Alternative methods of insect control

There is a great deal of interest in several alternatives to traditional chemical insecticides, and much research and development work is being carried out on these by major agrochemical companies. Examples which we will briefly consider are (i) release of sterilized males, (ii) biological predators, (iii) microbial insecticides, (iv) pheromones and (v) growth-regulating hormones. 

1 Release of sterilized males. In this method very large numbers of, say, the male of the pest insect species are bred and are then sterilized by exposure to X- or 7-radiation. They are then introduced into the problem area in such numbers that there are far more of them than there are natural, fertile males, so that mating is much more likely to involve a sterile insect. As a result no offspring will be produced. Thus in time the population will decline and insects will no longer be a pest. 

Although the drawbacks are obvious—the vast numbers needed and the slowness of the processes—the method has clear advantages in that it is highly specific and will not create any adverse environmental effects. It was extremely successful in the eradication of the screw-worm from Curacao. This, however, was a rather special situation involving an island. A similar campaign in the south-western United States involving release of 4 billion sterilized male screw-worms was only partly successful. 

An alternative approach is to use chemosterilants, i.e. chemicals which sterilize, directly on the natural population of insects. One such compound is Apholate. 

2 Biological predators. This method consists of releasing a biological predator to control the insect pest. In the United Kingdom its only successes have been in enclosed environments such as glasshouses. However, the technique was used very successfully nearly 100 years ago in California when the Australian ladybird beetle was introduced as a predator for cottony cushion scale which was ravaging citrus trees. 

---