The control efficacy of the weaver ant, Oecophylla smaragdina (Hymenoptera: Formicidae), on the mango leafhopper, Idioscopus nitidulus (Hemiptera: Cicadellidea) in mango orchards in the Northern Territory

Abstract

The mango leafhopper, Idioscopus nitidulus (Walker), is one of the most serious mango insect pests in the Oriental region. It was first detected in Darwin in the Northern Territory in 1997, and it has been one of the major mango insect pests since 1998. Successful control can be achieved by conventional growers with regular sprays of chemical insecticides, but no suitable control methods are available for organic growers. Weaver ants, Oecophylla smaragdina (Fabricius), have been used to control the main insect pests in cashew orchards since 1998. Three series of field experiments and five field surveys were conducted from 2001 to 2003 in the Darwin area to evaluate whether weaver ants, which are usually abundant in non-sprayed mango orchards, have the potential to control the mango leafhopper. In the field experiments, an average 3.2% of floral shoots and 10.9% of foliar shoots were damaged in the weaver ant treatment, which was similar to or better than in the insecticide treatment (6.7% of floral shoots and 29.9% of foliar shoots damaged). In the treatment without weaver ants or insecticides, the average damage was 30% for floral shoots and 53.4% for foliar shoots. In the field surveys, an average of 4.4% floral shoots were damaged on trees with abundant weaver ants, while 17.5% were damaged on trees with fewer weaver ants and 18.6% on trees with other ant species or no ants. This work indicates that weaver ants are efficient biocontrol agents of the mango leafhopper, and that it is important to maintain the ants at high levels for successful control of the leafhopper. Various aspects of using weaver ants in mango orchards are discussed.

Keywords:

• Biological control agent
• predacious ant
• mango insect pest
• organic produce

Acknowledgements

The study was supported by the Australian Centre for International Agricultural Research. We are grateful to Mr Les Brigden, Ms Liz Marshall, Mr Malcolm Green, Mr Peter Gilson and Philip Stuart for providing us with the study sites and the necessary farm facilities. We thank Mr Matthew Shortus, Mr Les Brigden and Ms Lanni Zhang for their technical assistance.