Biological control is taking place in fruit crops whenever the existing populations of natural enemies are conserved. The impact of natural enemies is often underestimated but may become obvious if they are killed by broad-spectrum insecticides. However, they are not always sufficient to bring pests under economic control. The release of mass-reared beneficials can also aid in suppressing pests. This tends to be more successful in greenhouses than in the field, but there are now several instances where releases in the field have been proven to suppress, if not completely control, key pests.
For example, beneficial nematodes are very small roundworms attack soil-dwelling insects. Two in particular (Steinernema and Heterorhabditis) have been mass-reared for commercial use. These seek out and penetrate their host insects, multiply within the host and kill it. They are most likely to be effective against the soil-dwelling immature stages of susceptible hosts, such as root weevils, cutworms, white grubs, wireworms, and maggots. Nematodes require moist soil conditions to survive. Consult the Resources section in the appendices of this guide for sources of further information and suppliers of beneficial organisms.
