Mealy bug — a new threat to cotton cultivation
Cotton crops in Punjab, Rajasthan, Maharashtra, Andhra Pradesh, Gujarat and Tamil Nadu are being seriously infested with mealy bugs during the last 2-3 cropping seasons.
In Tamil Nadu the pest has been observed in Salem, Coimbatore, Perambalur, Erode, and Virudhunagar districts.
Mealy bugs are small, soft bodied sucking insects which suck the sap from the stem, twigs, leaves, flower buds and young bolls.
Sooty mould
A sugary liquid secreted by these insects falls on the leaves and serves as a medium for the growth of sooty mould, a fungus that reduces photosynthetic ability of the plant.
Adult female lays 400-600 eggs in a thin bag called ovisac and within 3-9 days young mealy bugs called crawlers emerge from the ovisac.
The crawlers actively spread through various means and settle down in 25-30 days.
The pest causes premature leaf drop, dieback and death of plants if unchecked.
Serious attack of the pest results in bunchy growth, plants remain stunted and produce fewer bolls. Heavy clustering of mealy bugs can be seen on lower surface of leaves giving the appearance of a thick mat with waxy secretion.
The honeydew excreted by the mealy bugs attracts ants which help in spreading of the pest and provide protection from predators and parasites.
Management
—Field borders should be free from weeds.
—Crop residues with infestation should be removed and burnt.
—Plough the infested fields to expose the immature stages in the soil to the biotic and abiotic factors.
—Discourage growing alternate host plants such as hibiscus, okra, custard apple, guava in nearby cotton fields.
— Encourage cowpea as border crop on bunds and irrigation channels to enhance the multiplication of predatory insects.
— Ant fences should be treated with chlorpyriphos 20 EC at 2.5 ml/lit through drenching (or) by application of malathion dust 5 per cent at 25 Kg/ha .
B. Dhara Jothi &
N. Gopalakrishnan
Central Institute for Cotton Research
Regional Station
Coimbatore, Tamil Nadu
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