About GrasshoppersOne of the most recognizable features of grasshoppers is the songs they make by either rubbing pegs on their back legs together, or clattering their wings together while they are in flight. Some just rub their wings together and others do not produce any sound. The main species of grasshoppers that cause the most concerning issue with crop loss is the short horned grasshopper. In North America alone there are more than 600 species of grasshoppers. As a result, a lot of varieties and subgroups are usually referred to as “grasshoppers”. There are a few species of grasshoppers that are considered to be of economic importance. This means the species under this label that have ideal food and weather conditions, reproduce quickly and can cause severe crop damage. Grasshopper Reproduction and Life Cycle The life cycle for all types of grasshoppers is essentially the same. Two weeks after mating, female grasshoppers look for a suitable site to lay her eggs. After a place is picked, the female grasshoppers bore a hole with her stomach and will lay a cluster of orange to cream coloured cylindrical, slightly bent eggs. After birth she deposits a foamy discharge over the eggs. This discharge then hardens to form an egg pod. There is a great variation in the number of eggs per pod, ranging from 8 to 150 eggs. Typically grasshopper species that lay fewer eggs per pod produce more pods than the females who put a lot of eggs per pod. Under desirable environmental conditions, one female can produce an egg pod every 2 to 4 days. On average a female grasshopper reproduces more than 250 eggs in her lifetime. The development of the embryos starts once the eggs are laid and continue until the unfavorable environmental conditions of the fall and winter come. The eggs lay dormant until the soil temperature gets to about 10°C during the spring months and will continue to grow and then eventually hatch. Nymphs are newly hatched grasshoppers; they are about 5mm in length and in similar appearance to fully mature grasshoppers, minus their wings. Almost right after birth the young grasshoppers start feeding on most green vegetation that is close to their hatching site. The development of nymphs takes about 5 to 6 stages to become a fully mature winged adult. If there is good weather that is warm but not too wet with lots of vegetation, this process will take roughly 35 to 50 days. Overall, adult females are marginally bigger than males. Depending on the species of grasshoppers, their annual life cycle may vary. The variation between species could be the over-wintering as nymphs or over-wintering as adults. Some varieties of grasshoppers take 2 years to complete their life cycle. These particular varieties of grasshoppers are responsible for the reports of grasshoppers in early spring and late fall. For most grasshoppers, their annual life cycle starts in late summer or early fall of the preceding year, and over-wintering as eggs. Grasshopper Identification and HabitatIdentification All members of the grasshopper family can be characterized by a gradual change in form and size as they develop chewing mouth parts, large and powerful hind legs for jumping, slender bodies and wings that fold lengthwise. In general, grasshopper’s bodies are stick-like to round with wide shoulders and hard, tapering stomachs. They have segments behind their heads that drape over each side forming large lateral lobes. Each grasshopper has a pair of antennae that are thread-like and can vary from very short to longer than their body. For the most part grasshoppers have large, round eyes that are well separated. Depending on the variety of grasshopper, they may have one or two pairs of wings. Their forewings are hardened, leathery, are usually see-through or cloudy in colour and are held tent-like or flat over their bodies. Their hind wings are typically larger than the forewings; they are membranous and fold like a fan. Most grasshoppers have six slender legs with spines covering them. Their back legs are in similar shape to chicken drumsticks, giving grasshoppers the ability to jump 20 times the length of its body. Varieties Grasshoppers are divided into two main subgroups according to the length of their antennae, also known as feelers or horns. The subgroups are the long horned grasshopper or katydids and the short horned grasshopper that are typically called locusts. Long horned grasshoppers, also known as Tettigoniidae, are green in colour, have long wings and live in trees, shrubs and bushes. These include cone-headed grasshoppers, katydid and meadow grasshoppers. The exception to this is the shield-backed grasshoppers, which includes the coulee and Mormon crickets. They are gray or brown in colour, living along the ground or in low vegetation. They are typically wingless or have very small wings. All long horned grasshoppers have hearing organs known as tympanum that is located on their front legs, along with antennae that are as long or longer than their bodies and wings that cover their bodies in different shapes. To attract females, male grasshoppers run their wing covers together. Each species of grasshopper has its own song. There are 3 types of short horned grasshoppers. Each type has distinguishing characteristic that makes it fairly easy to classify them. It is crucial that farmers know and recognize these characteristics if they want to provide effective control over grasshopper infestation. The spur-throated grasshoppers This particular species of grasshoppers can be identified by the knob or tubercle between their front legs. There are 3 varieties of the spur-throated grasshopper that is economically important. They are the packard grasshopper (meanoplus packardii), migratory grasshopper (Melanoplus sanguinipes) and the two-striped grasshopper (Melanoplus bivittatus). Adult packard grasshoppers are bark yellow or gray in colour with two light coloured stripes running from behind the eyes along its back. The last two segments of their back legs are blue-green in colour and prefer light textured soil with slim grass coverage. The migratory adult grasshoppers are brownish to yellow in colour with their back legs marked with black bands. The two-striped grasshoppers are greenish or brownish in colour with brown or black markings. Extending from the back of their eyes to their wings are two pale stripes with a solid black strip on their back legs. Two-striped grasshoppers can typically be found in heavier textured soil. The band-winged grasshoppers The main characteristics for band winged grasshoppers are their hind wings that are typically bright in colour. When they are in flight they can produce a cracking sound with their wings. The most noticed member of the group is the Carolina grasshopper which has black wings, with a pale border around them. The most economically important species for this variety is the clear-winged grasshopper (Camnula pellucida). These grasshoppers are brownish to yellowish in colour, and have clear wings with dark patches. They have two stripes that start in the middle of their bodies and run to the top of the forewings. - The slant-faced (also called tooth-legged) grasshoppers
This particular group of grasshoppers is not as popular as the first two types of grasshoppers. They are quite harmless, go quite easily unnoticed by observers and typically do not need to be controlled. They have slanting to almost horizontal faces, clear back wings, sword-shaped or cub-like antenna and a broad, rounded back half.
Habitat Reduction of yield can happen even with a moderate infestation of 10 grasshoppers per square metre; they can eat 16-60% of the available crop. The extent and type of damage that is done is dependent upon what the crop is, how well it is growing, how many grasshoppers are present and if there is cultural and chemical control methods being used. Areas that have drier climates are more prone to a recurring problem of grasshopper infestations but they can be found nearly everywhere in the world, excluding extremely cold regions. Grasshoppers are herbivores, eating only specific kinds of plants, while other will eat any plants they can find. Over time cereal grains have had the majority of damage done to them; other crops can be seriously affected as well. These crops affected could be alfalfa, canola, clover, cotton, lentils, lush foliage, peas and winter wheat. Depending on the variety of grasshopper, they like to live in weedy grain fields, pastures that are cultivated and hay fields. Large numbers of grasshoppers can be found in crops that are across from stubble fields, especially if they have been cultivated in late spring. Grasshoppers that have hatched in crops that have been seeded in stubble fields feed on the young seedling, damaging the leaves and going unnoticed until major damage has been done. Grasshoppers Control MethodsUnderstanding the amount of control needed and proper timing of control methods for the year can be somewhat predicted if you understand how the weather effects grasshoppers reproduction. The temperature, snowfall and rainfall are very important environmental aspects that can determine the severity of infestation by grasshoppers. A warm fall will result in more female grasshoppers laying more eggs. It will also allow the embryos to develop further before the winter and colder weather settles in. Additional egg development in the fall will lead to a much earlier and more even hatch the following spring. On the other hand, a very cold fall and winter with minimal snow leads to many of the grasshopper’s eggs freezing. For some species of grasshoppers eggs that are exposed to subzero temperatures for two long will kill up to 90% of the young. For the most part, grasshoppers tend to lay eggs in areas where snow fall is thick; this keeps the ground more insulated, thus keeping the eggs alive. Also, an extremely dry fall and spring can limit the development of the embryos with the eggs. If there is a hot spring, it will stimulate the eggs to develop fast and hatch early. Cool spring will do the opposite and slow their development down. Cultural Control The best method available for controlling grasshoppers is a cultural control method, which is usually the least expensive process. They merely involve good management and good timing of normal operations that need to be done in the production of crops. A farmer is able to reduce the number of grasshoppers directly, or at least limiting or stopping their ability to reproduce, by simply modifying their environment at critical periods of their life cycle. The general principle of cultural methods used in controlling grasshoppers starts with early seeding of crops, good crop rotation and tillage. Early seeding means that your crops should be planted as early as possible. Older plants that are more established have a much easier time withstanding grasshoppers compared to younger plants that are not as established. However, early seeding will not totally prevent or guarantee that the crops won’t be damaged, but it will reduce the severity of damage that will occur and give farmers time to apply the appropriate insecticides. Tillage, also known as chemical fallowing, helps manage the population of grasshopper by removing the plants that young grasshoppers feed on. It is recommended to eliminate all green growth in fields in early spring before grasshoppers have hatched. If there is no food available once they have hatched, young grasshoppers will not be able to survive. Tillage at this time will also destroy the eggs of the grasshoppers or expose them to natural enemies such as birds. Since female grasshoppers prefer firm soil to lay their eggs in, tillage will provide an unsuitable environment for them. It is important to know that excessive tillage can be harmful to the soil by reducing its moisture levels and increasing the risk of erosion. Grasshoppers do have natural enemies who attack them in egg, nymphal and adult stages of their life. Predators that eat grasshoppers in the egg phase of life are bee flies, blister beetles, crickets, ground beetles and other insects. Some adults of these insects such as the field cricket can destroy up to 50% of the egg population in one area. Natural enemies of nymphals and adult grasshoppers would be birds, spiders and rodents. Chemical Control Chemical control is also another method that can work in reducing or eliminating grasshoppers. Be sure to carefully read the label for cautions and proper application. It is extremely important to never spray on days that are windy. Over the past few years, diflubenzuron, has been the preferred chemical to control grasshoppers. When diflubenzuron comes in contact with grasshoppers, it hardens the exterior of their body causing them to die. The advantage to using this chemical is that it is not toxic to adult insects like birds, bees and mammals. It is; however, toxic to immature aquatic insects. A few other pesticides that work to control grasshoppers are carbaryl and malathion. These chemicals need to be applied at very low volumes when sprayed. The down side to using these two pesticides in a liquid form is that they cannot target specific areas and may injure beneficial insects. That is why carbaryl and malathion are not frequently used in large infestations, but for smaller areas needing to be controlled. These chemicals are not approved to be used near any body of water. Sources http://www.agriculture.gov.sk.ca/Default.aspx?DN=626d78ef-2444-4fae-98fc-95e05d88e759 http://www.canadiangeographic.ca/kids/animal-facts/grasshopper.asp http://insected.arizona.edu/ghopperinfo.htm http://australianmuseum.net.au/image/grasshopper http://www.britannica.com/animal/long-horned-grasshopper http://www.ext.colostate.edu/pubs/insect/05535.html http://www.blm.gov/wy/st/en/programs/weeds_pests/grasshopper.html http://www.agf.gov.bc.ca/cropprot/grasshopper.htm |