Influence of Bt-corn variety yieldgard on the effectiveness of trichogramma evanescense (hymenoptera:trichogram matidae), and egg parasitoid of the asian corn borer, ostrinia furnacalis (Guenee)

The study was conducted in Isabela State Unversity during the dry season and in the farmers' field in Barangay [village] Sumabaran, Echague, Isabela are Barangay Villaluna, Cauayan, Isabela during the wet season cropping. Significantly more asian corn borer (ACB) egg masses were recorded on bt-corn variety yieldgard than on its Isohybrid during the dry season cropping. Although no trichogramma parasitoids were released in the field, egg mass parasitism range from 35 to 50% at 30 days after planting (DAP), and increased to 100% at 53 DAP in both the yieldgard and isohybris varieties. The populations of flower bug (Arius tantillus), coccinellid beetle, and spiders were also higher on yieldgard than on the isohybrid. No ACB damage was recorded on yieldgard. Ispite of the very high egg mass population recorded, the isohybrid was almost totally free from ACB damage prior to harvesting due to high natural enemy populatio. As a result, yield of yieldg ard did not differ significantly from that of the Isohybrid. Low rate of trichogramma parasitism was recorded in the two barangays in Isabela during the wet season cropping. Likewise, the predator population (arius, coccinellid beetles and spiders) was negligible. Although fewer egg masses were recorded during the wet season cropping, ACB damage was significantly higher on the isohybrid variety. Cosequently, significantly higher yield was recorded for yieldgard, in both locations, with more than 5 tons yield advantage over the Isohybrid. The very high Trichogramma parasitism and high predator population in variety yieldgard during the dry season cropping suggested that Bt-corn is not deterious to the natural enemies. These natural enemies could hup in delaying ACB resistance development in Bt-corn by controlling the pest at the egg and early larval stages to reduce emerging Bt-resistant adults.