Ravaged by a caterpillar

First detected in Karnataka only in May this year, the fall armyworm, a native of the Americas, has already spread as far as West Bengal and Gujarat, leaving a trail of destruction in its wake. Priyanka Pulla reports on the deficiencies in India’s quarantine regime
It is a hot day in September, and two men are prising open the leaves of maize in a field in Karnataka’s Chikkaballapur district. The crop is two months away from being harvested, but the leaves look diseased. Some have streaks of white on them, while others are peppered with holes. Soon, one of the men, entomologist Arakalagud Nanjundaiah Shylesha, spies the culprit behind these holes — a small greenish-brown worm with dark lines along its length and an inverted ‘Y’ on its head. It looks like any of the thousands of pests that infest fields in India each year, but this one is special. It is the fall armyworm ( Spodoptera frugiperda ), a native of the Americas, which was first seen in Asia five months ago. Since its identification in the State’s Shivamogga district in May, the pest has reached as far as West Bengal and Gujarat. Shylesha shakes half-a-dozen of the caterpillars into his hand. They are of different sizes, which means that they are at different stages, or instars, of the larval life cycle. There are six such instars in the fall armyworm’s life, and between the first and the last, its appetite changes dramatically. Within days, it turns from a light feeder into a voracious eater that can wipe out farms. After pupation, adult moths emerge. As Nanjundaiah carefully transfers the specimens into a plastic bottle, his colleague, Sampath Kumar, remarks, “Not even a single plant is without damage. Oh my god!”
Nanjundiah and Kumar, who are researchers at the the National Bureau of Agricultural Insect Resources (NBAIR), in Bengaluru, are a worried lot. Karnataka is one of the largest maize producers in India, and maize is the third most widely produced cereal in the country. This isn’t the first time a foreign visitor is poised to wreak havoc on Indian farms. In 2008, the papaya mealybug, a central American native, entered the country and destroyed plantations in several States. Then, in 2014, the tomato pinworm, or Tuta absoluta , a South American moth, was spotted in Karnataka. Within a couple of years, it had reached Maharashtra, Gujarat, Delhi and other regions, where it caused widespread damage to tomato crop. Such alien species which migrate to a new geography from their native lands can be a huge risk to both agriculture and wildlife. They could be insects, trees, weeds or viruses. Many of them tend to die out in new environments. Some become naturalised, like a few eucalyptus species have in India. Naturalised aliens maintain their population and do not pose a great risk to biodiversity.
But a small percentage of aliens, like the fall armyworm, turn invasive, which means they spread uncontrollably. The absence of natural predators from their original homes allows them to disrupt ecosystems and cause massive economic losses. In 2016, a paper published in Nature Communications , titled ‘Massive yet grossly underestimated global costs of invasive insects’, calculated that such attacks cost the world around $70 billion a year. Such destruction is why countries take strong measures to prevent the entry of these pests. The first line of defence is a quarantine system, under which imports of grains and plants that can host such insects are inspected at shipping ports, airports and land border crossings. In India, this responsibility lies with the Directorate of Plant Protection, Quarantine & Storage, with its headquarters in Faridabad, Haryana. Unfortunately, many agriculture researchers say, the directorate is failing in its task of policing Indian borders. It is short-staffed and hamstrung by the lack of a strong legislation.
The rise in invasives
Some researchers have argued that India has traditionally been extra vulnerable to invasive species because of its history of political invasions. From the Mughals to the British and the Portuguese, everyone brought their share of noxious weeds, insects and trees. Consider the case of the Lantana species , camara , which was first introduced by the British as an ornamental hedge in the 19th century. Today, it is widespread across India and threatens biodiversity by taking over forest understorey and grabbing resources from other species. Another invasive, congress grass, is thought to have piggybacked via wheat shipments from the U.S. under the 1950s PL-480 Food for Peace program. But the entry of invasives has been rising the world over in the last few decades, and one likely reason is increased trade. Several studies have explored the link between the two. A 2007 analysis of invasive species present in 227 countries found that out of several factors such as a country’s population density and amount of cropland, it was the degree of international trade that best predicted the number of invasives.
In India, data from NBAIR list the entry of several invasive species since 2001: Australia’s eucalyptus gall wasp, Sri Lanka’s sapota seed borer, the South American tomato pinworm, and the papaya mealybug. The papaya mealybug is among the most destructive. First reported in Coimbatore in 2008 by researchers from the U.S.’s Integrated Pest Management Collaborative Research Support Program, the bug spread all over the country quickly. In papayas, it caused a white cottony coating on the fruit and killed papaya trees. But it also survived on over 80 other plants, including mulberry, tapioca, hibiscus and several fruits. “You name the crop, and the mealybug was attacking it,” says Shylesha.. Within two years, the pest spread to over 50 hectares of mulberry in Tamil Nadu, the crop on which silkworms feed. According to one report, the Tamil Nadu silk industry saw cocoon productivity drop by over 60%. At first, farmers turned to chemical insecticides to control the pest. But the insect had a thick, waxy coating on its body, which resisted sprays. Worse, the insecticides were killing the handful of natural enemies the pest had in India, such as ladybird beetles.
Stung by the attack, the Central Silk Board began exploring the idea of classical biological control, which would require importing natural predators of the species from its native country. In this case, the country was Mexico. Eventually, together with the NBAIR, they imported three parasitoids, or insects whose larvae kill the mealybug. After experiments to test whether these parasitoids attacked other beneficial species in India, such as the mulberry silk worm and honeybees, researchers chose one of the three: a wasp called Acerophagus papayae . Today, says Shylesha, the mealybug is mostly under control. But it did cause damage worth Rs. 1,500 crore every year to farmers during the early days. “And this doesn’t include the damage to the environment due to pesticide sprays.” There were things the Directorate of Plant Protection, Quarantine and Storage could have done to prevent the pest from spreading to other States after initial reports, such as imposing restrictions on the movement of plant material from Tamil Nadu. But such a “domestic quarantine” wasn’t imposed, he says.
In August this year, the directorate issued an advisory to the agricultural departments of the States affected by the fall armyworm. It called for extensive surveys to track the pest’s spread. It also named a parasitoid that could be released to kill the eggs of the caterpillar. Further, it also suggested pesticides against the armyworm, such as Lambda cyhalothrin, but cautioned that they shouldn’t be used simultaneously with the parasitoid. But it is already too late for some farmers. One of them is S. Raghavendra, a 35-year-old, whose extended family owns the fields in Chikkaballapur that Shylesha and his team have been surveying. Very few maize stalks in the field are armyworm-free today. When the caterpillar first showed up, Raghavendra visited an insecticide store and the shopkeeper suggested a few pesticides. “But every time I sprayed them, the pest would come back in a week,” Raghavendra said. Now, he fears that he might lose most of his income from his five acre maize farm. I ask him if he knows whether the caterpillar in his fields is a foreign visitor, never seen before in India.
He says he doesn’t, but has a question for me in return. “If this is a new pest, how long will it stay?” As I begin to answer, however, he completes the sentence — “probably forever.”
The customs officer may not suspect anything… Their focus is on items such as gold and narcotic drugs. This is completely different from what a quarantine officer wants to examine.”

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