Pest control using bacteria and fungi
Biological insect control is currently the most important branch of biological pest control. The oldest and most widespread process is the use of the bacterium Bacillus thuringensis (Bt), with the first commercial product available in 1938. Now there are a variety of different strains which can be used specifically against pests of different insect families. One key application beyond plant protection is the use of Bt. israelensis against mosquitoes, especially to control malaria.
Besides bacteria, insect-pathogenic fungi are also used to control insects. The fungal spores remain adhered to the insects' skin forming germ tubes which grow into the insect. The insect dies within a few weeks and the fungus grows through it. Finally, millions of spores form on the surface of the dead insect, which in turn can be transferred to other insects. To give an example, grasshoppers in Africa and Australia are being controlled successfully using fungal spores (Green Muscle®).
Predator and parasitoid insects, mites and threadworms
Ever since bees have been used to pollinate tomatoes, peppers and aubergines in the mid 1980s, non-chemical insecticides had to be used in order not to affect the bees' valuable work. Now, the majority of greenhouse operators have switched to using biological means to control insect pests. The benefit for the health of the employees, the look of the plants and the maintenance of self-regulating mechanisms in these special crops justifies the additional expenditure on the plant protection agent. The antagonists can also often establish themselves in the greenhouse, thereby ensuring the crops are protected for the entire season, whereas chemical preparations require repeated applications. Above all, insects and mites are used in the greenhouse to control pest insects. The list of insects and mites used in Germany comprises over 35 species.
Beneficial insects also include parasitoids. These insects do not kill their host immediately; rather they exploit them as a nutrient source for their offspring. They lay their eggs in the caterpillars, the young animals, or other insects' eggs. The young parasitoids then develop there and ultimately hatch out of the egg, the caterpillar or the chrysalis of the host insect, which is of a different species. The chalcid wasp of the genus Trichogramma is the most important of these parasitoids and is widely used in Europe to control the European corn worm. Chalcid wasps are minute but can be seen with the naked eye. It only take 10 insects per m² of corn field to control the corn worm. At only 0.4 mm, the tiny insects are also inconspicuous in the home and can be used to control grain and dried-fruit moths. Last but not least, nematodes are parasitoids. But as they are the main line of e-nema GmbH's business, we have devoted an entire section to them.
Sex pheromones and young sterile males
Finally, the decimation of insects by preventing mating is also a biological process. This is carried out through the use of sources of pheromones which confuse the young males. The pheromones, which have no side effects, are used in many areas including viniculture against the grape berry moth and in apple growing against the codling moth. In concerted programmes to reduce pests or even to exterminate pests that have been introduced from elsewhere, in some areas sterilised young males are released in mass numbers. The method works well with insects that only mate once. It was used for the first time in 1950 to exterminate flesh flies on cows. Today, this technique is used on insects including the Mediterranean fruit fly and the mosquito as transmitters of malaria.