Natural enemies of rice leaf folder Cnaphalocrocis medinalis (Guenée) —a critical review

A chronological review of the biological control agents of rice leaf folder, Cnaphafalocrocis medinalis Guenée, including the stage of host attacked in different countries, their activity and suggestions for future. The rice leaf folder, Cnaphalocrocis medinalis Guenée, which was a pest of minor importance till the last decade, recently has assumed major importance in many rice ecosystem of Asia, the South Pacific Islands, Hawaii and Australia (Hirao, 1982). Increasingly frequent outbreaks of this pest (Table I) in recent years have been attributed to the introduction of modern rice technologies, namely: Continuous and overlapping cropping (Rajamma and Das, 1969); introduction of broad leaf dwarf, high tillering. fertilizer responsive susceptible rice varieties (Gargav and Katiyar, 1971; Dorge et al., 1972; Patel, 1975) and increased use of nitrogenous fertilizers (Michael Raj and Morachan, 1973; Chandragiri et al., 1974; Subraiah and Morachan, 1974; Dhaliwal et al., 1979; Chantaraprapha el al., 1980; Miynhara, 1981). In addition shading which causes the rice plants to grow tall with reduced silica content may make plants more susceptible (Chelliah, 1983). However, no detailed information is available as to how these factors bring about favourable conditions for larval growth and survival and or cause enhanced fecundity of the adults.