Arthropod profile and incidence of Asian Corn Borer, Ostrinia furnacalis (Guenee) (Lepidoptera:Pyralidae), in corn in Mambusao, Capiz [Philippines]

The study was conducted to: a) establish the profile of arthropods in corn agroecosystem in Manibad, Mambusao, Capiz; b) monitor the incidence of Asian corn borer in Bt corn and non-Bt corn (with and without insecticide) in the field; c) determine the extent of damage by the natural infestation of Asian corn borer; d) assess the population of selected natural enemies associated with the Asian corn borer; and e) determine the effect of ACB infestation on the yield of Bt and non-Bt corn and translate such effect in terms of cost and return analysis. Nine species of insect pests and 12 species of natural enemies including three species of spiders were recorded. Among the insect pests observed, five species are considered as defoliators and four species were sap suckers. The Asian corn borer was considered the important lepidopteran pest of non-Bt corn throughout the study based on the number of egg masses and larvae and the extent of damage they inflict on the plants in all growth stages. The highest number of ACB egg mass (0.26 per plant) was monitored during the late whorl stage (45 DAE) during the wet season cropping of 2005. The corn borer larvae were ob served only on non-Bt plants. While during the dry season cropping of 2009, there was negligible number of ACB larvae observed feeding on Bt plants. Foliar damage by ACB was slight to moderate in both croppings. At harvest, ACB damage in the form of tunnels in the stalk and corn ears were generally very low. Few ACB tunnels were observed only in non-Bt plants. During the 2009 dry season cropping, ACB larvae were observed feeding on Bt plants as well as in non-Bt corn plants specifically during the seedling, tasseling and silking stages. Few pupae were observed on non-Bt plants only. Low populations of lady bird beetle, Micraspis sp. was monitored during the mid-whorl stage in both Bt and non-Bt corn plants. The population increased at late whorl stage, reaching its peak at tasseling stage when the ACB larval population started also to reach its peak and the corn plants started to produce its inflorescence and pollen grains. Micraspis population was not affected by the different treatments in all the observation periods implying that Bt corn plants have no deleterious effects on the population of this natural enemy. The corn leafhopper (Dalbulus sp) was observed during the seedling stage until the tasseling stage of the corn. The lowest number of corn leafhoppers was observed from Bt corn plants. Yield among the treatments was not affected by the ACB infestation in both cropping seasons. A relatively highesr net profit was obtained from Bt corn during the 2009 dry season cropping due to the higher yield and prevailing price of corn per kilogram.