Grasshoppers are insects of the suborder Caelifera within the order Orthoptera, which includes crickets and katydids. They are sometimes referred to as short-horned grasshoppers to distinguish them from the katydids, which have much longer antennae. They are probably the oldest living group of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago. Grasshoppers are typically ground-dwelling insects with powerful hind legs which enable them to escape from threats by leaping vigorously. They are hemimetabolous insects i.e they do not undergo complete metamorphosis and hatch from an egg into a nymph or “hopper” which undergoes five molts, becoming more similar to the adult insect at each developmental stage. At high population densities and under certain environmental conditions, some grasshopper species can change color and behavior and form swarms. Under these circumstances, they are known as locusts.
Grasshoppers are voracious feeders, consuming approximately one-half of their body weight per day. Both adults and nymphs cause damage by chewing on the leaves and stems of plants, and if infestations are severe, may defoliate entire fields. It is estimated that grasshoppers consume up to 25 percent of the available forage in the western United States annually.
The injurious species of grasshoppers are all alike in their cycle of development. Eggs are deposited in late summer in elongated masses or pods inserted in the soil. These pass through the winter, and on hatching in the spring, the young seek food in the immediate area. As they increase in size and food becomes scarce, migration to other food sources takes place. After molting 5 or 6 times, during a period of 40-60 days, the adults appear and continue feeding until cold weather kills them.
Grasshoppers are general feeders on grasses and weeds and often move to cultivated crops. Crop damage is likely to be greatest in years when dry weather accompanies high populations. Drought conditions reduce natural vegetation, forcing grasshoppers to move to cultivated crops. Several species of grasshoppers feed on soybean foliage. The damage that grasshoppers cause appears as round to ragged holes in the leaves. These ragged holes extend in from the leaf margins and between the veins. Grasshoppers may also feed on and damage soybean pods, often chewing through the pod tissue into the seed. This may be a serious problem in dry years.
Mostly grasshoppers prefer young green plants, especially lettuce, beans, corn, carrots, onions, and some annual flowers. Squash and tomatoes are among the vegetables grasshoppers least favor. Grasshoppers have chewing mouthparts that remove large sections of leaves and flowers, sometimes devouring entire plants. Garden damage is usually limited to a few weeks in early summer immediately after range weeds dry up. However, during major outbreaks grasshoppers will feed on almost any green plant, and damage may occur over a considerably longer period.
Let us look at some recent news articles pertaining to the damage caused by the grasshoppers.
Voracious, gregarious locusts
January 31, 2017, The Hindu, India
A locust is a grasshopper, which in its swarming phase can devastate thousands of acres of crops — to the extent of putting humans into famine and starvation. History is fraught with its notorious acts.
In solitary phase, locusts are just another grasshopper, with short horns. Taxonomically, there is no difference between a grasshopper or a locust, it is in their behavior, that they exhibit differences. They are also called acridid and commonly seen in swarms in different parts of the world, on all continents except Antarctica.
They are highly migratory and are classified into ten subspecies. Species such as the Senegalese grasshopper and the African rice grasshopper have been observed to display locust-like behavior on crowding.
Destructive behavior
When conditions are right, the harmless solitary locust undergoes a rapid set of changes. When there is a dramatic vegetation growth followed by drought in an area, the locusts start to breed more. The scores of wingless nymphs become swarms of winged adults. They together become gregarious (tending to associate with others of one’s kind and growing in a cluster) and migratory. They fly as a thick patch of swarms, devouring the crops on their way. They also cause huge damage. The adults consume most of the green vegetation.
They migrate in millions and cause damage through infestation. They have been a major cause of concern in agriculture that they have formed plagues since prehistory. In 1915, swarms of locusts stripped areas in Palestine and Syria from March to October, putting these places into a deep food crisis.
More recently, in 2013, Malagasy migratory locust devastated Madagascar, following a cyclone in February. The nation saw a surge in locust population and soon the insects occupied 50 percent of it. The authorities changed the situation to plague status.
Swarm of grasshoppers takes over Central Australia
January 24, 2017, ABC News, Australia
Swarms of insects have descended upon the Central Australian outback after recent rainfall.
In particular, large amounts of yellow-winged grasshoppers have populated the area, both in Alice Springs and surrounding areas.
Chris Adriaansen, director of the Australian Plague Locust Commission, identified the insect as a grasshopper species.
“They’re not a locust species, they’re a grasshopper species,” he said.
“Yellow-winged grasshoppers are fairly widespread across Australia, and the population rises and falls quite dramatically with weather conditions.
“Given the rainfall that’s been in Central Australia four or five weeks ago, the population has just burst forth.”
Mr. Adriaansen said local grasshoppers will be looking to eat vegetation, unlike the Australian plague locusts which feed on grass species and grain crops.
“When they’re in numbers obviously they can create a level of damage,” he said.
Today food scarcity is one of the major issues that the world is facing. About 11.3 % of the world population is hungry. Thus we cannot afford this significant amount of crop damage caused by pests like a grasshopper. There is an urgent need for a sustainable solution.
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