achieving a positive net return with seed treatment was higher than that in other locations.

Conclusion: Improved IPM based on early-stage ET of 64 aphids plant was the most cost-effective of all the three approaches. Neonicotinoid seed treatment can be applied as an insurance strategy to supplement A. glycines IPM in Liaoning, China. © 2022 Society of Chemical Industry.