Paralobesia viteana (Clemens), the grape berry moth (GBM), is a major economic pest of cultivated grapes in Eastern North America. Although pheromone lures and traps are available for monitoring this pest, male moth captures in these traps are not consistent between Michigan grape-growing regions, and male captures decline as the infestation increases through the multiple generations that occur during a season. This makes it difficult to use traps to monitor this pest’s population dynamics and complicates the timing of pest management activities. Substantial regional variation exists in the magnitude of the response of male GBM to sex pheromone-baited traps in Michigan vineyards. Males are readily captured in traps in the southwest region, whereas in the northwest very few males are captured. However grape berry moth larval infestation is found in fruit in both regions. Using Y-tube choice tests and trapping trials with captive females, I determined that males from Southwest and Northwest Michigan responded similarly to the standard pheromone blend, and males did not preferentially choose females from the same population. From these results I conclude that the regional differences in male captures are not due to differential responses of males in these respective areas. I postulate that the reason fewer males are trapped in Northwest Michigan is because the P. viteana population is much smaller than in Southwest Michigan. To test whether seasonal changes in the plant canopy affect captures of male grape berry moth, I manipulated grapevine fruit density or canopy structure in multiple growing seasons, and measured male captures under these conditions. Removal of either 50 or 100% of the fruit clusters from vineyard plots did not consistently affect captures in pheromone traps. In a separate canopy manipulation experiment, I detected significant differences in male captures between unaltered and open canopies for some sample periods, and there was a trend toward numerically more male captures in unaltered than in open canopies. I conclude that fruit presence, fruit density and canopy fullness do not reduce male P. viteana captures late in the season, and thus do not explain the seasonal pattern of development and abundance of this insect.Experiments that measured the frequency, intensity and duration of mating and reproductive behaviors in colonies held under different temperature and photoperiodic conditions were used to determine that temperature is the likely driving force behind the seasonal variation in male P. viteana captures, and thus shapes the observed phenology of this pest. The frequency of male flights, mating and oviposition increased with temperature. This amplified activity helps to explain the intensification of oviposition and subsequent larval feeding damage in vineyards during the summer and early fall when conditions are warm. My data also show the proportion of male flights that occur when females are not receptive to mating is greater at lower temperatures, which helps explain why more males are trapped in the spring when temperatures are cool. Traps baited with lures that contained different quantities of P. viteana sex pheromone were used to determine that the increased amount of pheromone released by lures during hot periods can reduce male captures. My research shows that temperature is an important factor that governs the behaviors associated with mating and reproduction, and also influences the main tool for monitoring this pest, the pheromone trap. Taken as a whole, the effects of temperature on behavior and trapping strongly shape the observed phenology of this pest.
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