Irradition-based pest control gains a foothold in South Africa

The South African Mail and Guardian has just featured an article about sterile insect technique (SIT), a method of managing farm pests by rendering them sterile with gamma radiation.

A small private company irradiates some 7-million male Mediterranean fruit fly pupae per week with gamma-rays emanating from a nugget of radioactive cobalt. This renders the emerging insects sterile. They are shipped by the million to fruit farms in the Western Cape area of South Africa, where they mate with “wild” females, making the latter sterile in turn.

Elsewhere in South Africa, another small company breeds millions of ladybirds and wasps on cultures of the mealy bug and red scale pests, grown on a substrate of butternut. The predators and parasites are harvested, packed and sold to citrus and grape farmers throughout the country.

The South African bug industry is tiny compared to its counterparts elsewhere in the world. In Guatemala, the world's largest sterile insect factory produces 2,8-billion fruit flies per week. The largest mass producer of predator insects is a Netherlands-based company which delivers €52-million worth of insects to European tunnel farmers a year.

Integrated pest management requires long-term thinking and a culture change, with farmers’ objections ranging from superstition to real concerns about higher costs and lower efficiencies. It only really starts working if most farmers in an area act together to suppress a pest, and total eradication requires the cooperation of the local non-farming communities as well. The technology is new and risky, and the mass production of insects is difficult and capital-intensive. An insectary’s temperature, humidity and sanitation has to be managed precisely. With SIT, the radiation requires even more capital and controls.

Environmentally friendly farming methods have become a strong economic force. They are driven by the pressure from export markets to move away from chemicals. Fruit imported into first-world markets are scanned for the residues of unregistered or banned chemicals. The list of these chemicals is growing. Another factor is the increasing resistance of the pests to chemicals. Increasing the concentration of poison and the frequency of spraying as well as using new chemicals are expensive measures that only work for a while anyway.

The varied methods of integrated pest management seem to be the answer, and farmers are adopting them fast. But when the chemicals are cheaper,it is hard to convince a cash-strapped farmer to think medium-term rather than short-term. Another impediment to faster acceptance of IPM methods is the problem of their unproven credibility in the minds of many farmers. If you have your life savings tied up in the next harvest, as farmers continually do, the temptation to reach for the tried and tested can of poison is too much. Experimenting with integrated methods is simply postponed to better years.

The result of all these factors is a limited but growing application of bio-friendly pest control. Much education of the public will be needed to make it viable. Release times and methods require knowledge of the insects, as does the monitoring of their efficiency. The prize is unprecedented access to export markets.