The use of insects in the greenhouse

Cultivation

A natural enemy can be found for every harmful tomato plague. It is most important that the cure is distributed at the right time, and in the right numbers. There are a few mechanical aids: yellow, blue, or orange sticky traps. The following plagues occur in the order of highest to lowest frequency.

Whitefly

The nr. 1 plague also often occurs in nettle and geranium. The Whitefly lies its eggs on the underside of the leave, and they can completely destroy a plant in 2-3 months if left untreated. It can, however, be very well treated biologically by using ichneumon wasps and assassin bugs. The ichneumon wasps are already used weekly at the start of the cultivation. They drill a hole in the egg of the Whitefly and replace it with their own. When this happens, the egg turns black, and the grower can see if parasitism occurred. The white/black ratio of the eggs has to be around 50/50. The assassin bugs eat the eggs whole, and prefer those of the Whitefly. They will, however, eat other enemies as well. Only a few thousand assassin bugs are used, since they are relatively expensive (about 20 cents each).

Caterpillars

For this plague there are also many biological cures. Not only assassin bugs, but also the great tit and the white wagtail eat a large part of the caterpillars. Hanging nest boxes is not only a way to attract birds to the greenhouse, it is also a way to ensure they come back each year. In case there is an exceptional large amount in the greenhouse, caterpillars can also be treated with bacteria. The plague can therefore be cured completely biologically.

Leafminer Flies

This fly makes little holes in the leaves, and can turn an entire plant from green to white. To cure this plague it is necessary to deploy many ichneumon wasps. This relies completely on the time of the year.

Red Spider Mite

Red spider mite are very small spiders that make a delicate web and can suck a plant completely dry, in which case the plant will die. The cure for this plague is by using a predatory mite, which attack and eat the red spider mite. It is very important to place the predatory mite early on, and in large numbers on a lot of plants.

Lice

Lice do not occur on tomato plants often, but they can be easily be done away with by using ichneumon wasps.

To this extent the bugs a tomato grower has to deal with.

Fungi

Mildew

These are snow-like flakes that can destroy an entire crop in a matter of weeks. It is very treatable by evaporating sulphur in the greenhouse for a few hours each day. This method is often used in the biological world as well, and is completely harmless to humans.