Successful control significantly reduces pest infestation. However, this also means the natural enemies are left without food. The crucial question is: where have they gone?
Most natural enemies really need their favorite pest to survive. When it is no longer present, they fly or walk around in search of new food. If they don't find it, they will eventually die. Biological beneficials generally have a short life span. So they just disappear.
How quickly this happens varies by species. Parasitic wasps are fragile and often only live a few weeks. However, some species of predatory mites can survive for quite a while without food, as long as several weeks. And some species of mites can even go into a sort of hibernation, but in most cases we've selected them not to do that. After all, they were ‘hired’ to work.
The rapid disappearance of useful insects is sometimes a disadvantage – especially if your intention is to build up a standing army of useful insects or mites in the crop before the pest arrives. This is absolutely essential for pests that develop at lightning speed.
This strategy can be used for predatory bugs and predatory mites. These types of natural enemies can survive on pollen, for example. But without their protein-rich snacks, their development is much slower than when they have an unlimited supply of their favorite prey. In the case of predatory bugs used against whitefly, the difference can be as much as a factor of ten! To stimulate the development of predatory bugs and mites, we feed them with prey mites or moth eggs (Entofood). This is essential, as the population would otherwise decline over time. The use of banker plants is also a proven method of maintaining the population.
To better understand how to keep your standing army, standing, contact a local Koppert consultant for the best strategy.