Locust plagues

Locust plagues decimate everything in their path. Related to grasshoppers these insects are one of the most destructive pests on earth.

Plagues of locusts devastated crops, pastures, orchards and entire countries and continents since mankind began keeping written records. Passages in the Bible even make reference to these destructive outbreaks. Once locusts are compelled to swarm they amass quickly and in such great numbers that they actually blot out the sun while in flight. During a migratory “plague” one swarm can be made up of millions, sometimes billions of insects. After homing in on a food source, the entire swarm lands and then proceeds to eat everything in its path, devastating the area within a matter of hours. Then the swarm rises up as a single massive unit and moves on to the next field or orchard. Swarming locusts can cover distances of several hundred miles in a 24 hour time frame.

Until recently scientists believed that locusts were an insect group unto themselves but researchers have found that they are a species of “short-horned” grasshopper, so named because of their shorter antennae. Grasshoppers are plant eating insects and found on all continents of the world except the Arctic regions. Cicadas and katydids also fit this classification. While most grasshoppers feed on plants, a very few are carnivores, eating carrion or catching smaller insects. During an infestation grasshoppers incur considerable crop damage, grain, corn, cotton, and fruit and vegetable crops their main targets. Natural predators like birds, beetles, snakes and small mammals normally keep numbers under control, as do applied chemicals. Like most beetle species, however, grasshoppers tend to build up an immunity to insecticides over time.

Grasshoppers grow to a size of about 1 inch and are able to jump close to 2 feet in a single bound. Their bodies are divided into 3 distinct segments: head, thorax and abdomen. They have six feet and four wings and their stiff outer shell is called an “exoskeleton. Grasshoppers also come equipped with five eyes. Two larger "compound” eyes reside on either side of the head and inside are thousands of tiny lenses,allowing the insects to see in all directions. The other eyes are located on the antennae. What purpose they serve remains undetermined.

Female grasshoppers lay eggs in large numbers in late summer and early autumn in clusters of 2-100, and after lying dormant over winter the young emerge in the spring. These “nymphs” are born wingless and require about 2 months to mature into adults. They are able to change colour to blend in with their habitat and avoid predators. The nymphs spend much of their time eating and shedding 5-6 sets of exoskeletons. Wings develop after this “molting” process and the new adults are finally ready to fly.

Locusts closely resemble grasshoppers in appearance, yet are larger, measuring around 2 inches in length. What makes them different from their grasshopper cousins is that locusts can actually go into two behavioural states, depending on population densities and environmental conditions. Normally locusts remain in what is called a “solitary” phase. But if favourable breeding conditions cause more young to hatch than usual, resulting in overcrowding and scarcity of food, or the locusts migrate to regions where the habitat is unsuitable, the insects will go through what is called a “phase change”. This second state is called the “gregarious” phase where the locusts become agitated, begin to gather in very large numbers and finally evolve into a single migrating swarm, or plague.

Once a plague of locusts breaks out there is little that can stop it. A single band is sometimes miles wide and besides blotting out the sun will interfere with land and air travel, clog machinery like car radiators, not to mention devour an entire country’s food supply in a matter of days. Like grasshoppers, different species of migratory locusts are found in many regions of the world from the deserts of Australia and Africa to the plains of the United States and Canada. Since locusts travel on wind currents it’s not uncommon for swarms to cross oceans, jumping from one continent to another. Consequently these insect pests continue generating billions of dollars in crop losses around the globe.

The Anti-Locust Research Centre, established in 1945, keeps close tabs on locust outbreaks and carries on extensive research in an effort to monitor and control the pests. Fortunately massive plagues happen only sporadically. Fall ploughing to destroy eggs, poison bait, and dusting and aerial spraying are some of the more widely used methods to deter possible outbreaks. Over the last ten years researchers from various countries have been working together to find a more sure-fire and environmentally friendly way to control the ravaging locust plagues. So far they’ve had the most favourable results using a fungus that attacks and degrades the locust’s internal organs, killing the insect after 2-3 weeks. Further testing of the fungus and other locust control methods continue.