There are various strategies of allelopathic interactions, which help in reducing population of plant pests, the most popular being the ‘Botanical Pesticides’. Such plant allelochemicals possessing pesticidal properties constitute a transition bridge between synthetic pesticides on one hand and totally natural pest control on the other. This aspect of allelopathy can be exploited in different ways:
A large number of tropical plants, having pest control properties have been studied and in a few cases the biologically active groups or principles have been commercialised. Neem (Azadirachta indica) is by far the best known and documented, with over 200 commercial products in the world market.
The leaves, possessing pesticidal and/or pest repelling activity can be added to soil to control harmful soil insects, nematodes and other pests. Similarly fresh or dried leaves can be added to grain and other harvested produce for safe and effective postharvest protection.
Appropriately designed mixed cropping systems, can help in decreasing pest damage through allelopathic effects. The allelopathic interactions between the main crop and an intercrop and their respective pest complexes keep certain pest species away from the main crop, either by acting as repellents or as attractants towards the intercrop (which is then said to act as a ‘trap crop’).
Another aspect of allelopathy involves insect-host plant relationships through semiochemical-mediated interactions. Allomones and kairomones play an important role in host recognition, host selection and host colonisation by insects, and have implications in insect pest management as well as in crop production.