Papaya Fruit Fly
Females lay several eggs into very young or young fruits. The punctured skin exudes drops of latex that clearly contrast with dark green fruit coats. The larvae hatch and dig tunnels through the pulp to reach the seed cavity and feed on the developing seeds. Exit holes are clearly visible on the fruit surface. The extensive tunneling results in rotting of the flesh, reflected as brown and sometimes black lesions as it progressively decays. Fruits subsequently give off a foul odor and may ooze a juice-like substance. The skin turns yellow and may appear scabbed or pitted. The fruits ripen and can drop off prematurely.
The symptoms are caused by the fly Toxotrypana curvicauda that lays its eggs into small green papaya fruits. Adults are commonly mistaken for wasps because of their size, color, and behavior. They have a yellowish body with black marks symmetrically placed on the thorax. Females have a long, narrow abdomen with a extended curved egg-laying organ that exceeds the length of the body. Larvae are white and slender, about 13-15 mm in length. Fruits may be infested with several larvae each and show symptoms post-harvest. Fruit damage is highest after the rainy season is over. The papaya fruit fly is a major pest in the the tropical and subtropical areas of the American continent.
The parasitic wasp Doryctobracon toxotrypanae may have potential for control.
Always consider an integrated approach with preventive measures together with biological treatments if available. No insecticide seems to be effective against this fly. Traps containing an insecticide (e.g. malathion or deltamethrin) combined with a specific bait (for males or females) are being tested. Fruits can be treated with hot vapors of ethylene bromide to kill the papaya fruit fly.