TRANSMISSION OF BOTRYTIS-CINEREA TO GRAPES BY GRAPE BERRY MOTH LARVAE

Larvae of Lobesia botrana, the grape berry moth, increase the severity of gray mold on grapes (cv. Sauvignon). The role of larval wounds on the colonization of immature berries by Botrytis cinerea was studied with scanning electron microscopy. On vineyard berries, emergence of conidiophores is favored at the entrance of larval galleries, and fungal development is enhanced at superficial wound sites. A greenhouse trial showed that conidia were introduced inside larval galleries by larvae externally contaminated by the fungus. The germination of conidia and resulting mycelial colonization followed on the inner surfaces of galleries. The role of transport of viable conidia by larvae was also assessed under field conditions. On immature berries, the artificial supply of viable conidia on the cuticle of second-generation larvae caused a significant increase in the percentage of larval injuries infected by B. cinerea (20% for clusters with normal compactness and 10% for thinned clusters after 15 days of larval presence). As for damage to ripe berries, third-generation larvae carrying viable conidia caused a 2.4% increase in disease severity at harvest as compared with larvae carrying dead conidia.