WHITEFLIES IN COTTON

Telugu name: Thella doma

Scientific name: Bemisia tabaci

Identification of the Pest:

Destructive stage: Nymphs and adults.
Eggs: Yellowish white laid singly on the under surface of leaves. Egg period: 3-5.
Nymph: Greenish yellow, oval in outline
Pupa: Oval in shape, present on the under surface of the leaves
Adult: Minute insects with yellow body covered with a white waxy bloom.

Life cycle:

• Eggs hatch in about 3-5 days.
• Nymphs grow through three stages.
• Become pupae in about 9-14 days during summer and 17-81 days during winter.
• Pupal period is of 2-8 days.
• Total life cycle is completed in 14-122 days.

Symptoms:

• Chlorotic spots on the leaves which latter coalesce forming irregular yellowing of leaf tissue which extends from veins to the outer edges of the leaves.
• Severe infestation results in premature defoliation.
• Development of sooty mould.
• Shedding of buds and bolls and poor boll opening.
• It also transmits the leaf curl virus diseases of cotton.

Favourable Conditions:

• Whiteflies thrive when temperatures are high (above 30°C). Hot and dry conditions are ideal for their growth.
• When there is less rain or no rainfall, whiteflies multiply quickly. Rain can wash away whiteflies and their eggs.
• High Humidity i.e. above 60% supports their survival and reproduction.
• Overcrowded cotton plants create a humid and shaded environment, which is perfect for whiteflies.
• Continuous use of certain pesticides can make whiteflies resistant, leading to uncontrolled infestations.
• Whiteflies also feed on other plants like okra, brinjal, and weeds. If these are near cotton fields, they can serve as breeding grounds.

ETL: 5-10 Whiteflies/leaf.

Management:

Cultural practices:

• Avoid the alternate, cultivated host crops of the white fly in the vicinity of cotton crop.
• Growing cotton only once a year either in winter or summer season in any cotton tract.
• Adopting crop rotation with non-preferred hosts such as sorghum, ragi, maize etc., for the white fly to check the build up of the pest.
• Removal and destruction of alternate weed hosts like Abutilon indicum (Thuthi), Chrozophorerottlari(Purapirakkai), Solanumnigrum(Manathakali/Milaguthakali, Chukkittikeerai)
and Hibiscus ficulensusfrom the fields and neighbouring areas and maintaining field sanitation
• Timely sowing with recommended spacing, preferably wider spacing and judicious application of recommended dose of fertilizers, particularly nitrogenous and irrigation management is essential to arrest the excessive
vegetative growth and pest build up.
• Field sanitation may be given proper attention. 
• Monitoring the activities of the adult white flies by setting up yellow pan traps and sticky traps at 1 feet height above the plant canopy and also in situ counts.Collection and removal of whitefly infested leaves from the plants and those which were shed due to the attack of the pest and destroying them.