Mortality of Eggs and Newly Hatched Larvae of Lobesia botrana (Lepidoptera: Tortricidae) Exposed to High Temperatures in the Laboratory

The hypothesis that bunch-zone leaf removal reduces infestations of the European grapevine moth, Lobesia botrana (Denis & Schiffermuller) (Lepidoptera: Tortricidae), by increasing egg and larval mortality owing to sunlight exposure was evaluated in the laboratory by subjecting different egg stages (white, red-eyes, and blackhead) and newly hatched larvae to high temperatures. Based on temperatures recorded in a northern Italian vineyard on sun-exposed berries belonging to south-west facing bunches, eggs were subjected to constant temperatures of 40 degrees C and 37 degrees C for one or two periods of 3 or 6 h, and to 24-h temperature cycle with peak of 40 degrees C. Larvae were exposed to 24-h high-temperature cycles with peaks of 35, 37, and 40 degrees C. The results showed partial egg mortality at 40 degrees C, increasing with exposure hours and periods, and as eggs matured. Egg mortality was not affected by exposure to 37 degrees C. Larval survival already decreased significantly at 37 degrees C and was even lower at 40 degrees C. These laboratory data are in agreement with the hypothesis that temperatures reached by berries exposed to sunlight cause egg and larval mortality. Data on egg and larval susceptibility to high temperatures have also implications for species distribution and effects of climate change.