Whitefly is a major pest. White fly has become an economically significant pest in recent years, causing substantial output loss in agriculture, horticulture, and decorative crops with the introduction of Bt cotton. Because of its rapid rate of population build-up, mobility, polyphagy nature, and capacity to spread viral vectors such as Cotton Leaf Curl Virus (CLCV) and propensity to generate black sooty mold on the leaf, it is regarded as a most critical pest from an economic standpoint.
Cotton is a major commercial crop in India, with 9 million hectares produced under various agroecological conditions. It supplies raw materials to the cotton textile industry as well as direct employment for 6 million farmers. Cotton is farmed in ten states in India, which are classified into three zones (north, central, and south). It is also cultivated in tiny areas of other states. In India, 24 insects and mites have been identified as pests that cause considerable output loss. Sap-feeding insects, bollworms, leaf-feeding insects, and mites are among the pests.
Whitefly management in Cotton
The life cycle of a Whitefly
Bemisia tabaci, Known as Whitefly, has four life stages: egg, nymph, pupa, and adult. The female Whitefly deposits her eggs on the underside of leaves, and the eggs develop into nymphs. Before pupating, the nymphs feed on plant sap and go through multiple molts. After about a week, adult whiteflies emerge from the pupal stage. Under ideal conditions, the life cycle from egg to adult can be completed in as little as two weeks, allowing for fast population expansion.
Favorable conditions favoring an increased population of Whitefly in the field
High humidity and moderate temperature, delayed crop sowing, stress caused by lack of moisture, poor quality water, water logging, saline soil, nutrient deficiency, poor weed management, and even higher nitrogen fertilizer application are all conditions that favor the increased whitefly population in fields.
Identification of the Whitefly
- Whiteflies have different stages of development: eggs, nymphs, pupae, and adults.
- Eggs are yellowish-white, laid on the undersides of leaves, and have a sub-elliptical shape.
- Nymphs are yellowish-brown, scale-like, and found in large numbers on the undersides of leaves.
- Pupae are similar in shape to nymphs with brownish opercula.
- Adults are tiny and white, with a yellow body lightly dusted with a white waxy powder. Females are 1.1-1.2mm long with longer antennae than males, while males are slightly smaller with extended, narrow, and pointed parameres.
Symptoms of damage by Whitefly
- Chlorotic spots on leaves merge to form irregular yellowing of leaf tissue, extending from veins to the edges of the leaves.
- Premature defoliation due to severe infestation.
- Development of sooty mold due to the production of honeydew by whiteflies.
- Shedding of buds and bolls, leading to poor boll opening.
- Transmission of leaf curl virus diseases, causing further damage to cotton plants. Overall, whitefly infestation can significantly reduce crop yields and quality.