ABSTRACT
Plum curculio, Conotrachelus nenuphar (Herbst), has become an important pest of highbush blueberries in the northeastern United States. Here, we conducted experiments in 2010-2013 to compare the efficacy of semiochemical-baited traps for C. nenuphar versus conventional (beating cloth) sampling methods in blueberries, and to understand the seasonal abundance and distribution of C. nenuphar adults within and among blueberry fields using these traps. Black pyramid traps baited with the C. nenuphar aggregation pheromone grandisoic acid and the fruit volatile benzaldehyde caught three to four times more adults than unbaited traps without causing an increase in injury to berries in neighboring bushes. Numbers of adult weevils caught in traps correlated with those on bushes (beating cloth samples), indicating that trap counts can predict C. nenuphar abundance in the field. Early in the season, traps placed 20 m from field edges near a forest caught higher C. nenuphar numbers than traps placed at farther distances, suggesting movement of overwintered weevils from outside fields. Using a trapping network across multiple fields in an organic farm, we found evidence of C. nenuphar aggregation in "hotspots"; early in the season, C. nenuphar numbers in traps were higher in the middle of fields, and there was a correlation between these numbers and distance from the forest in 2013 but not in 2012. These results show that semiochemical-baited traps are effective in capturing C. nenuphar adults in blueberries, and that these traps should be placed in the interior of fields preferably, but not exclusively, near wooded habitats to maximize their efficacy.
Subject(s)
Benzaldehydes/pharmacology , Blueberry Plants , Cyclobutanes/pharmacology , Insect Control/methods , Pheromones/pharmacology , Weevils/physiology , Animals , Blueberry Plants/growth & development , New Jersey , Population Dynamics , SeasonsABSTRACT
Synchronization between a parasitoid and its preferred host is an essential strategy for successful biological control. Two ecotypes of Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae) in North America are distinguished by their voltinism. In this study, the differential impact of a specialist parasitoid, Macrocentrus cingulum Brischke (Hymenoptera: Braconidae), on the univoltine and multivoltine populations of O. nubilalis is investigated. Four years of field and laboratory study suggested that M. cingulum emergence was synchronized with the spring emergence of the multivoltine ecotypes of O. nubilalis in Pennsylvania. Univoltine populations experienced minimal parasitism from M. cingulum. Field-collected data suggested that the postdiapause multivoltine O. nubilalis field population was male biased, whereas the univoltine population was female biased. M. cingulum-parasitized postdiapause O. nubilalis larvae were significantly heavier than the male and nonparasitized female larvae. Sex ratio differences observed in overwintered O. nubilalis populations in the presence or absence of M. cingulum parasitism suggested preferential parasitism between male and female O. nubilalis larvae. Correlation between the larger parasitized O. nubilalis larval host and the number of adult parasitoids emerging per host suggested a potential evolutionary advantage to parasitizing female or larger hosts.
