Effective control of Jarvis's fruit fly, Bactrocera jarvisi (Diptera: Tephritidae), by the weaver ant, Oecophylla smaragdina (Hymenoptera: Formicidae), in mango orchards in the Northern Territory of Australia

Jarvis's fruit fly, Bactrocera jarvisi (Tryon), is a major insect pest in mango production in the Northern Territory of Australia. Chemical insecticides, together with farming strategies, are effective in reducing fruit fly damage, but have resulted in increased costs, the reduction of natural enemies and environmental pollution. For organic growers, no effective options are available. Weaver ants, Oecophylla smaragdina (Fabricius), are effective in controlling many insect pests in citrus, cashew and mango orchards. To determine whether weaver ants have the potential to control Jarvis's fruit fly, field experiments were conducted from 2001 to 2003 at three orchards in northern Australia. Data from a conventional orchard showed that the treatment with weaver ants plus soft chemicals produced lower levels of rejected fruits (0-0.4%) than the treatment with chemical insecticides (0.9-4.7%). In organic or insecticide-free orchards, fruits were much less damaged on trees with weaver ants (?1%) than on trees without the ants (1.5-5.1%). Fewer fruit fly puparia were produced from fruits collected in the weaver ant treatment (0-0.6 puparia/fruit) than from fruits collected in the insecticide treatment (1.2-3.7 puparia/fruit). Green mature fruits produced fewer fruit fly puparia (1.2 puparia/fruit) than ripe fruits (3.7 puparia/fruit). More fruit fly adults were observed in the insecticide treatment (0.8 adult/tree) than in the weaver ant treatment (0.2 adult/tree). This work indicates that weaver ants are efficient biocontrol agents of Jarvis's fruit fly.