Locust attack and the way forward

Locust attack and the way forward

Locust attack and the way forward

Author: Rumi Saikia
Read time: 5 mins 11 secs

Swarms of desert locusts coming from across the Indo-Pak border have destroyed over 50,000 Hectares of cropland in India’s northwest and central regions. In Rajasthan’s Bikaner alone, about 700 hectares of cotton plantation have been devastated whose estimate in monetary terms is about ₹100 million. India hasn’t had a locust attack of this magnitude since 1962. Occurrence of locusts is considered a regular feature, but this year’s occurrence is a once-in-three-decade situation and is especially badly timed when the country is already grappling with a health crisis.

What are locusts?

Desert Locusts (Schistocerca gregaria) are large, mainly tropical, flying grasshoppers that migrates in large swarms and cause huge damage to vegetation. They are considered the most destructive migratory pests and are called farmer’s enemy for a reason. Locusts feed on nearly all green vegetation – leaves, flowers, bark, seeds, stems and fruits. Although, locusts are harmless if solitary, they undergo behavioural changes when their population raises rapidly. When the swarms are large enough, they enter the gregarious phase and that’s when they become destructive and devour every bit of greenery on their way. A single swarm can contain up to 80 million locusts and can spread over an area of a square kilometre. African countries Ethiopia and Somalia are experiencing one of the worst locust attacks in 25 years as I write.

What caused their outbreak?

In 2018, cyclonic storms Mekunu and Luban that struck Oman and Yemen, turned desert tracks into huge lakes. These lakes facilitated locust breeding that continued through 2019. The swarms travelled through East Africa reaching peak population in November and then built up in Iran and Pakistan in early 2020. Heavy rains in east Africa further enabled their breeding.

Why is India affected?

According to a climate scientist at the University of Maryland, US, the winds that enter India to the north of the Western Ghats split into North-westerlies. One branch continues towards the central and north-eastern India and the other towards the southeast. The swarms of locust are assumed to have taken the southern branch of split. This branch of wind has taken the locust more toward Madhya Pradesh that lies south east of Rajasthan. There is a large scale contrast in land-ocean heating which leads to surface pressure contours. These contours tend to align from southeast to northwest of India, so the wind that enter India north of the Western Ghats follow these routes.

Other than the general wind patterns, the localised winds are also crucial in understanding where the locusts will move next.

A senior scientist at Indian Institute of Tropical Meteorology has noted that warm waters in the western Indian Ocean in late 2019 triggered heavy amounts of rain in East Africa and the Arabian Peninsula and turned parts of Rub’ al-Khali desert watery. These warm waters were caused by a phenomenon called Indian Ocean Dipole, where warmer waters move to the west and cooler waters move to the east. Rising temperatures due to global warming amplified the Dipole and made the Indian Ocean particularly warm. After heavy rain triggered the growth of vegetation in drylands like the Rub’ al-Khali and both coasts of the Red Sea, desert locust grew and bred, which ultimately migrated to India and found greener pastures.

What will happen if locusts are left uncontrolled?

As of now, there has been no impact on the Rabi crops, as they have already been harvested. Rabi crops or winter crops are crops such as wheat, pulses, and oilseeds. However, if infestation is not controlled, it will lead to an outbreak prior to arrival of monsoon rainfall in June-July when locusts will mature and breed. An adult female locust lays 80-90 eggs thrice in her three-month life cycle. If left uncontrolled, a swarm can grow exponentially to 40-80 million locusts per square kilometre. The locusts will start laying eggs after the monsoon starts and continue breeding for two more months, with newer generations rising during the growth phase of the kharif crop.

What does it take for NPM practicing farmers to resist locust attacks?

Most solutions to control locust breeding and locust attacks involve spraying of chemical pesticides. In fact, the India govt., has ensure spraying of 53,000 litres of Malathion in Rajasthan which is the worst affected state with 21 district under attack. Malathion, in low amounts is not considered toxic, however, if consumed in large amounts has strong biological effects. Overexposure to the insecticide may produce a variety of symptoms in animals and humans including: nausea, dizziness, sweating, salivation, runny nose and watery eyes. Studies say that Malathion, after it’s sprayed, finds its way into the rivers and other water bodies through rain. We can imagine the health hazards after water from these natural water bodies reach the human and animal body.

Although no fool-proof remedy has been conceived, there are a few bio-remedies that have been found effective by farmers. Burning of neem leaves has been proven highly efficient in driving these pests away. Spraying of garlic oil and neem oil are also a few locust resistant solutions. A linseed/bicarbonate solution dissolving 1 g NaHCO3 powder in 10 ml distilled water and then adding a 50ml of linseed oil is a highly effective insecticidal agent to impair the motion of locusts.

The results showed that Due to the hardening process of the linseed/bicarbonate emulsion, locust mobility was strongly restricted after 24 h. Results of spraying formulation containing linseed and other essential oil like wintergreen, orange peel, garlic, caraway etc. showed that essential oils had a strong effect on the mortality rates of the gregarious locust species; firstly, affecting mobility and secondly and most likely affecting ventilation. The application of these bio-pesticides affects only the targeted locusts and does not harm crops and other species like worms and beetles.

Let us hope that this calamity is contained with minimal harm to the ecosystem and the food we consume.