Whiteflies are small, sap-sucking insects commonly found on the underside of leaves. They belong to the family Aleyrodidae and are a major pest of many crops, including Green Gram. Whiteflies can cause significant damage to plants by feeding on the sap, leading to stunted growth, reduced yield, and transmission of viral diseases.
There are several species of whiteflies, but the most common ones found in Green Gram are the Bemisia tabaci and Trialeurodes vaporariorum. Both species are polyphagous, meaning they can feed on various plants, including weeds and ornamentals. Managing whiteflies in Green Gram requires a combination of cultural, biological, and chemical control methods.
Cultural practices such as crop rotation, planting resistant varieties, and proper sanitation can help reduce whitefly populations. Biological control agents like parasitic wasps and predators like lady beetles and lacewings can also control whiteflies. Chemical control should be used as the last option. To avoid damaging non-target insects and the environment, apply insecticides at the recommended rates and schedule.
Whitefly Management in Green Gram
Identification of Whitefly
Whiteflies are small insects; their body and each pair of wings are covered with a white to yellowish powder, waxy secretion. They measure between 0.8 and 1 mm and have a distinct appearance. Whitefly eggs are deposited on the underside of the leaves, where they hatch into yellow to white, flat, oval, and pale green-colored nymphs. Adult whiteflies cannot survive for a few days without feeding on a host plant. Commonly found on the underside of the leaves, they will form a cloud if disturbed.
The Life Cycle of Whitefly
The life cycle of a whitefly can be divided into four stages: egg, nymph, pupa, and adult. The eggs of whiteflies are tiny, measuring only 0.2 mm in length. They are laid on the underside of leaves, where they hatch into first instar nymphs that are only 0.3 mm in size. The nymphs go through two to three instars, increasing in size to 0.4-0.6 mm.
They then develop into fourth instar or red eye pupae that are 0.6-0.8 mm long. Finally, the adults emerge, minute insects with yellow-colored bodies covered in white waxy bloom. The entire life cycle takes around 18 to 28 days in warm weather.
Causes/Conditions Favorable for Whitefly Spread in the Field
Whiteflies can multiply and spread quickly when the temperature is high, the humidity is low, and the air is dry. Overcrowding of plants, lack of proper sanitation practices, and the presence of weeds can also contribute to the rapid spread of whiteflies in the field
Damage Symptoms of Whitefly
Whiteflies cause major damage to plants by feeding on their sap. Both the nymphs and adults of whiteflies can be found in large numbers on plants, and their feeding can result in yellowing and mottling of leaves, stunted growth, and premature defoliation. Severe infestations can lead to the shedding of flowers and pods and the development of sooty mold or honeydew on the leaves. Whiteflies are known to spread plant viruses, like the yellow mosaic virus, and the damage they do when they eat.Â
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Yield Loss Due to Whitefly on Green Gram
Infestations of whiteflies can cause yield losses of at least 40 percent in green gram crops. The annual yield loss caused by whiteflies and other insect pests can have a significant economic impact on growers, highlighting the need for efficient management strategies.
Whitefly Management in Green Gram by Cultural Method
- Crop rotation: Growing green gram after crops that are not a host of whiteflies like maize, sorghum, or millet.
- Intercropping: Planting non-host crops like cowpea or maize between green gram rows.
- Early planting: Planting green gram early in the season when the population of whiteflies is still low.
- Use of resistant varieties: Planting green gram varieties is less susceptible to whiteflies.
- Sanitation: Removing and destroying weed hosts of whiteflies and removing infected plant debris after harvest.
- Traps: Using yellow sticky traps to capture adult whiteflies and reduce their population.
Whitefly Management in Green Gram by Biological Method
- Pathogenic fungi like Beauveria bassiana, Isaria fumosorosea, Verticillium lecanii, or Paecilomyces fumosoroseus infect and kill whiteflies.
- Parasitic wasps encourage the presence of parasitic wasps like Encarsia formosa and Eretmocerus eremicus, which lay their eggs in whitefly nymphs, preventing them from developing into adults.
- Predatory insects like ladybugs and lacewings feed on adult whiteflies and their eggs.
- Biological control agents like Bacillus thuringiensis infect whiteflies with a fatal disease.
Whitefly Management in Green Gram by Chemical Method
- Chemical control: Using insecticides like malathion, phosalone, or dimethoate to control whiteflies.
- Recommended dosage: Applying 1.0 L of malathion 50 EC or 750 ml of phosalone 50 EC or dimethoate 30 EC per hectare in 700-1000 L of water.
- Other options: Using products based on or combinations of bifenthrin, buprofezin, fenoxycarb, deltamethrin, azadirachtin, lambda-cyhalothrin, cypermethrin, pyrethroids, pymetrozine or spiromesifen to control whiteflies.
- Caution: Chemical control should be a last resort and applied only when the infestation is severe and other control measures have failed.
Whitefly Management in Green gram by Organic/Natural Method
- Natural insecticides: Use organic or natural insecticides like sugar-apple oil, pyrethrins, insecticidal soaps, Neem seed kernel extract (NSKE 5%), or Neem oil (5ml/L water) to control whiteflies.
- Specific solutions: The choice of biological solution depends on the whitefly species and the crop being grown.
- Sugar-apple oil: Annona squamosa oil effectively controls whiteflies by disrupting their feeding and egg-laying behavior.
- Pyrethrins: Derived from chrysanthemum flowers, pyrethrins are natural insecticides that kill whiteflies by disrupting their nervous system.
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Preventive Measures for Control of Whitefly
Prevention is key in controlling whiteflies. Companion crops, border crops, proper timing, plant spacing, and monitoring are effective preventive measures. Balanced fertilization, selective pesticides, controlling weeds and alternate hosts, removing crop residues, and intercropping can also help. Avoiding broad-spectrum insecticides that harm beneficial insects is essential.
Conclusion
Whiteflies are major pests of green gram, causing significant yield losses. Identification of symptoms and early detection is crucial for effective management. Various control measures include chemical, biological, natural, and organic methods. Prevention is key; farmers can use companion crops, border crops, proper timing, plant spacing, and monitoring. Selective pesticides, controlling weeds, crop residues, and intercropping can help reduce whitefly populations.
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