Two major limiting factors in rice cultivation are adverse weather and pest epidemics. Yield loss due to insect pest attack in rice cultivation is considerably high. Among the pests attacking rice, leaf folder causes much damage between 30 and 60 days after transplanting.
Before the introduction of high yielding and nitrogenous responsive varieties this pest was sporadic in most of the rice growing tracts.
With the expansion in rice area due to modern agricultural practices, high yielding varieties and indiscriminate use of nitrogenous fertilizers the pest has now attained major status. Cloudy weather with low sunlight favours pest build-up.
In case of severe infestation, the leaf margins and tips became dry and crop gives a whitish appearance. The damage is more conspicuous during active tillering to booting stage. Flat oval yellowish eggs are laid singly or in pairs on the under surface of tender leaves. The eggs hatch within 4 to 7 days.
Larvae are yellowish green with dark brown heads and turn into actively moving caterpillars. They pupate in loosely woven silk threads inside the leaf roll. Adult moth emerges in 6 to 8 days. It is yellowish brown with several dark wavy lines on the wings.
Split the fertilizer application during the growing season and apply nitrogenous fertilizer judiciously.
Remove grassy weeds to prevent the buildup of rice leaf folders which act as the alternative hosts.
Release the egg parasitoid Trichogramma chilonis at 5 cc/ha on 37, 41 and 51 days after transplanting.
Spray any one of the following insecticides: cartap hydrochloride 50 per cent SP at 2 gm/lit or profenofos 50 EC at 1.5 ml/lit or chlorpyrifos 20 per cent EC at 2 ml/lit or indoxacarb 15.8 EC at 0.7 ml/lit or azadirachtin 10,000 ppm at 2 ml/lit of water. Add sticking agent at 1 ml per litre of water.
Avoid excess application of carbofuran and phorate as far as possible as these will result in resurgence of the pest.
(Dr. J. Ramkumar, Assistant Professor (Agrl. Entomology) and Dr. R. Durai Singh ,Programme Coordinator, KVK, Tamil Nadu Agricultural University, Ramanathapuram - 623 503, E.mail: email@example.com ; Ph. No: 04567-232639.)