Biological Control Of Pests
p. 42 · Read in the full issue
In Fiji
BIOLOGICAL control of agricultural pests in Fiji has been highly suc cessful for four main reasons: warm, relatively non-seasonable climate which permits almost uninterrupted breeding of parasites throughout the year; isolation by the Pacific Ocean from other coun tries; indigenous fauna is relatively poor; the main crops are few in number, there by ensuring better organisation.
Outstanding examples of biological control of insect pests in the Colony are the Malayan fly (Ptychomyia remota) against purple coconut moth; the Trina dad ladybird against the coconut scale insect; the wasp (Apanteles tirathabae) and the fly (Erycia basifulva), both from Java, against the spike borer; another Javan wasp against the leaf miner; and, finally, the beetle (Plaesius javanus)— again from Java—against the banana weevil.
These are all examples of introducing insects to check other insects. However checking noxious weeds by introduced in sects is also, of course, possible but presents greater difficulties.
As long ago as 1910 the Mexican seed fly was introduced into Fiji to combat lantana; in 1930, another insect, from Trinadad, was brought in to check Roster’s Curse. The introduction of the South American moth, Cactoblastis cactorum, into Queensland to combat prickly pear, and its almost miraculous success, is one of the most famous ex amples of noxious weed control by in sects.
Some of the factors that must be taken into consideration, however, before an in sect is introduced to kill weeds, are as follows: • The weed to be attacked must be botanically distant from economic plants so that any pests of the former will not be attracted to the latter. For example, the weed Solanum torvum is related to the potato and tomato and any insect that is attracted to the weed will also be attracted to the tomato and potato. • Exhaustive testing under strict quarantine must be undertaken to find out what economic plans, unrelated to the weed, are likely to be attacked as well as the weed. • The need for the habits of weed and insect to coincide. For example, the in sect’s egg-laying must coincide with the flowering of the weed. • Whether or not the weed-attacking insect may be attacked itself, in its new home, by indigenous parasites or by those already established. —Adapted from the Fiji Department of Agriculture Bulletin No. 23.