Mango Blister Midge
The leaves, buds, inflorescences and young fruits of mango trees infested by the midge are covered by many small, raised blisters. Each wart-like blister is 3-4 mm in size and contains a yellow P. mangiferae larva which feeds on tree tissue. Heavily affected leaves may deform, show reduced photosynthesis, and drop prematurely. Infested inflorescences may be unable to open. Small exit holes on the underside of leaves are remnants of the presence of the larvae. These exit lesions may result in secondary fungal infections. Young fruits may also display exit holes at the base of the stem. In severely infected mango trees the shoots have almost no inflorescence. This considerably reduces the yield.
The adult mango blister midge is 1-2 mm in size, and dies within 24 hours of emergence after copulation and egg deposition. Eggs are laid on almost all tree parts. When they hatch, the larvae penetrate the tissues and inflict more or less severe damage depending on the organ they affect. Floral parts which are fed upon can consequently dry up and fall to the ground. Mature larvae migrate or fall onto the upper soil layers, where they enter the pupal stage. Emergence of adults usually takes place in the afternoon and is favored by cool temperatures (20°C) and 60-82% relative humidity. There can be up to 3-4 pest generations over the period of January-March in the northern hemisphere.
The fallwebworm (Tetrastichus sp.) can be used to control the pest. It parasitizes on the larvae of P. mangiferae.
Always consider an integrated approach with preventive measures together with biological treatments if available. Spraying of 0.05% fenetrothion, 0.045% dimethoate or 0.04% diazinon at the bud burst stage of the inflorescence can be effective in controlling the pest. Foliar application of bifenthrin (70ml/100l) mixed with water has also given satisfactory results. The spraying should be repeated at 7-10 days intervals in the flowering season until the fruits reach pea size. Sprays containing dimethoate, phosphamidon or monocrotophos have also been used to reduce P. mangiferae populations.