Author : Sieng Klitsaneephaiboon

Summary : The effects of detasseling and stalk removal above the ear of corn plants, tassel ratio index, parasitism on plant at maturity and pollen application to the leaf axils above the ear, were studied for population regulation and infestation of the Asian Corn borer, O. furnacalis, during the wet and dry seasons, from 1982 to 1983. Dry season planting had more rapid rate of plant development, higher tassel bud ratio, and earlier tasseling and silking than the wet season. There was no difference in adult oviposition between untreated and treated plants. Counts of egg masses increased at vegetative stage and decreased at the reproductive stage of plants in both seasons. At tassel emergence, larval population collected from the tassel in both seasons was greatly higher than larval population collected from other plant parts. Association and relationship of the number of larvae and tunnels above the ear, at the ear and shank, and below the ear were high but very low at the tassel. Larval population recorded from the tassel at silk emergence was much lower than that at tassel emergence, but the number of pupae, and tunnels were slightly higher. Stalk removal at dough stage showed greater number of larvae, pupae, and tunnels than stalk removal at beginning dent and fully dented stages. In the absence of chemicals, detasseling before pollination showed the greatest reduction in the number of pupae and tunnels above the ear compared to detasseling after pollination and intact plants with tassel. At harvest, tasseling before pollination even without insecticide treatment reduced the number of tunnels in different plant parts, equal to the result of detasseling after pollination or intact plants with tassels and insecticide treatment.