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Caterpillars are about 1.5mm long at first instar and reach a final length of 2.5mm. They are pink or brown and burrow into corn ears and stalks, damaging kernel production and causing stalks to collapse. Caterpillars generally remain concealed inside the plant, so are difficult to initially detect and access. Fully grown larva overwinter inside tunnels in corn stalks, or in wild plants.
Although chemical pesticides are applied to control O. nubilalis on capsicum and potatoes, chemical control is considered less effective for this pest on maize, because of the expense, the effect of the pesticides on beneficial species that help with control, and the difficulty of accessing the larvae inside the plant. Alternative control methods include release of commercially available parasitic Trichogramma wasps. The bacteria Bacillus thuringiensis subsp. kurstaki (Bt) can be successfully applied to target first stage larvae, and hybrid maize strains have been engineered to produce Bt toxins. Bt-corn however, has critics that worry about the effect of Bt on non-target species and also on producing Bt-tolerant strains of O. nubilalis. Maize hybrids created for tolerance to boring damage are also available and have helped minimize losses. Pheromonal control (using synthesized female sex pheromones to attract and trap males) proves difficult because the different moth strains are sensitive to different combinations of pheromone chemicals, but pheromone traps can be helpful in monitoring populations and timing of stages in the field.
(CABI, 2011; Capinera 2000)