Whiteflies: Threat to Agriculture

• 25 May 2021

Why in News

According to a recent study, exotic invasive whiteflies in India are causing direct and indirect yield losses in agriculture, horticulture and forestry crop plants.

• Whiteflies are tiny, sap-sucking insects that may become abundant in vegetable and ornamental plantings, especially during warm weather. They excrete sticky honeydew and cause yellowing or death of leaves.

Key Points

• Spread of Whiteflies:
  
  • The first reported invasive spiralling whitefly (Aleurodicus dispersus) is now distributed throughout India except Jammu & Kashmir.
  • Similarly, the rugose spiralling whitefly (Aleurodicus rugioperculatus) which was reported in Pollachi, Tamil Nadu in 2016 has now spread throughout the country including the islands of Andaman Nicobar and Lakshadweep.
  • Aleurodicus dispersus and Aleurodicus rugioperculatus have been reported on over 320 and 40 plant species, respectively.
  • Most of the whitefly species are native to the Caribbean islands or Central America.
• Reasons for Spread:
  
  • The host range of all of the invasive whiteflies has been increasing due to their polyphagous nature (ability to feed on various kinds of food) and prolific breeding.
  • The increasing import of plants and increasing globalization and movement of people has aided the spread of different varieties and their subsequent growth into invasive species.
• Concerns:
  
  • Damage to Crops:
    
    • Whiteflies reduce the production yield and also damage crops. Approximately 1.35 lakh hectares of coconut and oil palm in India are affected by the rugose spiralling whitefly.
    • Other invasive whiteflies were also found to expand their host range on valuable plant species, especially coconut, banana, mango, sapota, guava, cashew, oil palm, and ornamental plants such as bottle palm, false bird of paradise, butterfly palm and important medicinal plants.
  • Ineffectiveness of Insecticides:
    
    • Whiteflies have been difficult to control by using available synthetic insecticides.
• Controlling Whiteflies:
  
  • Biological Control Methods:
    
    • They are currently being controlled by naturally occurring insect predators, parasitoids (natural enemies of pests, provide biological control of pests in greenhouses and crop fields) and entomopathogenic fungi (fungi that can kill insects).
    • Entomopathogenic fungi specific to whiteflies are isolated, purified, grown in the lab or mass-produced and applied into the whitefly infested field in combination with the release of lab-reared potential predators and parasitoids.
    • They are not just environmentally friendly but also economically feasible.

Other Pests/Insects Attacking Crops

• Fall Armyworm (FAW) Attack:
  
  • It is a dangerous transboundary insect with a high potential to spread rapidly due to its natural distribution capacity and opportunities presented by international trade.
  • In 2020, the Directorate of Agriculture reported an armyworm attack on the standing crops in the northeastern Dhemaji district of Assam and the Food and Agriculture Organisation (FAO) has launched a Global Action for FAW Control as a response to the international threat posed by the armyworms.
• Locust Invasion:
  
  • A locust (Migratory insect also known as tiddi) is a large, mainly tropical grasshopper with strong powers of flight. They differ from ordinary grasshoppers in their ability to change behaviour (gregarize) and form swarms that can migrate over large distances.
  • Locust adults can eat their own weight every day, i.e. about two grams of fresh vegetation per day. A very small swarm eats as much in one day as about 35,000 people, posing a devastating threat to crops and food security.
• Pink Bollworm (PBW):
  
  • It (Pectinophora gossypiella), is an insect known for being a pest in cotton farming.
  • The pink bollworm is native to Asia, but has become an invasive species in most of the world’s cotton-growing regions.

Way Forward

• Continuous monitoring of the occurrence of invasive species, their host plants and geographical expansion is needed, and if required, import of potential natural enemies for bio-control programmes can also be carried out.

Source:TH