Persistence and Inheritance of Costs of Resistance to Imidacloprid in Colorado Potato Beetle

Abstract

Reduced fitness among resistant versus susceptible individuals slows resistance evolution and makes it easier to manage. A loss of resistance costs could indicate novel adaptations or mutations contributing to resistance. We measured costs of resistance to imidacloprid in a Massachusetts resistant population compared with a Massachusetts susceptible population in 1999 in terms of fecundity, hatching success, egg development time, and sprint speed. Resistance was additive and seemed to be polygenic with high heritability. The fecundity cost appeared overdominant in 1999, and the hatch rate cost was partly recessive in 1999, but neither was significantly different from dominant or recessive. In 2004, we repeated our measures of resistance costs in Massachusetts in terms of fecundity and hatching success, and we added a new resistant population from Maine. In 2005, we compared development time of Maine resistant and the laboratory susceptible colony eggs. Significant fecundity costs of resistance were found in both population in both 1999 and 2004, and significant egg developmental time costs were found in 1999 and 2005. However, the hatching success costs of resistance were significant in 1999 and not apparent in 2004, suggesting some modification or replacement of the resistance genes in the intervening time.

Variable concentration of soil‐applied insecticides in potato over time: implications for management of Leptinotarsa decemlineata

“…Over a period of 5 years, the authors observed a considerable increase in the number of growers reporting loss of efficacy of neonicotinoids. Other studies conducted in intensive potato production areas of the East Coast and Midwest have reported similar losses in levels of control associated with the use of the systemic neonicotinoids …”

Landscape genomics of Colorado potato beetle provides evidence of polygenic adaptation to insecticides

“…Future studies should investigate the importance of spatial and temporal variation in management practices and land cover types to the maintenance of genetic variation among L. decemlineata populations: careful rotation of insecticide modes of action by certain growers, combined with any potential effect of fitness costs associated with resistance to certain chemicals (Alyokhin & Ferro, ; Baker et al., ), may be delaying evolution of resistance. Landscape connectivity may also affect resistance evolution by increasing the strength of genetic drift relative to selection: landscapes with a lower proportion of potato are expected to have lower patch connectivity for L. decemlineata due to greater distances in space and time between rotated potato fields.…”

The Red Queen in a potato field: integrated pest management versus chemical dependency in Colorado potato beetle control

“…Although relative fitness of resistant Colorado potato beetles is often reduced in comparison with susceptible beetles, their mating behavior is likely to ensure high heterozygocity of the offspring. If inheritance of fitness costs is recessive, as has been demonstrated for at least some Colorado potato beetle populations, this is likely to slow down decline in the frequency of resistant alleles in the absence of selection. Furthermore, when resistance is based on preadaptations like utilizing the toxic host plants, resistant genes might be already present in the population, and the costs associated with the resistance might not always be significant .…”