Chapter 5 - Trichogrammatids

Abstract

Among the various egg parasitoids that are known to exert considerable pressure on populations of insect pests, Trichogramma species are the most widely exploited and used for pest management across the world. There are 230 recorded species and the highest numbers of species have been described from the USA, India, Brazil, China, and Russia. Some of the important species that have been recorded from several insect eggs include Trichogramma minutum, Trichogramma evanescens, Trichogramma chilonis, Trichogramma pretiosum, and Trichogramma dendrolimi. At least four species have been recorded from over 50 host plant species: T. chilonis and T. pretiosum from 70 host plants each, T. minutum from 53 plants, and Trichogramma deion from 51 plants. Thus these are species that have been the most exploited for biological and integrated control of crop pests. Work on the molecular characterization of more than 30 species of Trichogramma has been carried out in India and is reported here. Considerable information on the effect of plant extracts, synomones, temperature, and insecticides on trichogrammatids has helped in their utility in pest management and is covered in this chapter. Work on genetic improvement of various Trichogramma species has led to the development of insecticide-tolerant strains that have been extensively utilized in the field on crops that are subjected to intense pesticide pressure and development of high temperature-tolerant strains and their evaluation in the hotter months has shown the usefulness of such strains, particularly on pests of sugar cane. Information on the management of various insect pests on 18 crops using Trichogramma species has indicated that these could either be used as alternatives to chemical pesticides or as an important component in the integrated management of pests on several crops.