In Arid Trans-Himalayas, a Rise in Pest Attacks Indicates Changing Climate Conditions

Pests like aphids and scale insects, which until now have remained unseen in the region, have wrecked havoc on crops and lead to huge economic losses.

Sometime in early August, a team at the Central Arid Zone Research Institute in Leh was studying leaves of poplars, a fast-growing tree that is abundant in Ladakh and – along with timber – provides a spectacular cover of green in the arid trans-Himalayan region. Only this year, the leaves were wilted and left brown in patches after an insect used them as a host to breed. The scientists at the institute were trying to identify the insect.

In the nearby Kargil region, another fast-growing tree, willow, has been suffering from the menace of giant willow aphid, a sap-sucking pest that colonises the host tree and grows exponentially in a couple of weeks. Ngawang Dorjay, a researcher who studied entomology at Sher-e-Kashmir University of Agricultural Sciences and Technology (SKUAST) is concerned about their growing numbers. “It’s only since last four-five years that aphids have become a major nuisance,” he said. He has observed growing aphid attacks on other plants like green, leafy vegetables and on apricots, a prime cash crop in the region.

Aphids have been a common pest species in the region. However, last year it attacked apricot trees with such unseen aggression that it led to an economic loss of Rs 545 lakh in the Khalsi and Turtuk belt, according to the Defence Institute of High Altitude Research (DIHAR).

In fact, 2016 was one of the worst years for apricot cultivators in the region because along with aphids, another insect – either brown or yellowtail moth – wreaked havoc on apricot trees. It was commonly referred to as the defoliating caterpillar. After surviving one of the world’s harshest winters, the insect (at the caterpillar stage in its life cycle) crawled out to voraciously feed on new spring-time leaves causing absolute defoliation of trees. In a presentation, Tsering Stopdan, a senior scientist at DIHAR, observed: “From a distance, it appears
 that the entire apricot trees in the Dah-Hanu villages having been burnt down.” The caterpillar was so ruthless that the affected villages in Dah-Hanu belt of Ladakh incurred economic losses of Rs 223.5 lakhs (in addition to losses caused by the aphids). The hair of the caterpillar caused strong skin reactions and respiratory problems, leading to a temporary migration of people from the affected areas towards Leh for medical assistance.

“Insects are pests, they need a certain climatic condition to grow their population. Ladakh never provided that exact combination to pests like aphids or scale insects, until now,” explained Dorjay.

Dorjay is from Zanskar, a region that has been hosting another unwelcome visitor, the extremely notorious Locusta migratoria that chomps on to anything it encounters on its way. While locusts are not a new invasive species of pest in the region, the plague they caused in 2006 was shocking for Dorjay. They invaded the Zanskar in swarms, leaving behind ruined agriculture and pasturelands in its wake. And returned with same fierceness in 2011 and 2015.

For a decade or so, the wheat cultivators are complaining of a fungal disease, the yellow rust. Sharab Angmo, a farmer in Basgo village of Ladakh, plucks out the infected crop plants and shows the shrivelled and stunted grain on her palm. “The rust eats off out most of our yield,” she said, dusting off a powdery coating of reddish-brown rust from the stem of the wheat plant.

Probable reasons

There have been occurrences of insect infestation in Ladakh in the past. Maggots in onions, or cutworm in vegetables, or the old and infamous native of the region, the codling moth because of which Ladakh suffers a domestic quarantine – imposed in 1981 under the Jammu and Kashmir Plant and Disease Act – under which export of fresh apples and apricots to other Indian states is banned. But there is no denying that subtle changes in the region are underway.

“The yellow rust, the defoliating caterpillar and the locust indicate changing climate in the region,” asserts Vikas Gupta, a scientist at SKUAST. “Yellow rust in wheat is ubiquitous in states like Punjab but the earlier climate of Ladakh did not support this disease,” he says. Gupta was also a member of a committee formed by Ladakh Autonomous Hill Development Council to fight the outbreak of defoliating caterpillar. Stopdan, who chaired this committee, expressed his surprise that the defoliating caterpillar was able to survive the trans-Himalayan winter. At the time of breakout, the insect created a crises situation because its outbreak is not recorded elsewhere in the country. The situation was finally controlled with pesticides.

Professor D.P. Abrol from the division of entomology of SKUAST, Jammu explains that insect behaviour is a reliable marker for climate variation, and studying these frequent episodes of insect infestations and break-out in Ladakh will deepen our understanding of climate change in trans-Himalayas. Last year, three scientists analysed the meteorological data of Leh from 1901 to 2012 and concluded that mid-1990s onwards, the temperature is showing a rapidly increasing trend in the region. Abrol refers to this study and carefully reads out a note from his lecture: “Increased temperature could increase insect populations by potentially affecting the insect survival, development, geographic range, population size and insect physiology and development directly or indirectly through the physiology or existence of host.”

Aphid infestation. Credit: Luke Jones/Flickr (CC BY 2.0)

Aphid infestation. Credit: Luke Jones/Flickr (CC BY 2.0)

What is the way forward?

A popular method to avoid yellow rust is growing genetically-modified varieties that are resistant to these pathotypes. But the local farmers have eventually come to reject them. “The fodder it gives is not liked by our animals. It is hard to chew,” Angmo said. The other alternative is using a fungicide, propiconazole, which is now gaining some acceptance.

Pesticides, however, are an unpopular mode of treatment in Ladakh. The local Buddhist beliefs condemn the killing of any life-form, be it an insect, making the use of pesticides ‘sinful’. The tradition also has the support of Ladakh Autonomous Hill Development Council, but aggressive breakouts like that of apricot defoliator caused such menace that authorities had no choice but to cull the outbreak with pesticides. With frequent and aggressive outbreaks of insects, the people have reluctantly and slowly started accepting the pesticides. Pesticides sprayers have been made available at a subsidy up to 80%, one of the cheapest in India. But Abrol cautions against the excessive use of pesticide, which can alter pest behaviour for the worse. “Pesticides should always be used in controlled measure after scientific study,” he said. 

Agriculture scientists of major organisations had joined forces to fight the breakout and have now initiated many drives that educate farmers on maintaining sanitation and cleanliness in orchards, a practice not usually followed in the region. The outbreak of defoliating caterpillar has set in motion a management system that includes a healthy mix of physical, chemical and biological pest management techniques. In the last week of September, the minister for horticulture, Syed Basharat Bukhari called for efficient integrated pest management strategies in Ladakh region to tackle agriculture pest and insects damaging crops.

Another development in the last decade is the increased use of many genetically modified or hybrid plants in the area. Many hybrid varieties are modified to be resistant to diseases and insects. “Hybrid varieties have also been used here because of which the dormant behaviour of the insects can become aggressive. High yielding varieties need a lot of nutrition. So urea is added to the soil and soil nature changes. It is better to grow indigenous varieties,” Gupta says.

In summers, each house in Leh has a spectacular garden with exotic flowers, and a flourishing kitchen garden. Rigzen Norboo is in his mid 50s and maintains a small farm where he grows fresh vegetables. “Now I grow more vegetables and buy wheat from the market. Vegetables have started to grow well, even brinjal and capsicum come alright outside the greenhouse shed,” he says. He feels the rains have changed from when he was a boy. “It rains a lot more these days,” he says. “It gives a good yield.”

There is no argument that the green cover over Ladakh has considerably increased in last two-three decades. The number of fruit trees has also grown in the Leh city. “People have now started growing Red Delicious, a variety of apple in Kashmir. Earlier you wouldn’t find it in Ladakh,” says Stopdan. There is some change underway in this trans-Himalayan region. There are subtle or strong signs of this change everywhere. “Our crops are changing, snow and rain patterns are changing, insect attacks have increased and floods have become a norm,” says Tsewang Stanzin Yokma, who lives next to the Gya village that was flooded because of glacial lake outburst in August 2014. “There is too much happening together in our times, maybe it is a sign of some big change,” he said.

Preksha Sharma is currently based in Mumbai and is the assistant editor of The Indian Quarterly. The story is being published as part of IHCAP-CMS Media Fellowship Program.