Direct and indirect influences of the weaver ant Oecophylla smaragdina on citrus farmers' pest perceptions and management practices in the Mekong Delta, Vietnam

Abstract

In the Mekong Delta, Vietnam, the predatory weaver ant Oecophylla smaragdina was abundant in about 75% of the sweet orange and 25% of the Tieu mandarin orchards. With a three-level scale (low, moderate, high), farmers assessed the incidence, severity and yield loss of fruit caused by major pests. With abundant O. smaragdina, sweet orange farmers assessed a lower pest infestation or yield loss for the citrus stinkbug Rhynchocoris humeralis, the aphids Toxoptera aurantii and T. citricidus, the leaf-feeding caterpillars Papilio spp., and inflorescence eaters. In Tieu mandarin, the use of agrochemicals was higher than in sweet orange, and pest risk assessment was not correlated with ant abundance, except for aphid infestation, which was rated lower. The number of sprays targeting a particular pest was positively correlated both with pest incidence and severity ratings and was negatively correlated with ant abundance. Irrespective of O. smaragdina abundance, citrus leafminer Phyllocnistis citrella was one of the major spray targets. Citrus red mite Panonychus citri was the most important target in Tieu mandarin, accounting for 430% of all target sprays. Stimulating O. smaragdina as a biological control agent in Tieu mandarin will only be successful when citrus leafminer and mites can be controlled simultaneously without excessive chemical treatments. The concept of ant predation, well known by most farmers, could be used as a starting point to educate farmers about the existence and role of predatory mites. Farmer participatory training and research that focuses on experiential learning and field observations offers a promising approach to enhance farmers' perceptions of pests, their ecological causalities and non-chemical alternative management options.

Density of pheromone sources of the weaver antOecophylla longinodaaffects oviposition behaviour and damage by mango fruit flies (Diptera: Tephritidae)

“…To illustrate their effectiveness as biological control agents, Dejean (1991) demonstrated that a colony comprising 12 nests may capture about 45,000 prey per year. Oecophylla smaragdina (Fabricius) successfully protects plants against insect herbivores (Van Mele et al 2002), including fruit flies in commercial mango plantation in northern Australia (Peng and Christian 2006). Likewise, the African weaver ant O. longinoda (Latreille) significantly reduces fruit fly infestation, damage being negatively correlated with the number of ant nests in the mango trees (Van Mele et al 2007).…”

Weaver Ant Role in Cashew Orchards in Vietnam

“…A weaver ant technology using weaver ants as a key element has been implemented to control the major insect pests by cashew growers in Australia , Papua New Guinea (Peng 1999(Peng , 2000, East Timor (Amaral 2010), and Mozambique (Peng 2002). Weaver ants, O. smaragdina, are widely distributed in tropical areas of south-east Asia and northern Australia (Lokkers 1986), and they are abundant in Vietnam (Van Mele et al 2002). Weaver ants have been used to control citrus insect pests on the Mekong delta in Vietnam for many years (Van Mele et al 2002), but the role of the ants in cashew orchards has not been explored.…”

Using weaver antsOecophylla smaragdinato control two important pests on African mahoganyKhaya senegalensisin the Northern Territory of Australia

“…Wylie 1974;Macfarlane et al 1976;Lim and Kirton 2003;Peng et al 2010aPeng et al , 2011bPeng et al , 2012 and in horticultural crops (e.g. Stapley 1972;Huang and Yang 1987;Van Mele et al 2002;Peng et al 2004Peng et al , 2010bPeng and Christian 2005a). The effectiveness of weaver ants in biological control has been Australian Forestry, 2013Vol.…”