Introduction

Large-scale movement of vegetable, fruit, and ornamental plants between nations entails the danger of accidental introduction of insect pests, nematodes, plant pathogens, and weeds. The problems due to accidental introduction of weeds are manifold. A pest organism or weed, thus introduced, finds the new habitat conducive for breeding and establishment without any regulation by the natural enemies that would have kept the introduced species under check in their original ranges. Dominance of the invasive species in the new habitat causes immense damage to the native fauna and flora, thus upsetting the natural balance within the new habitat. Conventional methods of weed control are difficult for such invasive weeds and the use of chemical herbicides in uncultivated areas generally is uneconomical and can have ill effects on nontarget organisms.

An ideal way of managing invasive species, whether insects, mites or weeds, would be to introduce and establish effective natural enemies from their native home range. Biological weed control involves the deliberate use of natural enemies (e.g. plant-feeding and disease-causing organisms) to reduce the densities of weeds to economically or aesthetically tolerable limits, which need not necessarily lead to complete eradication. This chapter has been written to supplement the information of the review by Sankaran (1973) and Jayanth (2000).