Integrated pest management in mango orchards in the Northern Territory Australia, using the weaver ant, Oecophylla smaragdina, (Hymenoptera: Formicidae) as a key element

Mango is the most important commercial fruit crop in the Northern Territory, Australia. Growers currently rely on insecticides to control insect pests of mango, resulting in environmental and social problems. To reduce dependency on insecticides, a suitable IPM programme is needed. Previous work showed that weaver ants can control the major mango insect pests, but they protect soft scales, damage fruits by their formic acid and annoy operatives during fruit harvest. Further research addressing these constraints showed that certain chemicals can reduce soft scale numbers without seriously affecting weaver ant populations, the isolation of ant colonies reduces fruit damage by formic acid, and water spray reduces the ant activity during harvest. A field experiment with two treatments, weaver ants plus soft chemicals (WPS) and weaver ants plus chemical insecticides (CI), was conducted at Howard Springs in the Northern Territory. In two out of the three years, the yield of first class fruit was 20% higher in WTS than in CL This was mostly explained by lower, insect pest damage, lower incidence of mango scab disease and lower infestation of lenticels in WPS. Trees in WPS produced significantly more fruits than in CI in 2002. Overall, trees in WPS resulted in a profit of A$14.50/tree per year, but trees in CI produced only A$8.38/tree per year. During harvest, farmers experienced only minor problems with ant disturbance. An IPM model using weaver ants as a key element is discussed with respect to 'organic' production. � 2005 Taylor & Francis Group Ltd.