Pest Management Science (2021) 77, 4393-4399

Kathleen Schnaars-Uvino and Mitchell B. Baker (2021)
High-level field-evolved resistance to spinosad in Colorado potato beetle, Leptinotarsa decemlineata, in organically managed fields
Pest Management Science 77 (10), 4393-4399
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.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest

---

Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Leptinotarsa decemlineata	Potato (Solanum tuberosum)	U.S.A. (NE)