Year of the Locust

by Bill Coffin

Year of the Locust

They attack by the millions, massed so thickly they blot out the sun. Endlessly voracious, they reduce entire lush croplands to barren ruin in hours. And once they take flight, they are almost impossible to stop. They are locusts, the creatures of Biblical plague. They are having a banner year in 2005, and that spells disaster for farmers and agricultural businesses from western Africa to eastern Australia.

Locust outbreaks are nothing new. Every 10 to 15 years, western Africa experiences a major locust plague brought on by periods of extreme rainfall followed by severe drought. Afterwards, locust hatchlings spring out of the ground in groups so large that when they scurry across the earth en masse they resemble moving water.

Mauritania is the hardest-hit nation of any currently experiencing locust outbreaks, and it is expected to lose up to 40% of its annual crop yield due to these winged pests. (It is important to note, however, that in other regions hit by locusts this year, the damage to crops has been much lower so far, usually less than 5% of total yield.) From there, the swarms have already begun to spread, as they always do, across northern Africa and even as far north as Portugal and the Canary Islands in the east and Israel and Cyprus in the west. It could get worse; African locusts are known to swarm as far as Pakistan.

The damage in Europe and the Middle East has thus far been negligible, largely because the locusts were too exhausted to eat by the time they landed. Though the arrival of the swarms was a harrowing spectacle, locals responded with pesticides and in some cases, flamethrowers, destroying any insects that had not already been blown out to sea. Still, the locusts’ migration season is not yet over, and they may yet wreak substantial damage across northern Africa and elsewhere. At the very least, Mauritania will face agricultural devastation courtesy of the worst locust outbreak in nearly a generation.

Halfway across the world, Australia faces a record-making plague of its own. The states of New South Wales and Victoria are at the forefront of that country’s recurring locust problem. Australian locusts strike about once every five years, and they can fly farther in one day than any other locust species—almost 700 km (435 miles) if the winds are right. What is worse, the distance between locust breeding grounds and agricultural lands is shrinking as once-desolate outback land is being irrigated and transformed into lucrative crop acreage. This increases the challenge for farmers and authorities tasked with deterring locust outbreaks in a space some two million square kilometers in scope and containing them before they hit Australian croplands.

Especially at risk is the booming Australian wine industry, which has become an popular import in the United States and elsewhere. One visit from the plagues could wipe out an entire years’ production overnight.

Africa and Australia are not the only places currently facing locust problems. In fact, the only inhabited continent without a major locust problem is North America, though that was not always the case. In the late 1800s, western pioneers were often troubled by the Rocky Mountain locust, which in 1875 formed the biggest swarm on record consisting of trillions of individual insects and stretching some 1,800 miles from Texas to North Dakota. The swarm blackened the sky and devoured everything green in its path causing $116 billion in damages in today’s dollars, dwarfing the insured losses from Hurricanes Andrew and September 11 combined. The locusts’ weakness was that it had a single breeding area—the river valleys of the Rocky Mountains—which were later settled extensively by the same pioneers who had been eaten out of house and home by the insects a few years earlier. Within a few years of the 1875 plague, these settlers unknowingly destroyed the locust’s sole breeding ground through extensive plowing and cattle grazing, driving the species into extinction. No large locust outbreak has since occurred in North America.

The demise of the Rocky Mountain locust is the only known case of a major pest species destroyed by people. And even this was an accident. In Africa, Australia and anywhere else facing the scourge of locust swarms, luck is no remedy. Innovative and aggressive risk management is called for to prevent catastrophic damage from occurring each and every time the locusts drop in for dinner.

Know Your Enemy
To properly fight locusts, it helps to know a bit about them. The charming fellow gracing the cover of this magazine is the common desert locust, and is the world’s principal migratory species, both in terms of the damage it causes and its range. The desert locust can affect an area that covers northern Africa, the Middle East and southwest Asia. In particularly bad years, desert locusts may impact up to one in 10 humans, worldwide. Other species exist in Australia, South America and elsewhere, and they are capable of causing damage similar to their African counterpart.

A single female locust lays up to 80 seed pods, which lie in the ground for up to eight weeks before hatching. Only 25% of these eggs will even hatch, but every new generation of locusts is larger than the last. Locust hatchlings are small and wingless creatures known as “hoppers.” They quickly grow into adulthood, eating up to three times their body weight each day as they do. Once they are fully grown, they develop wings and can fly, greatly increasing their range and destructive capability. At this point, they eat their body weight daily and their lives are an endless search for food. Locusts live up to six months, and most do not survive their migrations. But those that do mate before perishing. 

Locusts are actually solitary and docile creatures, but under the right conditions, they undergo a phase change in which they change color, get larger and become more aggressive. This is when they begin to swarm and become a big problem. Scientists have discovered that what triggers a locust’s phase change is frequent contact with the hairs on the back of a locust’s leg, something that typically happens when locusts are overcrowded and bump into each other frequently.

Swarming conditions are a result of periods of high rainfall in breeding areas followed by periods of extreme drought. The result is that after the rains, large locust populations develop, which then crowd together on dwindling food supply areas during the subsequent drought. Crowded together, the locusts trigger each other’s phase change and become swarmers. When swarming females lay their eggs, they include a chemical that ensures the offspring are born as swarmers. The result is a locust outbreak, or plague. Both Mauritania and Australia are prime examples of this. Mauritania recently had a spectacular rainy season—so spectacular in fact, that racers in the Dakar road rally plowed through mud puddles instead of racing over sand dunes. And in the Australian outback, large ponds and lakes had formed where normally there is only baked earth. In both places, the rain stopped and the water eventually dried up. The locusts followed soon afterwards.

Locusts are susceptible to temperature, however. Below 68F/20C, locust eggs cease developing, and locusts themselves become sluggish and incapable of flight. But by the time it gets this cool, the swarms have done their damage. 

Maintain the Rage
The key to limiting the locust damage is early action, says Laury McCulloch, director of the Australian Plague Locust Commission (APLC). Based in Canberra, Australia, this small government agency plays a vital role in protecting Australian agriculture from locust plagues. It conducts control campaigns nationwide against locust populations that may potentially affect rural industries. It also monitors populations, predicts outbreaks and researches locust biology and control. McCulloch, a 20-year veteran of locust wars in Australia, Africa, Asia and South America is part of the APLC’s small staff of around 18 people. Half of them are stationed in Canberra. The others are stationed at field posts in New South Wales and Victoria, where they can swing into action the moment a locust outbreak is detected.

Because the land areas where locusts breed are so large, McCulloch says that the APLC relies on farmers and agribusiness to help in early locust prevention efforts. In fact, he says, the government of New South Wales requires farmers to patrol their lands and make a best effort to detect locust plagues and call the authorities as soon as locusts are discovered. Despite this, McCulloch acknowledges that farmers generally cannot be expected to patrol their land constantly, so the APLC also monitors weather data (for rainfall patterns that would encourage locust outbreaks) and uses a variety of devices that can help detect the presence of hoppers. One such device is a light trap—a large dish of water fitted with a bright light that attracts locusts. Checking these traps regularly lets farmers and the APLC know if a locust outbreak is underway in the area.

The APLC also deploys field survey teams that patrol areas likely to have locust hatchlings. When locusts are discovered, pesticides are deployed to destroy the swarm (often by airplane). Acting quickly, the APLC can contain a locust outbreak. But since locusts generally do not form a single swarm but hundreds of smaller ones, McCulloch must keep a constant vigil for fresh signs of the enemy. Such persistence pays off: a study conducted by the APLC in the 1980s shows that locust prevention cost around $5.3 million per year but prevented nearly $152 million in crop losses, for a cost-benefit ratio of about 1:30. McCulloch suspects that ratio has since climbed to 1:35 or 1:40 as Australian cropland has expanded deeper into the outback, producing more lucrative harvests.

One recent news story from New South Wales credited tough locust prevention with saving up to $683 million worth of crops and pastures this season alone. NSW Primary Industries Minister Ian Macdonald noted that such success could backfire, however, if farmers became complacent and failed to check their properties as rigorously as they ought to, now that their winter crops have been harvested. “We need farmers to maintain the rage and help us control these pests,” he says.

In New South Wales, for example, control campaigns are handled by three different groups: the APLC, the NSW Department of Primary Industries (NSW DPI) and rural lands protection boards (RLPBs). The NSW DPI organizes statewide control campaigns and monitors plague locust populations. RLPBs monitor and report outbreaks, organize landowner control of hopper bands and adult swarms, and distribute pesticides. The Rural Lands Protection Act 1998 gives RLPBs the responsibility to ensure that landholders keep suppressing and controlling plague locusts. RLPBs also help organize aerial control activities.

According to the NSW DPI, the aim of a control campaign is to contain the outbreak at the nymph stage, preventing the locusts from breeding and migrating. When locusts first become mobile as hoppers, they travel on the ground in waves or “bands,” and can be controlled by applying pesticide through mobile sprayers or by applying bands of pesticide on the ground for the locusts to cross and come into contact with. This is where landowners can best get involved, by reporting the presence of outbreaks to their RLPB, and later, by applying pesticide to the locust populations. Since most pesticides often have dangerous side effects either to other life forms or the environment, it is important for landowners to use pesticides approved and provided by their RLPB.

By the time locusts get more mobile  and actually begin to swarm, they will require aerial spraying, which also may be used for hitting swarms of outbreaks in remote areas beyond the reach of landowners. That is where government agencies such as the NSW DPI or the APLC get involved, since they have the equipment for aerial spraying that most landowners lack.

License to Kill
The main weapon against locusts is pesticide, and lots of it. Various kinds have been used (and abandoned) over the years, but in Australia, the three most commonly used control agents are the insecticides fenitrothion and fipronil, and the biological control agent metarhizium.

Fenitrothion. This is a fast-acting “knock down” agent so named because it kills locusts immediately. It is used in situations where the locusts will inflict serious harm if they are allowed to live any longer. Fenitrothion is an emulsifiable concentrate diluted in water and applied directly to locusts. This chemical causes little environmental harm, but it is extremely toxic to aquatic wildlife and bees, so buffer zones must be established before its use around areas such as natural waterways, tanks and dams, beehives, human dwellings and neighboring properties.

Areas where fenitrothion has been used must also be withheld for a period of one to two weeks from grazing, cutting for stock feed, harvesting or slaughter in order to avoid contact with dangerous residue. Fenitrothion should be applied on nymphs (young locusts) at their second or third instar (developmental) stage, when they are most closely banded together. The agent should be applied directly onto the nymphs about one swath-width ahead of the band, at least five meters (16.4 feet) in front, and then work back through the nymph band from the dense leading edge. Most types of spraying or misting equipment can be used for application, but boom sprays are the most suitable, followed by air-blast machines (misters) and boom jets that apply 50 to 200 liters per hectare (13 to 53 gallons per 2.47 acres). High-volume gear, such as orchard sprayers should not be used, as they are not efficient.

Fipronil. This is a residual control agent that takes effect slowly either by contact or by ingestion. It is designed to be applied to pastures and croplands or as a barrier treatment. Like fenitrothion, fipronil is toxic to aquatic wildlife and bees, requiring a buffer zone. Treated areas must also not be used for one to two weeks afterward for grazing, cutting, harvesting or slaughter to avoid residue. Like fenitrothion, fipronil should be applied when nymphs are at their second or third instar stage and applied directly in the same manner as fenitrothion. When used as a barrier treatment, fipronil should cover foliage in a strip at least 25 meters (82 feet) wide, ahead of advancing nymph bands. 

Metarhizium. This fairly new biological control agent is suitable for use in environmentally sensitive areas, such as those adjacent to waterways and in organic farming areas. Metarhizium is derived from a naturally occurring Australian fungus that kills locusts and grasshoppers by germinating on their bodies. It takes eight to 18 days to work, however, so it should only be used on nymph populations. Metarhizium is available as a suspension concentrate and has a limited storage life. The agent should be used on second or third instar nymphs and applied in a similar manner as fenitrothion.

When spraying pesticides, the usage directions, warnings and disclaimers all merit close study prior to use. New South Wales requires all users of locust insecticides to conduct, review and record a risk assessment of a planned spraying beforehand. Personnel likely to be exposed to high levels of fenitrothion, example, should have their cholinesterase levels monitored; atropine tablets should be kept on hand in the event of acute overexposure. According to use, personnel applying any locust pesticide must wear the appropriate personal protective equipment, such as fully buttoned cotton overalls, full-face respirators, elbow-length PVC gloves and a washable hat. All chemical use must be officially documented and kept on record for at least three years, subject to audit by the NSW Department of Environment and Conservation.

The NSW Department of Environment and Conservation is the only department that licenses aerial applicators of pesticide, and under the NSW Pesticides Act, those involved in the decision to apply pesticides aerially share the legal responsibilities of the act. This includes fines for violating buffer zones and damage caused by off-target drift.

Any chemicals used must be properly disposed of, and their containers sufficiently rinsed and cleaned. Containers must be triple-rinsed or pressure rinsed prior to disposal, since even small amounts left inside are concentrated and highly toxic. Any remaining agent should be deposited in a disposal pit specially dug for the purpose, although the best solution is to use the entire agent on the locusts.

Chemical Dependency
Once a swarm has reached adulthood, no amount of spraying is likely to seriously hinder the swarm’s movement or ability to damage crops. Moreover, Pesticide Action Network UK, a London-based locust control organization, suggests that the widespread use of chemical agents may be overrated. For spraying to be truly effective, locusts need to be hit where they hatch, and in Africa, this generally is in remote, war-torn areas that are often thick with land mines. In Australia, this area is the outback, which is smaller than the desert plains of Africa but still big enough for hatchlings to hide in plain sight.

Then there are environmental concerns, especially in Africa, where people and livestock are endangered by the more than 20,000 tons of surplus and outdated pesticide stocks present in the area. Alternative pesticides are being developed, such as diflubenzuron and trifluormuron, which prevent locusts from molting and essentially suffocate them in their own outgrown exoskeletons. Fungicidal agents such as metarhizium also may be more effective when coupled with satellite positioning technology that will help pinpoint swarms more quickly.

But there are methods in development even more far-reaching than that. One particularly promising solution scientists are working on is to somehow inhibit the nerves that carry the signal from a locust’s hind legs to its brain that it is time to undergo a phase change. If locusts can be prevented from becoming swarmers, the problem can be stopped at the source.

Such relief would be welcome news for the embattled farmers of Africa and Australia, who have taken a stoic view of their unwanted guests. Many see locusts as just another natural hazard, like drought, hail or rainstorm, and consider fighting the locust plagues to be a bit like trying to outrun lightning.

But as the disappearance of the Rocky Mountain locust shows, even something as large and recurring as locusts need not always be a risk to manage. Agriculture might just win the war against locust outbreaks. Until then, however, these plagues will remain a cost of doing business in the warmer zones of the world. For those hit hardest by the locusts, the cost is usually too high to bear.

Bill Coffin is the editor in chief of Risk Management Magazine.

Reprinted from Risk Management Magazine.
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