As the global population increases, humankind is placing increased demands on the planet for land, food and water. Agricultural practices have intensified, but, despite this, two billion of the 9 billion people on earth still experienced food insecurity in 2019.
While food insecurity stems mainly from a mix of political, economic and agricultural causes, climate change also poses a number of threats. For example, increasing temperature may alter the suitability of regions for particular crop, and extreme weather events may have severe and unpredictable effects upon harvests. Climate also influences the spread of pests and pathogens, which can diminish and decimate yields, and whole suppression is a permanent battleground in agriculture. As one of the means of biological control of the pest, birds are declining at a faster rate due to harmful radiations and pesticides. It also results in swarming of pests. The threat posed to crop production by plant pests and diseases is one of the key factors that could lead to “a perfect storm” that threatens to destabilise global food security. Currently, it is estimated that between 10% and 16% of the world’s crops are lost due to disease outbreaks. The migratory pest has made several incursions into Rajasthan in the last two decades including a significant one last year. Locusts, last swarmed Madhya Pradesh and Uttar Pradesh in 1993 and have not been seen since 1974 in Maharashtra. But this time, the swarms have spread to Madhya Pradesh, Uttar Pradesh and even Maharashtra.
Desert locusts (Schistocerca gregaria) are short-horned grasshopper species. Generally, in the grasslands, they live a solitary life, not in groups. But when the population density is high, they secrete a pheromone to communicate with each other to assume what is called a ‘gregarious phase’, which means they become aggressive and consume everything in their path. That is when they form swarms and begin looking for high-density food areas. These swarms prefer arid or semi-arid areas for egg laying and nymph development. During periods of low density, the locust inhabits a broad belt of arid and semi-arid land which stretches from the Atlantic Ocean to northwest India. As locust density increases, crowding releases serotonin, promoting rapid movement and a varied diet, spawning mass migration. The migration area of desert locust covers about 30 million square km in nearly 64 countries, including parts of the Indian subcontinent. Locusts are voracious feeders, eating up to their body weight daily. They damage crops by devouring all parts of the plants and also by breaking trees by their sheer weight when they settle down in masses. These insects can fly upto 150 km daily. One square km of a locust swarm contains upto 80,000 adults that, each day, consumes the equivalent of food for 35,000 people. A solitary female lays about 95-158 eggs. Their pheromonal communication informs them of wind patterns as it determines rainfall, which means more vegetation. They move with the winds and follow a definite cycle from the Saharan desert in North Africa, into East Africa- Ethopia, Kenya, Eritrea and parts of Chad. They then move to the Arabian Peninsula and Iran. When they finish the food there, they move over to Pakistan and India, and will also go back to their initial habitats. The current locust swarm is thought to have originated in southern Iran due to the Indian Ocean Dipole, which caused warmer waters to its west and cooler waters to its east. The locust swarm is currently affecting parts of India was responsible for infestation in 2,80,000 hectares across 13 countries prior arrival to India. It entered India through the western state of Rajasthan on 13 May 2020.
In India, locusts have been reported to have destroyed crops in 18 districts of Rajasthan and 12 districts of Madhya Pradesh while crops in Uttar Pradesh, Punjab, Haryana, and Maharashtra are under threat of an attack. This year’s attack is the worst seen in 27 years and it is predicted that crises will increase as we enter monsoon. Locusts impact native grazing species that rely upon grasslands and croplands for survival. Swarms consume everything in their path, leaving behind ruined cropland and barren pastures. While they are not known to impact forests or natural tree cover, their voracious consumption of most species of crop creates food scarcity for native fauna and other species. In Kenya, for example, locust plagues threaten the habitat of the Grevy’s Zebra, a threatened endemic species.
Locust plagues not only rob rural families of their livelihood and income but also take a toll on the lives of women and children. Children often leave their school to help their families recover losses due to locust swarms. Malnutrition was observed in children post-locust plagues, as locusts consumed the same fodder as domestic cattle, reducing the milk quality produced by the cattle and leading to food insecurity and malnutrition.
Management
Potential management techniques for locust pest include using wind as a marker, as wind act as a catalyst in locust dispersal. With the help of metereological studies, the speed and direction of wind flow (>20˚C) can be monitored in India to predict the projectory of locust swarms. Recent events have indicated that locust swarms extended their range towards Maharashtra more so than in previous years. Climate change and its impact on the monsoon is thought to cause range expansion in locust swarms. Species Distribution Modelling (SDM) can show us the relationship between environmental variables (temperature, precipitation, greenness, soil moisture) and the dispersal patterns of locust swarms. It can also aid in predicting regions susceptible to future locust swarms, reducing the potential losses to agricultural communities, and biological control of the pest. Eradication or controlling a pest from an area comes with sets of challenges and include traditional methods of controlling agricultural pests with extensive field monitoring and spraying infected areas with insecticides using Ulta Low Volume (ULV) sprayers. Recently, aerial ULV sprayers mounted on aircraft were implemented and drones being used for surveys and insecticide applications. Desert locusts can be controlled effectively if the control strategies efficiently applied from the beginning stages of the locust. Integrated Pest Management (IPM) suggested the use of efficient biopesticides instead of traditionally used synthetic pesticides like pheromones and mycopesticides. Mating disruption, a direct method to distracts to go after mating, mass trapping of insects and “lure and kill”. The latter two methods use specifically olfactory cues, mimicking either food or sex pheromones to attract pests onto traps. But widely recommended control for pest management were native species of birds and insectivorous mammals, amphibians and reptiles. Introducing the natural predator of the pest in other areas can also effectively control the pest population if no native predators are present.
It is indicated that net damage costs of climate change to crops are likely to be significant and to increase over time.
Anjina Devi, Ph.D Research Scholar, Department of Botany, University of Jammu.