DISTRIBUTION OF THE GREEN ANT, OECOPHYLLA-SMARAGDINA (F) (HYMENOPTERA, FORMICIDAE), IN RELATION TO NATIVE VEGETATION AND THE INSECT PESTS IN CASHEW PLANTATIONS IN AUSTRALIA

The effect of native vegetation on the distribution of the green ant, Oecophylla smaragdina, and the main insect pests in cashew, Anacardium occidentale, plantations in tropical northern Australia was studied b y field surveys and by observations. O. smaragdina was an efficient pr edator and the most abundant ant species in cashew plantations. Infest ations of the main insect pests in the trees lacking ant nests were si gnificantly higher than in those with ant nests. Although O. smaragdin a were abundant on a wider range of native tree species, they preferre d Acacia aulacocarpa and Planchonia careya, and they also thrived on c ashew trees after dispersing into cashew plantations. In cashew planta tions, O. smaragdina preferentially colonized trees with thick canopie s irrespective of tree height. Fierce fights between O. smaragdina col onies were a major factor responsible for changes in population sizes, colonization and distribution of O. smaragdina in cashew plantations. The availability of preferred native trees and the distance between t he native vegetation and the cashew plantation appear to play importan t roles in both the rate and the pattern of initial colonization of ca shew plantations by O. smaragdina. These factors also indirectly influ ence the distribution and abundance of the insect pests of cashews. We suggest that, in the management of modern cashew crops, managers cann ot rely on the natural dispersal of O. smaragdina to control insect pe sts. We recommend the use of native trees to enhance O. smaragdina pop ulations in controlling cashew insect pests.