Effect of Insecticide Management History on Emergence Phenology and Neonicotinoid Resistance in <I>Leptinotarsa decemlineata</I> (Coleoptera: Chrysomelidae)

Abstract

Emergence phenology and fitness attributes of several Colorado potato beetle, Leptinotarsa decemlineata (Say), populations were measured under field and greenhouse conditions. Anecdotal observations by producers and pest managers in many locations of the upper Midwest increasingly suggested that select populations of Colorado potato beetle were emerging over a longer period in the spring and were less sensitive to systemic neonicotinoids in cultivated potato. These changes in emergence phenology may be related to changes in systemic insecticide concentration over time. Specifically, a prolonged period of adult emergence in the spring increases the potential of low-dose chronic exposure to systemic neonicotinoid insecticides in potato. In 2010 and 2011, our objectives were twofold: 1) establish a common garden experiment to compare the emergence phenology of Colorado potato beetle populations uniquely managed with variable insecticide inputs, and 2) measure postdormancy fitness of emerged adult beetles from among these selected populations. Cumulative adult emergence was modeled with logistic regression. Results from this study found no clear evidence for direct relationships between phenology and management history or resistance. Differences in reproductive capacity, sex ratio, and body size were apparent in some instances. However, these results did not uniformly correspond to one specific form of potato pest management tested here. In this study, long-term reliance on systemic insecticides for Colorado potato beetle control did not serve as a strong predictor for variable life history for selected populations in Wisconsin.

Agricultural fungicides inadvertently influence the fitness of Colorado potato beetles, Leptinotarsa decemlineata, and their susceptibility to insecticides

“…In an effort to avert rapid resistance evolution, pest management practitioners have advocated for the rotation of chemical groups across sequential L . decemlineata generations and further suggest that the interval of re-exposure to specific MoA classes should be maximized to reduce the likelihood of resistance development 16 . Multi-site mode of action fungicides, however, are often not rotated as frequently and are applied multiple times throughout each growing season 15 .…”

“…Beetles in this population remain highly susceptible to imidacloprid 8,16 . Healthy adult beetles were hand-collected from the canopy of potato plants, placed in plastic containers and returned to the University of Wisconsin-Madison.…”

Managing Colorado Potato Beetle Insecticide Resistance: New Tools and Strategies for the Next Decade of Pest Control in Potato

“…On average, fields lost 35 growing degreedays of control per year since the initial registration of imidacloprid in 1995 (Huseth and Groves 2013). Growing degree-day losses corresponded to Ϸ3.3 fewer calendar days of control per year or Ϸ50 d of lost control since registration of neonicotinoids in 1995 (Huseth and Groves 2013). Erosion of neonicotinoid control in these locations is likely representative of L. decemlineata populations across much of the Wisconsin potato production regions.…”

“…L. decemlineata resistance to individual insecticides varies between both local populations and geographic regions (Grafius 1997, Chen et al 2014), but uniformity of L. decemlineata management practices across large geographic extents increases the likelihood of specific patterns of resistance to develop Groves 2013, Huseth et al 2014). Patterns of population-level insensitivity to specific compounds are likely driven by interactions among a combination of factors including genetic predisposition for resistance, farmlevel insecticide use practices, and frequency of potato production in the agroecosystem (Grafius 1997, Szendrei et al 2012, Huseth and Groves 2013, Piiroinen et al 2013, Chen et al 2014. Moreover, repeated failure to control L. decemlineata with industry standard products can result in additional insecticide applications, yield reduction, greater nontarget impacts, and economic losses for potato growers across entire production regions (Grafius 1997).…”

“…Year is represented as a continuous variable for graphical presentation. On average, fields lost 35 growing degreedays of control per year since the initial registration of imidacloprid in 1995 (Huseth and Groves 2013). Growing degree-day losses corresponded to Ϸ3.3 fewer calendar days of control per year or Ϸ50 d of lost control since registration of neonicotinoids in 1995 (Huseth and Groves 2013).…”