Orthosia hibisci
Overview
Speckled green fruitworm is one of several members of the Noctuidae fruitworms family which cause damage to fruit and foliage of pome and stone fruit. It was introduced from Europe, the adult being a nocturnal moth, however, it is the larval stage, particularly the large ones that cause unacceptable damage to fruit.
Biology
Green fruitworm overwinters as an adult moth which starts flying (at night) and lays eggs in the spring. Larvae hatch and go through six instars, the later instars being a quite large (one inch) green caterpillar with yellow/white longitudinal stripes. Larvae feed on flowers, fruit and foliage where they can roll leaves similar to true leafrollers. Individual fruitworm larvae can feed on many fruitlets during the post-bloom period, however, many of these damaged fruits will fall off. Fruit that persists to harvest will have deep corky scars and indentations, which is also similar to leafroller feeding from the overwintering generation.
Monitoring
Examine 20 flower/fruit clusters on 5 trees throughout the canopy from pink to first cover. If two or more larvae per tree are found, or there is evidence of feeding damage, treatment is recommended. Pheromone traps can also be deployed to monitor the presence and relative abundance of green fruitworms.
Management
Pre-bloom insecticides are advised, and pyrethroids are the best choice, however, they can be hard on beneficial insects when applied at this time. Post-bloom insecticide applications targeting other insects are generally effective too. B.t. (Dipel) is effective if applied early before the larvae get too big.