The recent surge in whitefly attacks on cotton crops across various states, such as Punjab and Rajasthan, has drawn attention to this agricultural issue. Whiteflies are a substantial threat to these crops, causing significant damage and lowering yield. The spread of these pests throughout the country and their resistance to traditional insecticides has led to increased concerns among farmers and authorities alike.
The Impact and Spread of Whiteflies
Whiteflies are destructive pests for cotton crops, feeding on the sap of leaves and spreading diseases such as Cotton Leaf Curl Virus which greatly affects the photosynthesis process, thereby weakening the overall health of the plant. They discharge fluid onto the leaves where a black fungus grows, which in turn, limits photosynthesis.
Two invasive species of whiteflies, the Aleurodicus dispersus and Aleurodicus rugioperculatus, originally reported in different regions of India, have now spread throughout the country, affecting over 320 and 40 plant species respectively. Most whitefly species originate from the Caribbean islands or Central America.
Reasons for the Whitefly Invasion
The widespread invasion of these pests is attributed to their polyphagous nature that enables them to feed on a variety of food sources, coupled with their prolific breeding habits. An increased import of plants, globalization, and human movement have further contributed to the spread of different whitefly varieties and their growth into invasive species.
Damage Caused by Whiteflies
Whiteflies significantly reduce crop production and cause extensive damage. In India alone, about 1.35 lakh hectares of coconut and oil palm are affected by the rugose spiralling whitefly. Other invasive whiteflies have also expanded their reach to valuable plant species, including coconut, mango, guava, cashew, and various ornamental and medicinal plants.
Regrettably, whiteflies have proven to be resistant to available synthetic insecticides, making them hard to control.
Efforts to Control Whiteflies
The present methods to control whiteflies involve the use of natural insect predators, parasitoids (natural enemies of pests that provide biological pest control in greenhouses and crop fields), and entomopathogenic fungi which are capable of killing insects.
Other Pests Threatening Crops
Whiteflies aren’t the only pests threatening crops. The Fall Armyworm (FAW), a dangerous transboundary insect, has a high potential for rapid spread due to its natural distribution capacity and opportunities presented by international trade. In 2020, an attack on standing crops in Assam’s northeastern Dhemaji district was reported.
Locusts, large tropical grasshoppers with strong powers of flight, are another significant threat. Their ability to change their behavior, form swarms, and migrate large distances makes them particularly destructive as they eat their own weight in fresh vegetation every day.
The Pink Bollworm (PBW), another pest native to Asia but now invasive worldwide, is known for the significant damage it causes to cotton farming.