INTRODUCTION TO BIOLOGICAL CONTROL

Two basic types of biological control agents are available: predators and parasitoids (parasitic wasps). In general, predators attack a larger range of potential prey species, kill them a soon as they find them, and leave no trace of the prey's remains. In many cases (e.g. minute pirate bugs (Orius species)), both adult and immature stages of the predator may kill the target pest(s). In other cases (e.g. the green lacewing (Chrysoperla rufilabris) and the predatory midges Aphidoletes and Feltiella, the larva is the predatory stage.

Parasitoids behave differently. Adult parasitoids typically feed on floral nectar or similar sources of sugars (e.g. the 'honeydew' secreted by sucking insects such as aphids). The females of some parasitoid species also engage in 'host feeding', where the body of the host insect is punctured by the female wasp, who then feeds on the body fluids that seep from the wound (the wounded host typically dies as a result). However, in most cases, it is the larval stage of the parasitoid that kills the host insect. The adult female wasp lays one or more eggs in a suitable host, and when the wasp larva hatches, it gradually consumes the host's internal tissues, eventually killing it. At that point (which may take several days), the parasitoid larva pupates (either inside the dead host or on its surface, depending on species), and eventually emerges as a new adult that repeats the process.

Since parasitoid larvae must overcome the host's internal immune system, they tend to be more restricted in the number of pest species that they can successfully attack and kill. For this reason, correctly identifying the target pest is always important, but especially so when selecting an appropriate parasitoid to use.

Both types of biological control agent can be effective, but ALL need to be released into the crop as soon as the pest is first detected. Regular, effective pest monitoring and prompt release of appropriate natural enemies are both necessary for successful biological control!

Each species of biological control agent grows, survives and thrives at a particular range of temperatures, humidities and daylength. These are described in the individual product selection pages for each group of target pests, but to make comparisons a little easier for you, we have summarized this information for all our species into two downloadable tables (below): one in Fahrenheit (°F ) and one in Celsius (°C). Please note that each species will function under conditions slightly outside their optimal range, but at a somewhat reduced level of performance.