Development and Evaluation of Degree-Day Models for Acrolepiopsis assectella (Lepidoptera: Acrolepiidae) Based on Hosts and Flight Patterns.

The leek moth, Acrolepiopsis assectella (Zeller), was first discovered in Ottawa, Canada, during the 1993 growing season, representing the first known occurrence of this species in North America. Since then, it has become a significant concern in Allium vegetable production including garlic, leeks, and onions. Acrolepiopsis assectella was first detected in the contiguous United States during the 2009 growing season in northern New York. In this study, we evaluated the development of the US A. assectella population in the laboratory and commercial onion fields. Our results showed that this population required 443.9 degree-days to complete its life cycle on onions in the laboratory. The development of A. assectella on onion did not significantly differ from populations reared on garlic or leeks. Field studies revealed three distinct flight periods for overwintered, first- and second-generation adult males in northern New York. Life cycle duration in the field ranged from 4 to 8 wk. The degree-day prediction model evaluated in this study provided accurate estimates of the occurrence of the following generation. We conclude that this model can help growers to implement appropriate management strategies for different life stages in a timely manner and lessen damage by this new invasive pest.

Patterns of variation in the seasonal dynamics of Listronotus maculicollis (Coleoptera: Curculionidae) populations on golf course turf.

Listronotus maculicollis (Kirby) is a burgeoning pest of Poa annua L. in the northeast United States. To develop an understanding of its spatial and temporal association with golf course landscapes, we described the patterns of variation in certain population parameters across site (Fayetteville and Ithaca, NY), year (2004-2006), and management habitat (fairway, intermediaterough, rough). In weekly surveys along fairway transects, we sampled larvae (identified to instar) by soil core extraction and adults (identified to sex and maturation)by hand collection. Five instars were confirmed based on head capsule width measurements; there was no overlap among instars. Sex ratio was significantly male-skewed on the rough versus the fairway. Insect load, a measure of population size based on cumulative insect-days, varied from 3.0- to 18.5-fold across sites and years and averaged 8.7- and 8.0-fold greater on the fairway than rough for larvae and adults, respectively. Visual assessment of stage-specific population fluctuation curves revealed no divergence in adult males and females, i.e., no evidence of protandry. Variation was greater by year than by site in terms of overall shape of the fluctuation curves, relative abundance of overwintered to spring and summer adults, population synchrony, and number of generations (two to three). Evidence of bimodal spring generations showed that early season population synchrony may be linked to the pattern of adults transitioning from overwintering to developmental habitats. The magnitude of variation in population dynamics underscores the relevance of decision-making strategies and has implications for improving both the spatial and temporal targeting of intervention tactics.