TWM Special – Desert Locust Upsurge ? – A Common man’s article.


1. What are locusts and how do they differ from Grasshoppers?

Locusts are also members of the grasshopper family Acrididae, which includes most short-horned grasshoppers. Locusts differ from grasshoppers because they have the ability to change their behavior and physiology, in particular their morphology (color and shape), in response to changes in density, when meteorological conditions are favorable. Adult locusts can form swarms that may contain millions or billions of individuals that behave as a coherent unit. The non-flying hopper stage can form cohesive masses that are called hopper bands.

Photo Courtesy: WMO & FAO

They behave as individuals when less in numbers called solitarious phase; when high in numbers, they behave as a single mass and its called gregarious phase. In layman terms, Gregarious definition, If you know someone who’s outgoing, sociable, and fond of the company of others, you might want to call him / her gregarious. Colour and shape are an indication of how they been behaving but may not be a reliable guide as to how they will behave in the future. The phases of Locust is explained in pic below –

Photo Courtesy: National Geographic

2. Where do normally breed and move.

Desert Locusts (Schistocerca gregaria) are always present somewhere in the deserts between Mauritania and India. During calm periods, Desert Locust infestations are usually present somewhere within about 16 million km2 of desert in 25 countries between West Africa and India. During plagues, the number of countries and the size of the potentially affected area doubles, representing about 20% of the Earth’s land mass. Within the recession area, that is, the normal area occupied during calm periods, locusts move with the winds. These bring them into particular zones during the summer (the Sahel and the Indo-Pakistan desert) and during the winter/spring (North-West Africa, along the Red Sea, in Baluchistan (Pakistan) and the Islamic Republic of Iran). If heavy rain falls in successive seasonal breeding areas, the locusts will gregarize and, unless prevented by control, drought, or migration to unsuitable habitats, plagues can develop. Rainfall over 25 mm in two consecutive months is usually assumed to be enough for
locust breeding and development.

When plentiful rain falls and annual green vegetation develops, Desert Locusts can increase rapidly in number and, within a month or two, start to concentrate and become gregarious. Unless checked, this can lead to the formation of small groups or bands of wingless hoppers and small groups or swarms of winged adults. This is called an outbreak and usually occurs within an area of about 5 000 km2 (100 km by 50 km).

Photo Courtesy: WMO & FAO

3. Stages of Desert Locust

The Desert Locust has three distinct stages: (i) egg, (ii) hopper and (iii) adult.

Photo Courtesy: WMO & FAO

EggEggs are laid in pods in moist sandy soil at a depth of about 10-15 cm at an interval of 7–10 days. Gregarious females usually lay 2-3 egg pods having an average of 60-80 eggs/pod. Solitarious females lay 3-4 times having 150-200 eggs in average. The rate of development of eggs depends on soil moisture and temperature, but in general it is about two weeks. No development takes place below 15°C. The incubation period is 10–12 days when the optimum temperature is between 32– 35°C.

HopperAfter incubation is complete, the eggs hatch and wingless nymphs (hoppers) emerge. The rate of development of hoppers depends on temperature. It takes 22 days when the mean air temperature is hot say about 37°C and may be delayed up to 70 days when the mean temperature is below 22°C. In general, it takes about six weeks from hatching to fledging. Hoppers are active throughout the day and will not move more than about 500m or 1 km in a single day. They can be treated throughout the entire day; whereas, swarms can only be treated in the early morning before take-off or in the late afternoon once they have landed.

AdultThe young adult is called a ‘fledgling’ in which its wings are still soft and cannot fly. After a few days, the wings harden and sexual ‘immature adult’ is capable of flight. The immature adult stage is most injurious and capable of long distance travel. Under optimal conditions the adult may mature in 3 weeks and under cooler and drier conditions, it may take up to 8 months. In general, however, it usually takes about 4 weeks before an adult is ready to reproduce. If vegetation dries out, the adults will leave the area and fly with the wind (downwind) in search of green vegetation and favorable breeding conditions. Solitarious adults fly for only a few hours at night while gregarious adults (swarms) fly during daylight. Gregarious adults (swarms) migrate in the direction of the wind (downwind) at the wind speed and can cover a maximum distance of up to about 150 km/day. The direction and speed of the wind determine the displacement of adults and swarms. Before they can take off, a settled swarm must warm up in the early morning shortly after sunrise by basking in the sun. Swarms then fly throughout the day until just before sunset when they land and remain settled on the ground throughout the night.

4.Locust Outbreak, Upsurge, Plague and the past events?

Outbreak: When plentiful rain falls and annual green vegetation develops, Desert Locusts can increase rapidly in number and, within a month or two, start to concentrate and become gregarious. Unless checked, this can lead to the formation of small groups or bands of wingless hoppers and small groups or swarms of winged adults. This is called an OUTBREAK and usually occurs within an area of about 5 000 km2 (100 km by 50 km).

Upsurge: If an outbreak or contemporaneous outbreaks are not controlled and if widespread or unusually heavy rains fall in adjacent areas, several successive seasons of breeding can occur that causes further hopper band and adult swarm formation. This is called an UPSURGE and generally affects an entire region. Eg. 2003-05 and the present one.

Plague: If an upsurge is not controlled and ecological conditions remain favourable for breeding, locust populations continue to increase in number and size, and the majority of locusts behave as gregarious bands or swarms, then a PLAGUE can develop. A major plague exists when two or more regions are affected simultaneously. Eg 1986-1988.


Photo Courtesy: WMO & FAO

Desert Locust plagues have been reported since Phaoronic times in ancient Egypt. There is no evidence that they occur after a specific number of years. During the last century, plagues occurred in 1926–1934, 1940–1948, 1949–1963, 1967–1969, 1986–1988 and 2003–2005. Recent major upsurges were reported in 1992–1994, 1996–1998 and 2003. Locust outbreaks can develop suddenly and unexpectedly in remote, inaccessible areas or in the absence of regular surveys and incomplete data. Recent developments in satellite techniques to monitor rainfall and vegetation have made it easier to detect potential areas of significant locust activity that may require survey and control.

5. What is the threats from Locust Upsurge or Plague ?

The Desert Locust has the potential to damage the livelihoods of one tenth of the world’s population. Recent increases in cultivated areas on the edges of deserts in northern Africa, the Near East and South-West Asia make the Desert Locust a threat to the livelihood, income and food source of local populations. Swarms are often tens of square kilometres in size. A swarm of 1 km2 eats the same amount of food in one day as 35 000 people. A swarm of the the size of Bamako (Mali) or Niamey (Niger) can consume what half the population of either country would eat in a single day.

The last major locust plague, from 1986 to 1988, hit North Africa and the Middle East and many swarms died while crossing the Atlantic; some reached the Caribbean. The Desert Locust plague of 1986–1988, the subsequent regional plague in 2003–2005, drew the world’s attention to the threat they pose to the food security of the affected countries, especially in the developing world.

6. Dont be surprised, FAO issues Locust Upsurge Global Forecast

The current situation remains extremely alarming in East Africa where Kenya, Ethiopia and Somalia continue to face an unprecedented threat to food security and livelihoods. New swarms from current breeding will form from mid-June onwards, coinciding with the start of the harvest. Thereafter, there is a risk that swarms will migrate to the summer breeding areas along both sides of the Indo-Pakistan border as well as to Sudan and perhaps West Africa.

Photo courtesy – FAO

India and Pakistan – Spring breeding continues in southern Iran and southwest Pakistan where control operations are in progress against hopper groups and bands as well as an increasing number of adult groups. As vegetation dries out, more groups and swarms will form and move from these areas to the summer breeding areas along both sides of the Indo-Pakistan border as several waves from now until at least early July. Good rains are predicted during the first half of June along the Indo-Pakistan border that would allow egg-laying to occur. This should reduce the further eastward movement of swarms that have already arrived in Rajasthan, India.

7. Chances of Twin Cyclones in Arabian Sea and more rains at most unlikely places at wrong time which are affected by Locust upsurge.

Global models show twin cyclone in Arabian Sea in coming weeks. The 1st one is expected to be form near Gulf of Eden off Yemen coast and another one is shown with landfall possibilities open right from Oman to Gujarat. Lets take the first one near Yemen, is shown as a meoscale / micro cyclone – small in size. It takes more or less the entire cross equatorial flow winds moisture, if this moves into Gulf of eden, then more rains in the most affected belt in Horn of Africa so more breeding possible. Lets be hopeful that the 2nd system forming pulls this one without giving much rains to Somalia or Yemen. The 2nd one which is much bigger is rain filled one  and is expected cross either from Oman to Gujarat coasts. Lets hope it is not Gujarat or Pakistan, as there will be too much rains as it moves into Rajastahan and will be more ideal for breeding for the next wave. Note-Forecast is subject to change.

8. How India has faced the outbreak in recent years

India is most at risk of a swarm invasion just before the onset of the seasonal monsoon in Rajasthan and Gujarat, in other words, during May and July swarms originating in the Arabian Peninsula and Horn of Africa will reflect in the warning to be received from FAO DLIS. ii. In case of a swarm invasion, LWO should follow the relevant contingency plan.  It has been estimated that in India damage to crops caused by locusts was about Rupees 10 crore during 1926–31 plague cycle. During 1940–46 and 1949–55 locust plague cycles, the damage was estimated at Rs. 2.00 crore each and it was Rs. 50.00 lakhs during the last locust plague cycle (1959–62). Although no locust plague cycles have been observed after 1962, however, during 1978 and 1993, large scale upsurges were reported.

India has a Contingency Plan for Desert Locust Outbreaks, Invasions and Upsurges prepared in May 2019, More recently, there have been several control campaigns that were conducted. Since December 2011, no locust upsurges have taken place.

Photo and extracts  courtesy, Contingency Plan against locust, Government of India

Pesticides used by India against Locusts – Malathion 96% ULV is used in Desert Locust control in India. A buffer of minimum 5000 liters of Malathion 96% ULV will be maintain at specific LCOs from where pesticide can be mobilised for immediate requirement. In 2014, an agreement had been signed with Hindustan Insecticides Limited (HIL) with the provision that the company will supply the required quantity of pesticide. M/s HIL will keep ready stock of 8000 litres Malathion 96% technical reserve and on receiving demand from the Directorate of PPQ&S, will supply the desired quantity of Malathion 96% ULV formulation to the Locust Circle Offices within 7-10 days of the supply order. However, in case of requirement of larger quantity of Malathion 96% ULV, HIL needs 25-30 days to supply the pesticide.

Triggering of the planThe Officer-in-charge, Locust Warning Organization (LWO), Jodhpur is fully responsible for triggering the plan in case of locust invasion, outbreak and upsurge after getting the administrative approval and financial sanction from the competent authority of the Directorate of Plant Protection, Quarantine & Storage, Ministry of Agriculture& Farmers Welfare, Department of Agriculture, Cooperation & Farmers Welfare, Government of India. The plan is triggered based on the information of the current locust situation and expected developments as indicated by the results of national surveys and assessment by the LWO Desert Locust Information Officers, duly supplemented and confirmed by FAO. Execution of contingency plan will start after thorough consideration of locust situation and getting feedback from the surveying teams and desert locust information officer. The plan will be executed within 24-48 hours of its trigger.  The following will be undertaken for Outbreak and Upsurge – 

i. During Outbreak – An outbreak campaign against locally-bred hopper groups and hopper/ adult are likely to occur between June to October depending upon local ecological conditions.ii. The LWO comprising of eleven Locust Circle Office are having manpower, vehicles,control equipments, and personal protective equipment. Each Circle has control potential for treating about 300 ha/day. In case of emergency, pesticide from the storage sites can be mobilized within 6–10 hours and technical manpower from other schemes can be mobilized for undertaking control operations. For additional requirements proposal will be submitted by the locust field units (LCOs) to the LWO, Jodhpur on priority.iii. During locust threat LWO should maintain a buffer stock of 5000 liters of Malathion 96%ULV. Additional quantity 8000 litres, if required may be obtained from M/S Hindustan Pesticides Ltd. (HIL) within a week as per contract between the firm and the Govt. ofIndia, Ministry of Agriculture& Farmers Welfare. For more quantity HIL may require advance intimation of 25-30 days. Therefore, the same should keep in mind prior considering the supply of pesticides.

ii. During Upsurge –  In case of locust upsurge, extra staff and vehicles from other divisions of Directorate of PPQ&S and from State Govt. will be deployed to meet the exigencies. The said practice has already been applied in past operations. Staff to be seconded should be trained in locust control operations from time to time. Remaining untrained staff may be given short training on survey and control operations before deploying them to the fields. Ministry of Agriculture& Farmers Welfare, Department of Agriculture, and Cooperation & Farmers Welfare will make fund requirements to deal the locust upsurge.

Article compiled from various sources – Courtesy WMO, FAO and Contingency Plan of India against locust, Government of India

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