Trap Captures of Male Grapholita libertina (Lepidoptera: Tortricidae) Moths: Relationship to Larval Numbers and Damage in Wild Lingonberry1

The lingonberry fruitworm, Grapholita libertina Heinrich, is a tortricid moth whose larvae infest wild lingonberry (Vaccinium vitis-idaea L. variety minus Lodd) fields in Newfoundland, Canada. This study investigated the potential for predicting G. libertina larval damage by using adult pheromone trap captures. Spatial patterns of capture were studied in relation to subsequent larval and damaged berry distributions in four wild lingonberry fields during 1998, 1999 and 2000. A model was tested that incorporated the effects of resource availability and coincident plant composition on insect distribution. In 1998 and 2000, the mean adult capture/trap correlated well with larval (R2 = 0.38–0.63) and damaged berry (R2 = 0.41–0.59) density within grids at each site. In 1999, larval and damaged berry densities were not significantly correlated to adult distributions, and were more dependant on a limited host berry distribution (R2 = 0.54 and 0.47, respectively). The results of this study suggest that correlation between adult trapping of G. libertina and subsequent larval distributions is dependant on a minimal host berry population. Other factors that may contribute variability are also discussed.