ABUNDANCE OF LEAF ROLLERS AND THEIR PARASITOIDS ON SELECTED HOST PLANTS IN NEW-ZEALAND

The comparative abundance of orchard pest leafroller larvae was determ ined on eight host plants in the vicinity of pipfruit orchards. The gr eatest numbers occurred in Canterbury, followed by Nelson, Hawke's Bay , and Central Otago. In Hawke's Bay, leafroller larvae were Ctenopseus tis obliquana (41%), Planotortrix octo(15%), Epiphyas postvittana (16% ), and Cnephasia jactatana (9%), smd were most abundant on poplar, wil low, and alder. In Nelson, leafrollers were E. postvittana (25%), Plan otortrix excessana (23%), C. obliquana (23%), smd C. herana (22%), fou nd on willow, alder, clover, poplar, gorse, broom, dock, and plantain. In Canterbury, larvae were C. herana (51%), E. postvittana (34%), and P. octo (15%), mainly on broom, gorse, alder, poplar, dock, and clove r. Leafrollers were very rare on host plants sampled in Central Otago, despite their pest status in horticulture. A total of 1460 larvae wer e reared to adults from the four regions, with 31% parasitism, of whic h two thirds were Dolichogenidea tasmanica (Braconidae). Parasitism va ried significantly between leafroller larval host plants. Removal of l eafroller host plants through mowing, pruning, careful shelter selecti on or other means could usefully reduce the leafroller pest density, a nd risk of incidence on crops.