Pollination biology of cashew in the Northern Territory of Australia.

Aspects of the pollination biology of cashew Anacardium occidentale L. (Anacardiaceae) were investigated at a site of potential commercial production. A mean of 442.9 flowers were produced per panicle of which 32.1 (7.3%) were hermaphrodite, the remainder being male. Mean initial fruit set was 5.0 per panicle, representing a percentage fruit set of 15.5%. The absence of either male or hermaphrodite flowers at any particular stage of flowering did not limit fruit set. Diversity of insect flower visitors, attracted by nectar rewards, was great, but only a few species were common. Three species of potentially efficient pollinators were tested for their pollinator efficiency which was found to be high for honey bees, Apis mellifera, and a native fly, Ligyra sp. Only 25% of flowers were pollinated in 1987, but this increased to 98% owing to a corresponding increase in the natural populations of insect visitors. Wind and night flying insects played no role in pollination. Although 98% of flowers were pollinated, initial fruit set averaged only 15.5%. This suggests that factors other than pollination limit fruit set. However, pollination is important and the insect pollinators will need protection from insecticide applications and destruction of breeding sites.