Predicting the impact of climate change on the overwintering range of corn earworm (Helicoverpa zea): Implications for sweet corn IPM in Minnesota

Corn earworm is an increasingly pervasive pest of sweet corn in the Midwestern U.S. While it is currently assumed to not overwinter north of the 40^th latitude, many questions remain regarding its response to low temperatures (cold hardiness) and potential to expand its overwintering range. Since the magnitude of insect infestations can be positively correlated with overwintering survival, understanding the cold hardiness of an insect could greatly enhance the ability to forecast the timing and magnitude of pest infestations. The objective of this study was to apply laboratory-based cold hardiness measurements of the overwintering stage of corn earworm (pupa) to the ecophysiological model, CLIMEX, in order to estimate potential shifts in corn earworm distribution given future climate projections. In particular, the time to reach 95% pupal mortality was measured for -10ºC, -5ºC, 0ºC, and 5ºC. These values were used as cold stress functions and combined with other life history parameters in CLIMEX, creating a mapped index of the potential for population growth and persistence of this insect in the contiguous United States. CLIMEX was used to provide such projections of geographic suitability to 2080. These predictions will help to offer the most effective integrated pest management (IPM) strategies for northern growers of crops targeted by corn earworm, such as sweet corn.