Reproductive Biology of Vine and Grape Mealybugs and its Possible Effects on Detection, Sampling, and Control of Mealybugs
The goal of this project is to elucidate the reproductive biology of mealybugs infesting vineyards in the western United States. We were particularly interested in reproductive parameters that might have implications for the use of pheromones for monitoring or control of these mealybugs. Despite their pest status, remarkably little information is available about reproduction in mealybugs, such as whether males and females mate only once or multiple times and the frequency of mating events. During the 2010 funding cycle, the following progress was made: ? We determined that vine and grape mealybug females must be mated in order to reproduce. There is no parthenogenetic reproduction. ? We showed that both sexes of vine and grape mealybugs can mate multiple times, both on the same day and over a period of several days. ? After emergence from the cocoon, males of vine and grape mealybugs can live up to 4.5 and 7 days, respectively, whereas females live much longer (up to several months). ? Exposure to the sex pheromone produced by female mealybugs did not accelerate the development or emergence of male vine mealybugs, whereas grape mealybug males became active more quickly when exposed to pheromone. However, there was no effect of pheromone exposure on male longevity for either species. ? Although female vine and grape mealybugs will mate multiple times, they only need to mate once in order to maximize their production of offspring. Overall, these results have important implications for using pheromone for monitoring or control of these mealybug species. For example, because male vine and grape mealybugs can mate multiple times over a period of days, a relatively small number of males can inseminate most of the available females. Thus, for effective pheromone-based mating disruption, the pheromone coverage must be good, so that all males are prevented from finding mates for their entire flight period/generation. Thus, a method such as attract-and-kill using pheromone baits treated with a toxicant, that removes males from the population as soon as they contact the lure, might be as or more effective than mating disruption. In terms of using pheromone-based methods for detection and monitoring of populations, when crops are treated are not treated with pesticides, pheromone-baited traps should provide a very sensitive, reliable, and species-specific method of detection of mealybug infestations, and possibly an estimate of population sizes. However, in areas with frequent insecticide use, trap catches may be artificially low due to the greater sensitivity of male mealybugs to insecticides than females. In such cases, manual sampling or visual inspections of plants for infestations can be used as a backup.