Controlling cotton stem weevil
COTTON STEM weevil, Pempherulus affinis, has of late been serious in all cotton growing districts of Tamil Nadu especially Coimbatore, Madurai, Periyar, Salem, Dharmapuri, Dindugal, Ramanathapuram and Nellai Kattabomman districts.
The adult weevil lays eggs on the tender cotyledon nodal region of the plant. The grubs feed inside the stem by causing fine spiral galleries and damages the tender vascular tissue.
Mostly they affect 15-25 days old plants. Feeding of the grubs dries the plants. Grown up plants develop woody gall at the collar.
These galls are the weak points where the stem breaks if there are strong winds or if disturbed during inter cultivation operations or due to very heavy boll formation.
The number of bolls per plant is considerably reduced and the lint quality is also very badly affected by the pest.
The weevil can be controlled by reducing the cropping intensity.
The soil around alternate hosts such as the Hibiscus spp, and the Abutilon spp should be treated with the chemical chlorpyriphos at 4 ml/litre of water as a soil drench at the collar region.
During cropping affected and dried plants should be destroyed.
After harvest, burning of the galled plants will reduce the weevil incidence during the next cropping season.
Sowing high seed rate/acre, removing and destroying the affected plants will help in maintaining plant population.
Neem seed cake can be applied at the rate of 100 Kg/acre at the time of land preparation.
The plants should be drenched with one per cent neem oil 15-20 days after germination (repeat at 15 days interval) and earth up to cover the cotyledon nodal region of the stem to prevent the egg laying of the adult weevils.
In the case of severe incidence, drench the plants with monocrotophos 2 ml/lit or chlorpyriphos 4 ml/lit of water at 15 days interval commencing from 15-20 days after germination.
B. Dhara Jothi, T. Surulivelu, & T.P. Rajendran
Central Institute for Cotton Research Regional Station,
Coimbatore-641 003, T.N.
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