High‐level field‐evolved resistance to spinosad in Colorado potato beetle, Leptinotarsa decemlineata, in organically managed fields

Abstract

BACKGROUND Organic pest management eschews synthetic pesticides and insecticide resistance is rarely studied in organically managed systems. Spinosad is a biologically based insecticide used widely by both organic and conventional growers. Colorado potato beetle, Leptinotarsa decemlineata, is infamous for its ability to evolve resistance to insecticides. Spinosad resistance was surveyed in conventionally managed fields in eastern New York in 2006. In response to grower reports of spinosad failure on two organic farms in 2009, resistance to spinosad was assayed in both conventionally and organically managed fields the following year, and growers were surveyed for their prior spinosad use. RESULTS In 2006, spinosad resistance measured as median lethal dose (LD50) varied 9.8‐fold among the eight conventional fields sampled and a laboratory susceptible strain. In 2010, the resistance ratios of LD50 values relative to a laboratory susceptible strain ranged from 17.5 to 40.6 in conventionally managed fields, and from 128.7 to 5750.3 in organically managed fields, a dramatic increase from 2006 with higher resistance ratios in organically managed fields. Organic growers reported much heavier use of spinosad in the years prior to 2010. CONCLUSION This is the first report of high‐level resistance to spinosad in Coleopterans. Selection strength due to number of years used and number of applications per season appear to have been the primary factors driving the evolution of resistance to spinosad, highlighting the need for resistance management in organic production, where fewer alternative active ingredients for resistance management are available. © 2021 Society of Chemical Industry.

Characterization of Insecticide Response-Associated Transcripts in the Colorado Potato Beetle: Relevance of Selected Cytochrome P450s and Clothianidin

“…Previous work has notably revealed a common over-expression of several transcripts coding for cuticular proteins in the diamondback moth Plutella xylostella treated with five insecticides including chlorantraniliprole and spinosad, supporting a relevance for these targets in insecticide response [ 27 ]. Regarding the latter compound, against which substantial field-evolved resistance has been reported for L. decemlineata notably from organically managed fields [ 28 ], recent work has identified via next-generation sequencing a total of 30 deregulated mRNA transcripts in L. decemlineata submitted to spinosad treatments [ 16 ]. Downregulation of a transcript coding for Mesh yielded a similar efficacy when compared with spinosad in field trials aimed at L. decemlineata larvae [ 29 ].…”

Leveraging RNA Interference to Impact Insecticide Resistance in the Colorado Potato Beetle, Leptinotarsa decemlineata

“…Examples of resistance against other insecticides, in addition to neonicotinoids, have also been reported. An increase in resistance ratios pertaining to spinosad, a mixture of spinosyns A and D, was observed in L. decemlineata populations collected in organically managed fields from eastern New York [ 28 ]. Work assessing the response against a panel of 14 insecticides in seven L. decemlineata populations collected from China revealed strong resistances in select populations towards different insecticides, including cyhalothrin, deltamethrin, and alpha-cypermethrin to name a few [ 29 ].…”

Low-Dose Insecticide Combinations for Colorado Potato Beetle Control

“…Reducing the dosing will also help to prevent or delay populations from developing resistance to the active ingredients spinosyns. According to Arthropod Pesticide Resistance Database (APRD), several cases of spinosad resistance in CPB have been reported, including field evolved resistance [40][41][42], emphasizing the need to find other solutions, such as the use of reduced doses of insecticides or combinations of such reduced doses.…”