Mango Gall Midge
Predominantly the leaves, but occasionally also the buds, inflorescences and young fruits of mango trees infested by this midge become covered with many small, raised black galls. Each gall is 3-4 mm in size and contains a yellow larva which feeds on tree tissue. In early stages, the site of egg deposition appears as a small red spot. Heavily affected leaves may deform, show reduced photosynthesis, and drop prematurely. Infested inflorescences may be unable to open. The small exit holes visible 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. Severely infected mango tree shoots have almost no inflorescence. This considerably reduces the yield.
The adult mango gall midge is 1-2 mm in size. It dies within 24 hours of emergence after copulation and egg deposition. Eggs can be laid on almost all tree parts but they are predominantly found on leaves. When they hatch, the larvae penetrate the tissues and inflict more or less damage depending on the organ they affect. Floral parts, for example, can dry up and fall to the ground due to extensive feeding. 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. pustulata.
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 also works. Repeat the spraying at 7-10 days intervals in the flowering season until the fruits reach pea size. Alternatively, sprays containing dimethoate, phosphamidon or monocrotophos help reducing P. pustulata populations.