From devastation to recovery: How a parasitic wasp saved South India’s tapioca crops
Two years after scientists from the National Bureau of Agricultural Insect Resources (NBAIR) of the Indian Council of Agricultural Research (ICAR) released a tiny parasitic wasp into the tapioca fields of South India, the crop, once nearly devastated by an invasive pest, is now thriving again. Farmers in Tamil Nadu, Kerala and Puducherry reported tapioca harvests returning to pre-pandemic levels. This marks a rare success in controlling a major agricultural pest without chemicals.
Cassava, better known as tapioca, is grown in around 1.73 lakh hectares in India, with Tamil Nadu and Kerala together contributing more than 90% of the total production. According to NBAIR officials, before the pandemic, yields averaged 35 tonnes per hectare, well above the global average of 10.76 tonnes, and India was exporting value-added tapioca products worth around ₹200 million annually.
But the mealybug’s arrival in Thrissur, Kerala, in April 2020 changed the landscape. By 2021, around 1.43 lakh hectares were invaded and some parts of Tamil Nadu saw yields drop to 5-12 tonnes per hectare. It feeds on harmful plant sap, causing leaves to curl, slow growth, and poor tuber formation. Due to the lack of effective native predators, the infestation increased rapidly and posed a serious economic threat to farmers.
Chemical sprays were considered, but the continued use of pesticides was costly, harmful to the environment, and unsustainable for small farmers. ICAR-NBAIR scientists instead turned to classical biological control, a strategy that introduces a natural enemy from the pest’s native range to restore ecological balance.
“Every species in nature has natural enemies that keep its population in check. Scientists have identified a small parasitic wasp, Anagyrus lopezi, which specifically targets the cassava mealybug. The wasp lays its eggs inside the pest and the developing larvae consume it from within, naturally reducing the number of mealybugs without harming other crops,” said SN Sushil, Director, ICAR-NBAIR.
After identifying the parasitoid Anagyrus lopezi as a suitable natural enemy, the institute imported a shipment from the International Institute of Tropical Agriculture (IITA) in Benin, West Africa, as part of its mission to introduce live biological control agents for pest management. Strict quarantine studies at NBAIR facilities confirmed the host specificity and biosecurity of the wasp, enabling it to target only cassava mealybug without affecting other crops or beneficial insects.
The first field release of A. lopezi was conducted in March 2022 at Yethapur in Salem district with approximately 300 farmers. This was followed by large-scale broadcasts covering more than 500 farmers’ fields in Tamil Nadu, Kerala and Puducherry. To support adoption, ICAR-NBAIR established three satellite mass production centers, distributed more than 200,000 parasitoids, and conducted 25 awareness programs and numerous training sessions. Parasitoids spread naturally up to 30-40 km beyond their point of release, gradually bringing the mealybug population under control.
By 2023-24, the program has achieved remarkable results. Yields in the worst-affected areas, including Salem, Namakkal, Dharmapuri, increased to 35 tonnes per hectare and farmers’ income and livelihoods were restored. Mealybug is now under natural control in 1.43 lakh hectares of area that was previously infested, eliminating the need for chemical sprays.
The team behind the initiative includes Sampathkumar M., M. Mohan, AN Shylesha, Sunil Joshi, Ankita Gupta and Mr. Sushil, who are still monitoring the spread of the parasitoid.
It was published – 22 October 2025 16:44 IST
