Aspects Affecting Distribution and Dispersal of the Indigenous Heteroptera Complex (Heteroptera: Pentatomidae & Coreidae) in South African Macadamia Orchards

Physical aspects of macadamia orchards appear to play an important role in the distribution patterns of indigenous heteropterans. Increasing tree density and tree height appear to be associated with increases in insect damage. Very dense orchards not only provide these insects with an ideal sheltered habitat, it also reduces the efficacy of many air-assisted sprayers commonly used for insect control in this crop. Macadamias are very tall trees and heteropterans seem to have a preference for nuts occurring in the higher tree strata. The reason for this is unclear at the moment but it might be related to thermoregulation or lekking behaviour. Heteroptera damage was also confined to the edges of many orchards especially during the early season and it is speculated that perimeter trees may temporarily act as a barrier, preventing migration deeper into the orchards. Implications of these findings for an IPM programme are discussed and include: perimeter spraying during the early season as opposed to a full cover spray, tree pruning as well as tree height management.