Grasshopper Control in Gardens and Small Acreage
Over 100 species of grasshoppers occur in Colorado and their populations fluctuate from year to year. They may cause serious damage to yards and fields during outbreaks.
Grasshoppers are closely related to crickets and katydids. The table below shows primary grasshopper species found in Colorado.
Feeding injury on an onion.
Two striped grasshopper.
Two striped grasshopper nymphs.
- Grasshoppers are difficult pests to control because they are highly mobile
- All grasshoppers lay their eggs in soil
- During periods when local outbreaks are developing, control usually involves using sprays or baits
|Primary grasshoppers that damage gardens and small acreage pasture areas in Colorado|
|Common Name||Scientific Name||Comments|
|Differential grasshopper||Melanoplus differentialis||Often one of the first grasshoppers found moving into
gardens and one of the largest in the genus Melanoplus.
|Migratory grasshopper||Melanoplus sanguinipes||Often the most damaging species to croplands. Any early hatching species and capable of long migration flight.|
|Twostriped grasshopper||Melanoplus bivittatus||Often the most common species damaging gardens; it migrates
from empty lots, roadsides, and other undisturbed sites. Twostriped grasshopper often
hatches in late spring, a few weeks later than many grasshoppers.
|Redlegged grasshopper||Melanoplus femurrubrum||A widely distributed grasshopper that feeds on many garden plants. It tends to be most abundant in moist sites and is one of the later hatching species.|
|Clearwinged grasshopper||Camnula pellucida||The primary species present in recent outbreaks reported
in areas of the West Slope and around Steamboat Springs. An early hatching grasshopper that restricts feeding to grasses.
All grasshoppers lay their eggs in soil, in the form of tight clustered pods. Dry soils undisturbed by tillage or irrigation are preferred. For most species, eggs hatch in mid to late spring, varying with soil temperature. At egg hatch the tiny first stage nymphs move to the surface and seek tender foliage on which to feed. The first few days are critical to survival. Adverse weather or absence of suitable foods can cause high mortality. Surviving grasshoppers continue to develop over the next several weeks, usually molting through five or six stages, before ultimately reaching the adult form.
Grasshopper Feeding Injury and Impact
Grasshoppers have chewing mouthparts and can defoliate entire plants. Food habits vary between species of grasshoppers, where some primarily feed on grasses or sedges, while others prefer broadleaved plants. Lettuce, carrots, beans, sweet corn and onions are some crops that are favored, while squash, peas, and tomatoes tend to be avoided. Most grasshoppers prefer younger, tender foliage. They can also be a significant pests of field crops and rangeland in years when their populations are extremely high. Surveys of grasshoppers can be very useful in anticipating problems and treating appropriately. Numbers of grasshoppers present in late summer and early fall can be a good indicator of problems the subsequent year. Predicting outbreaks is complex, and the USDA ARS in Montana has excellent resources including a prediction model updated each year.
The most important factors in grasshopper populations are weather-related, particularly around the time of egg hatch. For example, cold, wet weather is very destructive to newly hatched grasshoppers. Many species of blister beetles develop on grasshopper egg pods. Adult robber flies are common predators of grasshoppers during summer and other flies develop as internal parasites of grasshoppers. Many birds, notably horned larks and kestrels, feed heavily on grasshoppers. Grasshoppers are also frequently eaten by coyotes. Grasshoppers may also be affected by pathogens. A fungus (Entomophthora grylli) infects grasshoppers causing them to move upwards and cling to plants shortly before they kill the insect host. Stiff, dead grasshoppers found stuck to a grass stem or twig indicate infection with this disease. A nematode (Mermis nigriscens) also occasionally attacks and develops in grasshoppers. Both the fungus disease and nematode parasite are favored by wet weather. In gardens and small plantings, grasshoppers can be handpicked and squashed. One strategy that can be used in gardens where migration of grasshoppers frequently occurs is to keep an attractive green border of tall grass or lush green plants around the perimeter of the garden to trap insects and divert them from vegetables or flowers.
To be successful, baits and sprays need to be applied during developing stages and concentrated at sites where egg laying occurs. Ability to control grasshoppers declines as they develop and migrate. Alternately, certain baits can be broadcast. Bait formulations are made by mixing the insecticide with bran or another carrier. Baits must be re-applied after rain. Baits containing the protozoan organism Nosema locustae is a biological control option that may be considered for treating grasshopper breeding sites. Because it is selective in effects, only affecting grasshoppers, its use is sometimes considered desirable. There are some limitations to N. locustae baits. Only young grasshoppers are susceptible, and it cannot be used effectively after adult migrations have occurred. Often it is most effectively used in a long-term grasshopper management program, in combination with other controls. The baits are also perishable and are best kept refrigerated before use.
Treatments should be directed at young grasshoppers and nearby vegetation present in breeding sites. At lower altitudes, this often occurs in May; early June may be the optimal time for grasshoppers at higher elevations. Insecticide treatments do not need to completely cover the area since grasshoppers are mobile. Insecticides applied as bands covering 50 percent of the area, or even less, have proved very effective for control of grasshoppers in rangelands.