Natural enemy components of Asian corn borer, Ostrinia furnacalis (Guene) with emphasis on mass rearing technique field performance and selectivity to insecticides of predatory earwig, Euborellia annulata (Fabricius)

The most predominant and most promising natural enemies of the Asian corn borer at CES, UPLB [Central Experiment Station, University of the Philippines at Los Banos, College] were the anthocorid bug (Orius tantillus), the earwigs (Euborellia annulata, E. philippinensis, Labidura riparia, Proreus simulans and Nala lividepes) and Trichogramma parasites. The abundance of Orius coincides with the abundance of the corn borer egg mass deposition while the natural population of earwig increased prior to harvest. The Trichogramma species were observed to parasitize about 90% of corn borer egg masses even in the absence of previous mass releases. The predominant natural enemies encountered at Villaverde, Nueva Vizcaya [Philippines] were Trichogramma species, coecinellid beetles, anthocorid, mirid and reduviid bugs. No natural enemies were encountered in Soliven, Isabela. The earwig, Proreus simulans was very abundant in the cornfields of the University of Southern Mindanao. The earwigs usually underwent four nymphae instars when reared on larvae/pupae of red flour beetle and the total developmental period ranged from 35 - 45 days. A maximum of six egg batches were laid by a female. The female earwigs brooded their eggs and cared for the nymphs. A mass rearing technique was developed for E. annulata which could also be employed for the other species of predatory earwigs. The anthocorid bug completed its life cycle in 16.5 days on the average using rice moth eggs and first instar larvae as its unnatural host. The mass rearing technique for Orius needs further refinement. The release of 9,167 earwigs per hectare per release at 35 and 45 days after planting reduced corn borer damage and gave yield comparable to calendar spraying with insecticide. The anthocorid bug could also significantly suppress population increase in the corn borer. Among the insecticides evaluated against the corn borer, carbofuran and cypermethrin are selective to E. annulata. If the use of biological control agents like Trichogramma parasites, anthocorid bugs and earwigs will be aggressively persued, the disruptive effects of pesticides could be avoided