Microbial Control of Sucking Pests Using Entomopathogenic Fungi

Abstract

Sucking pests cause serious damage to several agricultural, horticultural and plantation crops either by direct feeding or by transmitting plant viral diseases. Since sucking pests likc plant and leaf hoppers, aphids, whiteflies, scale insects, thrips and mites to have developed resistance to insecticides, biological control using microbial pathogens, particularly funga1 pathogens like Beauveria bassiana, Metarhizium anisopliae , and Verticillium lecanil , has been explored for a number of pests. Several commercial formulations based on entomopathogenic fungi were developed for the control of sucking pests in different countries. Mycotrol and Botanigard based on B. bassiana, Mycotal based on V. lecanii and PFR-97 and Pae-Sin based on Paecilomyces fumosoroseus were developed for the control of whiteflies, aphids and thrips in USA, Europe and Brazil. In India, Fusarium pallidoroseum was found effective in controlling cowpea aphid ( Aphis craccivora ) in Kerala. Hirsllte thompsinii has been tried against the coconut eriophyid mite, but not found very promising. The wetland ecosystems like the rice fields as well as the sugarcane ecosystem have been found ideal for the use of M. anisopliae against sucking pests. M. anisopliae and B. bassiana were found to infect the sugarcane woolly aphid ( Ceratovacuna lanigera ) but these were also pathogenic to potential predators like Dipha aphidivoru and Micromus and hence cannot be recommended. Apart from these fungi, entomophthoralean fungi like Erynia neoaphidis, Neozygifes fresenii and Zoophthora radicans are reported to cause epizootics in several aphid species in nature. Fungal pathogens occur very widely in nature and there is a wide scope for isolating strains of fungal pathogens with enhanced virulence as well as desired cultural characteristics. Fungal formulations developed as microbial insecticides should possess good fluid stability and shelf life. Oil formulations have been found to be more effective against target pests even under low RH and aso possess a good shelf life. Since the muscardine fungi are pathogenic to beneficial insects like silk worms, honey bees, pollinators, as well as predators like coccinellids, utmost care should be exercised. Other pathogens like entomopathogenic nematodes (EPN) have been considered for the management of sucking pests but not with much success. The chance of acquisition of bacterial and viral pathogens into the gut of the sucking pests is limited and hence these pathogens have not been considered for the manllgement of sucking pests. Infectivity of protozoans to sucking pests has been rarely reported. The current status of microbial control of sucking pests and the future prospects are reviewed in this paper.