Evidence for Soybean Aphid (Hemiptera: Aphididae) Resistance to Pyrethroid Insecticides in the Upper Midwestern United States

Abstract

Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is a damaging invasive pest of soybean in the upper Midwest. Threshold-based insecticide applications are the primary control method for soybean aphid, but few insecticide groups are available (i.e., pyrethroids, organophosphates, and neonicotinoids). To quantify current levels of soybean aphid susceptibility to pyrethroids in the upper Midwest and monitor for insecticide resistance, leaf-dip bioassays were performed with λ-cyhalothrin in 2013-2015, and glass-vial bioassays were performed with λ-cyhalothrin and bifenthrin in 2015 and 2016. Soybean aphids were collected from 27 population-years in Minnesota and northern Iowa, and were compared with a susceptible laboratory colony with no known insecticide exposure since discovery of soybean aphid in North America in 2000. Field-collected aphids from some locations in leaf-dip and glass-vial bioassays had significantly lower rates of insecticide-induced mortality compared with the laboratory population, although field population susceptibility varied by year. In response to sublethal concentrations of λ-cyhalothrin, adult aphids from some locations required higher concentrations of insecticide to reduce nymph production compared with the laboratory population. The most resistant field population demonstrated 39-fold decreased mortality compared with the laboratory population. The resistance documented in this study, although relatively low for most field populations, indicates that there has been repeated selection pressure for pyrethroid resistance in some soybean aphid populations. Integrated pest management and insecticide resistance management should be practiced to slow further development of soybean aphid resistance to pyrethroids.

Soybean aphid (Hemiptera: Aphididae) response to lambda‐cyhalothrin varies with its virulence status to aphid‐resistant soybean

“…The corrected mortality for adult aphids exposed to the LC 25 was 23.70% and 25.02% for avirulent and virulent aphids, respectively. Our estimate of the LC 50 (0.40 ± 0.17 μg mL −1 ) for the avirulent soybean aphid is similar to the LC 50 (0.32–0.44 μg mL −1 ) reported by Hanson using leaf‐dip bioassays to evaluate the susceptibility of biotype 1 to lambda‐cyhalothrin. This comparison suggests that our estimate is within the range of what others have reported for avirulent soybean aphid populations.…”

“…Assessment of mortality was performed after 24 and 48 h and data from 48 h post treatment was used to estimate the LC 50 . Aphids unable to right themselves within 10 s after they were turned on their backs were considered dead . Each cup contained 20 aphids and was considered an experimental unit, and each concentration of lambda‐cyhalothrin and the control was replicated three times.…”

Efficacy of afidopyropen against soybean aphid (Hemiptera: Aphididae) and toxicity to natural enemies

“…Management of A. glycines continues to rely on threshold‐based applications of foliar insecticides . Due to development of resistance to pyrethroids by A. glycines and continued regulatory threats to registration of organophosphates (i.e. chlorpyrifos) and neonicotinoids, there is a need for additional insecticide groups for continued management of this pest .…”

“…Reliance on insecticides often results in pests developing resistance to those insecticides . Resistance of A. glycines to pyrethroid insecticides was first documented in North America in 2015 . Laboratory bioassays showing resistance and reports of pyrethroids failing to control field infestations of A. glycines indicate a recurring problem (i.e.…”

“…multiple consecutive years) covering a broad geography (i.e. Minnesota, Iowa, South Dakota, North Dakota and Manitoba) . Pyrethroid resistance in A. glycines threatens the current insecticide‐based management programs for this pest .…”