Managing mealy bug menace in cotton

The occurrence of solenopsis mealy bug, Phenacoccus solenopsis on cotton was reported from Gujarat during 2004-2007. Since then, the insect has become a serious pest in cotton growing states in India. The yield loss due to this pest was estimated to be up to 50 per cent.

Even the Bt cotton fields were also reported to be heavily infested with this species of mealy bug. This mealy bug is favoured by dry weather and many records refer to heavy attacks following periods of prolonged drought.

Appearance

The mealy bug is cottony in appearance, soft bodied, oval shaped covered with white mealy wax. It feeds on young shoots and leaves. Affected plants appear sick and black, resulting in reduced fruiting capacity.

Heavy infestations often kill the shoots completely. Clustering of mealy bugs is usually seen under surface of leaves as a thick mat with waxy secretion. Excess excretion of honey dews promotes the growth of sooty mould, interfering with photosynthesis.

The mealy bug lays around 500 eggs from which the first instar called the crawlers emerge. They all move to suitable places in the plant, get fixed and start sucking the plant sap causing damage. Nymphal period lasts for about 15 days and the adults survive up to 35 days.

Management methods

— Maintain field sanitation. Remove alternate weed hosts.

— Collect and destroy the infested twigs and branches or even uproot the severely infested plants.

— Monitor the incidence regularly and look for crawler emergence.

— Dust with 2 per cent methyl parathion. Spray profenofos 50EC , chlorpyrifos 20EC , quinalphos 25EC or dimethoate 30EC at 2ml/lit.

— Apply Neem oil 2 per cent, Neem Seed Kernel Extract 5 per cent or Fish oil rosin soap at 25g/litre of water. In nature, many lady bird beetles, green lacewing flies, parasitoids and entomopathogenic fungi effectively control this mealy bug.

(Dr. J. Jayaraj, Professor and Dr. M. Kalyamasundaram, Professor and Head, Entomology dept, Agricultural College and Research Institute, Madurai 625 104, Phone: 0452-2422956 Extn.214, Email: agentomac@tnau.ac.in)