Ovipositional preference of Trichogramma dendrolimi and Trichogramma ostriniae strains from Myanmar on different host egg ages of Asian corn borer, Ostrinia furnacalis (Lepidoptera: Crambidae)

Abstract

ABSTRACT Trichogramma (Hymenoptera: Trichogrammatidae) wasps are the most successfully biological control agents against the Asian corn borer, Ostrinia furnacalis (Guenée). To progress with biological control of this pest in Myanmar, we investigated the performances of three strains of T. ostriniae and two strains of T. dendrolimi on O. furnacalis eggs of different ages (6–12-, 12–24-, 24–36- and 36–48-hr) under choice and no-choice conditions. The ovipositional preference was significantly different among these tested strains. Two T. dendrolimi strains from Southern Shan State of Myanmar and China exhibited a strong preference on the younger, 6–12-hr-old host eggs. The two indigenous T. ostriniae strains showed no difference in ovipositional preference for the first three ages (6–12-, 12–24- and 24–36-hr), however, the preference of T. ostriniae from China was significantly higher on the 12–24-hr-old eggs. None of the strains tested strongly preferred the 36–48-hr-old eggs. Under no-choice conditions, all tested ages were accepted by all Trichogramma strains, however, the T. dendrolimi strains parasitised significantly fewer eggs with increasing host age. Wasp emergence rate was also higher (94%) from the 12–24-hr-old eggs while immature developmental time was significantly prolonged on the 6–12-hr-old eggs. Two T. ostriniae strains from Southern Shan State had a broader host age preference with higher parasitism, being 32 eggs/female, and produced a greater number of progeny (∼43). These two T. ostriniae strains were identified as the most effective Trichogramma strains of O. furnacalis. The present study provides valuable information for a potential biological control programme of this maize key pest in Myanmar.