Fatal attraction
Rather than pit insect predator against insect prey, the Lethal Insect Technique uses biological control in an entirely different way. Sinister though it sounds, the pest insects themselves destroy their fellows by passing on the microbiological disease with which they have been deliberately contaminated.
Although, in theory, applicable to any pest that is controlled by the mass rearing, sterilization and release of infertile males, (Sterile Insect Technique), it is tsetse flies, a major problem in much of Africa, that are currently being targeted for control by this much cheaper method, the Lethal Insect Technique. It is an idea supported by the Austrian government through its Austrian Development Cooperation and promoted by ICIPE, the International Centre of Insect Physiology and Ecology, with headquarters in Nairobi, Kenya.
The basic principle is quite straightforward. Tsetse flies are reared in 'fly factories' or insectaries and before release to the wild they are contaminated with a lethal, insect specific fungal disease which will eventually kill them - but not before they have had time to spread the disease to wild flies they have contacted. At carefully located permanent release sites, small boxes, which are supported off the ground by bamboo poles, serve to contain the reared pupae from which the male and female flies are ready to emerge. These pupae are covered with a mixture of sand and fungal spores. During the emergence process, the flies become contaminated and are fated to die within about a week to ten days.
For the first few days the contaminated flies behave normally, and their normal inclination is to find a mate. But it is a fatal attraction. The disease is passed from fly to fly by simple body contact. This is one of the great advantages over the Sterile Insect Technique which demands, consumated mating to achieve the desired objective - that the mated female be unable to produce the next generation of offspring.
Another advantage is that, whether a male contaminated fly seeks a wild female, or a female contaminated fly is sought by a wild male, the result is the same - sickness and death. This means that both male and female flies can be used in the Lethal Insect Technique whereas in the Sterile Insect Technique expensive gender selection has to be undertaken in order to give the sterilized males a more than even chance with the wild population of females.
The same principle can be used in a more conventional trap system. Instead of allowing trapped tsetse flies to die within the trap, they are allowed to escape, but not before passing through the microbiological contamination that will ultimately ensure certain death.
