Race to contain destructive march of armyworm as pest spreads to India
Caterpillar has already migrated from the Americas to Africa, where it devastated billions of dollars worth of maize crops
A crop-chomping caterpillar that has devastated food stocks across Africa has now arrived in southern India, and scientists warn the insect could spread throughout Asia to become a major threat to global food security.
The voracious fall armyworm, which was first spotted on the African continent two years ago and has since cost billions of dollars in crop losses, is best known for gnawing on maize but eats an additional 186 plant species, including sorghum and soybeans.
A pest alert by the Indian Council of Agricultural Research (Icar) reports that Spodoptera frugiperda was identified on 70 per cent of the maize crops examined in Chikkaballapur, Karnataka state, where larvae matched fall armyworm samples from Canada and Costa Rica.
Scientists from the Oxfordshire-based Centre for Agriculture and Bioscience International (Cabi), which developed an action plan to combat the caterpillar’s spread in Africa, now fear that the food security of millions of people across Asia could be at risk if the armyworms are not contained. India produces more than 20 million tonnes of maize a year across the subcontinent, enabling the pest to spread rapidly, Cabi warned.
“A fast response is important as this pest spreads quickly,” said Dr Gopi Ramasamy, Cabi’s country director for India. “It’s likely fall armyworm arrived in India from Africa through human-aided transport, although natural migration is also a possibility since it’s able to fly hundreds of kilometres in one night on prevailing winds.”
Ramasamy said the plan developed and implemented in Africa could be an excellent model to use in India.
“Cabi is ready to assist its national partners in India to manage and control fall armyworm,” he said.
Native to the Americas, fall armyworm arrived in Nigeria in 2016, and quickly spread across 44 countries in Sub-Saharan Africa. While there it showed a growing appetite for other crops, according to the UN Food and Agriculture Organisation, which earmarked US$12 million to combat the pest.
Invasive species cost the global economy US$1.4 trillion every year. Yet infestations generally go undetected or untreated in their initial stages, which prolongs their spread and makes control more difficult, according to Cabi.
“All countries need to be on the alert: the armyworm somehow got from the Americas to Africa and is now in India, so we know it can move long distances,” said Dr Roger Day, Cabi’s programme executive for action on invasive species.
“From looking at environmental suitability, we can work out which conditions seem to favour the fall armyworm and southern China and Southeast Asia are very suitable for it.
“In China, which is in the top two maize producers in the world, maize is grown in the north-east, but it’s colder there, so you might get what you see in the Americas … In the winter the pest is in Florida and Texas, but as it warms up, it can get as far as Canada. So China could still be susceptible to migrant populations.”
The most popular methods of containing the pest include the use of GM crops and pesticides, said Day, but some armyworms have developed resistance to these tactics and are continuing to blight crops.
Cabi is now investigating natural approaches, including breeding predators such as wasps, to be released into fields when necessary, as well as developing a “germ warfare” that isolates diseases to which the caterpillar is prone.
“There are lots of ways to kill the fall armyworm, but getting them deployed cost-effectively is the issue,” said Day.