SEASONAL DIAPAUSE DEVELOPMENT, EFFECTS OF TEMPERATURE AND PHOTOPERIOD ON POSTDIAPAUSE EGG DEVELOPMENT, AND VALIDATION OF A DEGREE-DAY MODEL PREDICTING LARVAL ECLOSION OF BLUEBERRY LEAFTIER, CROESIA CURVALANA (KEARFOTT) (LEPIDOPTERA: TORTRICIDAE)

Abstract

AbstractEggs of blueberry leaftier, Croesia curvalana (Kearfott), were transferred from outdoors at 15-day intervals from 15 November to 1 March and held in the laboratory at 20°C, 16L:8D. Mean hatching time continually decreased with each successive transfer date and was significantly shorter for eggs transferred on 1 March compared with any previous transfer date. Transfer date also had a significant effect on percentage hatch, which generally increased with longer exposure of eggs to outdoor conditions. Mean hatching time was longer under 10L:14D photoperiod than at 13L:11D or 16L:8D conditions at all three temperatures studied. Rate of postdiapause development was linearly related to constant temperatures in the range from 6 to 25°C, but appeared to have deviated from linearity at 30°C. The lower threshold temperature for postdiapause development of eggs was estimated to be 3.4°C. Means of 60, 77, and 97 degree-days above a lower threshold of 3.5°C were required for hatching of the 10th, median, and 90th percentile of eggs under laboratory conditions, respectively. In each of 3 years, eclosion of first-instar larvae occurred over a 10- to 17-day period in late April to mid-May. Degree-day accumulations based on litter temperatures in the field predicted the dates of 10th, 50th and 90th percentile eclosion of first-instar larvae within ±2 days of the observed dates.