Large-scale confirmatory tests of a phytosanitary irradiation treatment against Sternochetus frigidus (Coleoptera: Curculionidae) in Philippine mango.

The mango pulp weevil, Sternochetus frigidus (F.), is an important quarantine pest preventing the export of mangoes from the Philippines to the United States and other countries. Previously, a radiation dose of 100 Gy was proposed for phytosanitary treatment of S. frigidus based on dose-response studies with larvae, pupae, and adult weevils. To validate an irradiation treatment, large-scale confirmatory tests were conducted with adults (the most radiation-tolerant stage) in mangoes at 100 and 150 Gy. After treatment, adults were removed from fruit, sexed, and mated in pairs to observe any reproduction. At 100 Gy, adults laid a small number of eggs but none of the eggs hatched. At 150 Gy (measured doses 96.7-164.1 Gy),4,559 treated weevils laid no eggs, indicating that this dose caused complete sterility. Irradiation treatment with a minimum absorbed dose of 165 Gy will therefore provide quarantine security for S. frigidus in exported Philippine mangoes.