Adult rice gall midges are tiny, night active flies that look like small mosquitoes (Fig 1). They are usually about 3 mm long. The larva has no legs, is flat to cylindrical in shape, and tapered at both ends with whitish/yellowish colour.

Damage symptoms

The larvae feed inside of tillers where they cause the plant to form a gall, meaning that the tiller diameter is much increased to provide extra nutrients and space for the growing larvae (Fig 2). The gall may reach 1 cm in diameter and 30 cm length to support development of many gall midge larvae. Affected tillers inhibit growth of leaves, fail to produce panicles and the plant is stunting (Fig 3).

Control options

The population density of the Asian rice gall midge is favored mainly by cloudy or rainy weather and is thus mostly problematic in monsoon rice. High-tillering varieties and intensive management practices, favour development.

Cultural control: sound plowing ratoons of the previous crop and removing all off-season plant hosts can reduce infestation. Crop rotation is highly recommended in areas suffering from gall midge to break the cycle of this pest. Resistant variety may be grown when available.

Biocontrol: several parasitoids are known to attack gall midges and thus every effort should be taken to preserve these natural enemies.

Chemical control: Due to its internal life style and protection through the gall, it is very difficult to control the gall midge with insecticides.