Field Evaluation of Insecticides for Asian Corn Borer on Vegetable Corn, Pangasinan, Philippines, 1979

Early maturing corn (55 days) is grown with the onset of the monsoon rainy season as a cash crop by small-scale farmers before puddled rice. Corn borer infestations begin as early as 21 days after crop emergence (DE), thus insecticide sprays were applied on 21, 31, and 41 DE and granulars were applied once by hand in the whorl on 21 DE. Five trials on farmers' fields evaluated 31 insecticides. Azodrin was included in each trial for comparison. Insecticides were applied at 1.0 kg ai/ha to 4 replicated plots (50 sq m) by a manually operated, 19-1 knapsack sprayer with a fan jet nozzle in a randomized complete block design. Spray volume averaged 650 l/ha. Corn (2-4 seeds/hill, 50-cm between hills) was planted by hand in furrows 1-m wide and received no fertilizer application. Rainfall was 37 mm (Apr), 305 mm (May), and 144 mm (June); RH averaged 77%; and the mean daily maximum and minimum temperatures were 35° and 23 ° C, respectively, during the crop period. At harvest 25 plants/plot were examined and cut open to record the number of corn borer cavities and larvae (inside and outside the stems). Yield was based on 20-sq m. The ears were sorted by length to select those which were marketable (10 cm). Insect damaged ears are marketable to the local consumers.