The Paddy Gall-fly or Rice Stem Gall Midge (Orseolia oryzae Wood-Mason)

 

The Paddy Gall-fly or Rice Stem Gall Midge (Orseolia oryzae Wood-Mason)

Scientific Name:

    Orseolia oryzae Wood-Mason or Pachydiplosis oryzae W.M.

Order:

    Diptera

Family:

    Cecidomyiidae

Distribution:

    India, Bangladesh, Burma, Cambodia, Sri Lanka, China, Indonesia, Nigeria Northern Cameroons, Sudan, Thailand, Vietnam, Pakistan, South-east Asia and Africa

Host:

    Rice, wild species of Oryzae and grasses.

    The larvae are 1 mm long on hatching, with a pointed end and a pale colour. They eventually grow to 3 mm long and become red. The adult fly is yellowish brown mosquito-like and is 3-3.5 mm long.

Life-cycle:

    Copulation takes place soon after the emergence of the adult midge form galls on the rice plant and mating lasts for about 5 minutes. Oviposition starts a few hours later. The females mate only once and unmated females lay sterile eggs. The tiny pink fly lays reddish elongated egg either singly or in groups of 3 to 4 on the leaf or on stem and upto 250 eggs are laid by a single female. The incubation period is 1-3 days during August to November. On hatching, the tiny maggots crawl down to the base of the shoot and enter in a young plant where they feed until they pupate. The average larval period is 10-13 days. The pupa is adorned with a series of sub-equal spines which are pointed backwards. These spines enable the pupa to wriggle their way to the tip of the gall and cut a hole at the top of the gall from which the fly emerges after 4-7 days. The total life-cycle is completed in 15-23 days. There are 5-8 overlapping generations in a year and 3-5 generations on the rice crop.

Damage:

    The maggots enter the stem and reach the apical point of central shoot or tillers where they develop. Either the direct feeding by the maggot in the developing primordium or its secretion of some compound stimulates the growth of leaf sheath around the larva into an oval chamber which grows into a long tubular gall. The gall is commonly called 'silver shoot' or 'onion leaf'. After the emergence of adult midge, the gall dries up and disintegrates. The damaged tiller transformed into galls do not bear panicles. Early infestation results in profuse tillering of the plants but most of these new tillers also become infested. The galls can be easily detected in the field.

    Losses. In case of severe infestation, the losses upto 50 per cent have been reported.

Control:

    Spray chlorpyriphos 20 EC @ 625 ml or quinalphos 25 EC @ 500 ml or fenitrothion 50 EC @ 500 ml, in 750-1000 liters of water/ha, after 20-25 days of planting.

or

Apply granules of diazinon 5% or endosulfan 4%or carbofuran 3%,@,25 kg/n in the standing crop.