Weaver ants,Oecophylla smaragdina(Hymenoptera: Formicidae), as biocontrol agents on African mahogany trees,Khaya senegalensis(Sapindales: Meliaceae), in the Northern Territory of Australia

Abstract

African mahogany, Khaya senegalensis, is a high quality timber tree that grows well in the wet-dry tropical areas of Australia. Most trees grown in the latter regions are branched at lower levels on the trunk (a symptom known as 'low-branching'), which limits timber production per tree. Inferring that it may be caused by herbivorous insects, we sought to establish whether low-branching can be reduced by the presence of predatory weaver ants, Oecophylla smaragdina. Two field experiments on young African mahoganies were conducted at two sites in the Darwin area of Australia from 2006 to 2008. Each experiment had two treatments: trees with weaver ants and trees without the ants. Pest damage was found to be the most important correlate of the multiple branching, and weaver ants were effective in limiting the formation of multiple leaders. In 3-year-old mahoganies at Berrimah Farm, the percentage of trees with pest-caused multiple leaders was 4.8% in the weaver ant treatments (WAT) but 45.5% in the treatments without the ants (TWWA). In 2-year-old mahogany coppices at Howard Springs, no trees developed multiple leaders in WAT, but 22% developed such leaders in TWWA. The average pest damage on flushing shoots at both sites was significantly lower in WAT (1.8-2.5%) than in TWWA (22.9-24.9%).

Do Weaver Ant (Hymenoptera: Formicidae) Marks Affect Mango Internal Quality and Storage Life?

“…The weaver ant, Oecophylla smaragdina (F.) (Hymenoptera: Formicidae), is effective in controlling over 50 species of insect pests (e.g., sap-sucking bugs, beetles, caterpillars, thrips, and fruit ßies) on many tropical tree crops (e.g., cashew, citrus, cocoa, coconut, lychee, mango, and oil palm) and forest trees (e.g., African mahogany, eucalyptus, and hoop pine) (Way and Khoo 1992;Peng et al 2004Peng et al , 2010Peng and Christian 2005a;Van Mele 2008). This ant is a tropical species, and it has been used for controlling various pest insects in Australia, China, Papua New Guinea, the Solomon Islands, Thailand, and Vietnam (Peng et al 2004).…”

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

“…African mahogany trees need to be protected from a very young stage (1 m high) (Peng et al 2010a), but such young trees have canopies unsuitable for weaver ants to colonise. Based on our field observations, weaver ants foraged on young mahoganies because the extrafloral nectar secreted by the trees was very attractive to them.…”

“…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).…”

Biological control of the fruit‐spotting bug Amblypelta lutescens using weaver ants Oecophylla smaragdina on African mahoganies in Australia

“…African mahogany trees need to be protected from a young stage (Peng et al, 2010b), although such young trees have unsuitable canopies to support weaver ants. Weaver ants need trees with a suitable canopy in which to live.…”