Sunhemp damage by defoliator

SUNHEMP (Crotalaria juncea) is generally grown in Tamil Nadu, Andhra, Karnataka and northern states as a green manure crop to enrich the soil fertility. It is grown prior to the planting of the paddy crop i.e., before 30-40 days and ploughed. The sunnhemp crop with thick foliage adds organic matter to the fields. The nutrient "N" content in the leaves found to be very high. The leaf defoliator-cum-podborer, Uthesia pulchella assumes pest form at certain times. This causes defoliation of the leaves and yield loss in crop meant for seeds at times if it is not checked.

The defoliator is a caterpillar measuring about 2.0 cm in length, feeds on the leaves in the early stages of the crop. Four to five caterpillars are found in one twig of the tender plant consuming the entire leaf and also the inflorecence. The damage is also seen during pod formation. It bores into pods and feeds on the seed materials inside. Number of moths can be seen flying in the fields when there is an outbreak.

The eggs are white in colour and singly laid on the margins of leaves. They hatch in 3-5 days and the hatched larvae food on the tender leaves.

The full grown caterpillar has a brown head and yellow line on the back sides with black stripes and orange patches on the sides. It has long brownish hairs on the body and moves quickly. Larval period lasts for 20-25 days. It pupates in leaf folds or in the soil and the pupal period lasts for 7-10 days. The moth is white with red and black spots. This is a specific pest of this crop.The pest can be effectively managed by: Moths are attracted to high intensity light sources, set up light traps to monitor the pest, to assess the damage and kill them.

Spraying of fenthion 100 E.C. at the rate of 1.0 ml or monocrotopohs 36 WSC at 2.0 ml/ litre of water will reduce the infestation.

M. Meerzainudeen

N.Raju, S. Sadakathulla

TRRI, Aduthurai 612 101.

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