Bifenthrin Baseline Susceptibility and Evaluation of Simulated Aerial Applications in Striacosta albicosta (Lepidoptera: Noctuidae)

Abstract

Striacosta albicosta (Smith) is a maize pest that has recently expanded its geographical range into the eastern United States and southeastern Canada. Aerial application of pyrethroids, such as bifenthrin, has been a major practice adopted to manage this pest. Reports of field failure of pyrethroids have increased since 2013. Striacosta albicosta populations were collected in 2016 and 2017 from maize fields in Nebraska, Kansas, and Canada and screened with bifenthrin active ingredient in larval contact dose-response bioassays. Resistance ratios estimated were generally low in 2016 (1.04- to 1.32-fold) with the highest LC50 in North Platte, NE (66.10 ng/cm2) and lowest in Scottsbluff, NE (50.10 ng/cm2). In 2017, O’Neill, NE showed the highest LC50 (100.66 ng/cm2) and Delhi, Canada exhibited the lowest (6.33 ng/cm2), resulting in a resistance ratio variation of 6.02- to 15.90-fold. Implications of bifenthrin resistance levels were further investigated by aerial application simulations. Experiments were conducted with a spray chamber where representative S. albicosta populations were exposed to labeled rates of a commercial bifenthrin formulation. Experiments resulted in 100% mortality for all populations, instars, insecticide rates, and carrier volumes, suggesting that levels of resistance estimated for bifenthrin active ingredient did not seem to impact the efficacy of the correspondent commercial product under controlled conditions. Results obtained from this research indicate that control failures reported in Nebraska could be associated with factors other than insecticide resistance, such as issues with the application technique, environmental conditions during and/or after application, or the insect’s natural behavior. Data generated will assist future S. albicosta resistance management programs.

Contrasting susceptibility of lepidopteran pests to diamide and pyrethroid insecticides in a region of overwintering and migratory intersection

“…Issues such as weathering, application speed and coverage all affect insecticide efficacy in field conditions, and studies show that proper coverage may not be achieved even using state-of-the-art application technology. 67,68 Our results indicate that the risk of control failure is higher for bifenthrin than chlorantraniliprole. It is unlikely that bifenthrin, at the recommended field rate, will provide proper control efficacy (> 80%) of beet armyworm and fall armyworm in the Florida Panhandle (Fig.…”

“…In this situation, the estimates of expected mortality obtained were intentionally overestimated and should not be taken as actual rates of larval mortality under field conditions. Issues such as weathering, application speed and coverage all affect insecticide efficacy in field conditions, and studies show that proper coverage may not be achieved even using state‐of‐the‐art application technology 67,68 . Our results indicate that the risk of control failure is higher for bifenthrin than chlorantraniliprole.…”

“…The rotation of insecticides with different modes of action is one of the strategies recommended to delay resistance in lepidopteran pest populations 34 . Although managing pest susceptibility is central, other factors can reduce the efficacy of chemical control, including inadequate spray coverage, insufficient field rates, poor application timing or spraying in late insect developmental stages 30,68,69 . These operational factors also should be considered when designing a locally adapted IRM program.…”

Susceptibility and field exposure of Striacosta albicosta (Lepidoptera: Noctuidae) eggs and larvae in Ontario, Canada to four insecticides

“…To date, there have been no reports of reduced insecticide efficacy against S. albicosta in Ontario; however, without baseline susceptibility determination before extensive insecticide use in the region, we cannot determine whether changes in susceptibility have occurred. In a recent survey of S. albicosta management practices in Nebraska, one‐third of respondents reported decreased efficacy with pyrethroid insecticides 43 ; however, this was not supported by laboratory bioassays 44–46 . Regardless, with Canada and the United States relying on similar insecticides for S. albicosta management, there is a need to prioritize resistance management to preserve insecticide efficacy and protect against resistance spread within migratory S. albicosta populations.…”

“…In a recent survey of S. albicosta management practices in Nebraska, one-third of respondents reported decreased efficacy with pyrethroid insecticides 43 ; however, this was not supported by laboratory bioassays. [44][45][46] Regardless, with Canada and the United States relying on similar insecticides for S. albicosta management, there is a need to prioritize resistance management to preserve insecticide efficacy and protect against resistance spread within migratory S. albicosta populations.…”