Seasonal Abundance, Life History, and Parasitism of <I>Caloptilia porphyretica</I> (Lepidoptera: Gracillariidae), a Leafminer of Highbush Blueberry

Abstract

The leafminer Caloptilia porphyretica Braun (Lepidoptera: Gracillariidae), has become a frequent pest in commercial highbush blueberries, Vaccinium corymbosum L., in New Jersey, but little is known about its seasonal abundance, life history, and parasitism rates. Monitoring programs were conducted from 2003 to 2006 on seven blueberry farms to determine the relative abundance of this leafminer by using pheromone-baited traps and by sampling vegetative and flower/fruit clusters and new shoot growth. We found at least three distinct generations per year, with populations reaching their highest peak in the second generation. Laboratory studies characterized the life history of C. porphyretica and its parasitoid Pholetesor sp. prob. salalicus (Mason). The developmental period of C. porphyretica, from egg to adult, took 927, 838, and 912 degree-days (DD) at 20, 25, and 30 degrees C, respectively, by using a developmental threshold of 4.8 degrees C. This was equivalent to an average of 892 DD to complete development to adult, which compared with 870 and 880 DD between the first and second, and second and third generations, respectively, by using pheromone trap data averaged from 2004 to 2006. Although C. porphyretica populations varied greatly, the number of larvae in cluster and new shoot samples was highly correlated with the number of adults in traps. Field parasitism rate was -29%, with the braconid Pholetesor sp. the most abundant parasitoid. Ten of the 13 parasitoid species collected belonged to the family Eulophidae. When different ages of leafminers were exposed to Pholetesor sp., we found that the parasitoid attacks 9-15-d-old instars that reside in the mines of leaves.