Grasshoppers
Grasshoppers chew large, ragged pieces out of leaves and flowers, and in bad years can strip lettuce, beans, sweet corn, carrots and onions. They hatch in spring from egg pods laid in undisturbed soil. Most gardens are invaded from outside, from grassland, weedy margins and uncultivated ground. That makes them hard to control in a garden. Protect the plants you care about with row covers or metal screening, keep poultry if you can (they may also peck at some plants), and hand-pick. The biological bait Nosema locustae, sold as Semaspore and formerly Nolo Bait, works only on young nymphs and takes weeks: the Nolo label says death begins 3 to 6 weeks after feeding. UC IPM says it is not likely to be effective in California home gardens. See the Nosema page for the evidence.
Melanoplus differentialis on a bean leaf, with fresh feeding along the margin. Photo: pending.
Identification
Grasshoppers have hind legs with greatly enlarged femurs for jumping, and short antennae, which separate them from crickets and katydids (UC IPM). California alone has more than 200 species, and UC IPM names the devastating grasshopper (Melanoplus devastator) and the valley grasshopper (Oedaleonotus enigma) as the most widespread and destructive there. In the eastern and central US, Kentucky Extension picks out three common Melanoplus species. The red-legged grasshopper has red hind legs with black stripes. The two-striped grasshopper has a narrow yellow stripe running back from each eye. The differential grasshopper has chevron-like black marks on its hind femurs.
The nymphs look like small adults, with non-working wing pads instead of wings (Kentucky). They are what the biological bait targets, and UC IPM says small nymphs are easier to control than larger ones, while adults are very difficult. Adults can fly long distances: UC IPM says adults may fly 15 or more miles a day in large swarms during migrations, which come when populations are high and forage runs out.
Easily confused with
- Crickets and katydidsAlso a pestCrickets and katydids have long, thread-like antennae; grasshoppers have short antennae and greatly enlarged hind thighs.
Damage symptoms
Grasshoppers have chewing mouthparts and remove large sections of leaves and flowers (UC IPM). They move in from grassland and uncultivated ground (UC IPM), and Kentucky Extension says they are generally a problem along field margins. UC IPM says young green plants are preferred, especially lettuce, beans, corn, carrots, onions and some annual flowers. UC IPM says squash and tomatoes are among the least favoured, and Colorado State adds peas (tomato leaves, not fruit, it notes).
- Large, ragged sections chewed out of leaves
- Young plants eaten down, sometimes devoured entirely
- Flowers and annual bedding chewed
- Damage often worst along the edge next to grass, weeds or uncultivated ground
- Grasshoppers jumping or flying ahead of you as you walk through
- In major outbreaks, almost any green plant eaten and plantings stripped
Lifecycle & degree days
Most pest grasshoppers usually have one generation a year and spend the winter as eggs in the soil. Females lay egg pods in late summer and autumn in undisturbed ground, and prefer relatively dry soil not disturbed by tillage or irrigation (Colorado State). The eggs hatch as the soil warms in mid to late spring. In Colorado the young hoppers are in their hatching sites in May at lower elevations and early June higher up (Colorado State). Weather decides how many survive. Cold, wet weather kills newly hatched nymphs, and a very dry winter and spring can starve them of the tender growth they need.
- Eggs per pod
- 20 to 100+ (UC IPM); 20–130 (Kentucky)
- Where laid
- Top 2 in of undisturbed soil, late summer–autumn
- Hatch
- Mid to late spring as soil warms; young nymphs May–early June in Colorado
- Nymph
- 5–6 molts; about 40–60 days (red-legged, Kentucky)
- Adult life
- 2–3 months
- Generations / yr
- Usually one; most overwinter as eggs
Host crops
UC IPM and Colorado State agree on the favourites: lettuce, beans, sweet corn, carrots and onions, plus some annual flowers (UC IPM). Colorado State says squash, peas and tomato leaves (not the fruit) tend to be left alone.
Monitoring & action thresholds
No garden threshold was found in extension literature. The only numbers are for rangeland and on the biological bait labels. Kentucky Extension says the USDA-APHIS rangeland programme treats 8 adults, or the equivalent in nymphs, per square yard as an economic infestation. The now-cancelled Nolo Bait label, including its home-and-garden directions, said to use it at 8 or more grasshoppers per square yard. The Semaspore label calls 8 per square yard important and above 25 a serious infestation.
Start looking in late spring, when the nymphs hatch, rather than in summer when the damage shows. Walk the grassy and weedy margins around the garden and note how many small hoppers jump ahead of you. Colorado State says control works best on the young stages at the sites where eggs were laid, and that the biological bait cannot be used effectively once the adults have migrated. Keep checking the garden edge from early summer until frost. Colorado State adds that numbers in late summer and early autumn are a good guide to problems the following year.
Biological control
Grasshoppers have many natural enemies, and together they keep numbers low in most years. UC IPM lists birds, blister beetles, robber flies and fungal and bacterial diseases. Kentucky Extension adds the red locust mite on the eggs, tachinid flies, scelionid wasps, nematodes, ground beetles, toads and snakes. Colorado State names horned larks and kestrels among the birds, and the fungus Entomophaga grylli (it uses the older name Entomophthora grylli). The larvae of many blister beetles develop on grasshopper egg pods. You cannot buy most of these. UC IPM calls chickens and guinea hens excellent predators, though they can also damage some garden plants. The one product is the microsporidian bait Nosema locustae, and the evidence for it in gardens is weak. It infects only young nymphs of certain species, it is slow, and UC IPM says it is not likely to be effective in California home gardens. See the Nosema locustae page.
Cultural controls
In a garden, the practical answer is physical: keep grasshoppers off the plants that matter, and remove them by hand. UC IPM and Colorado State are the sources for the steps below.
- Cover the plants you most want to protect with floating row covers, or with metal window screening where numbers are high. UC IPM warns that hungry grasshoppers can chew through cloth and plastic
- Keep chickens or guinea hens if you can; UC IPM calls poultry excellent predators of grasshoppers, but warns they can also damage some garden plants
- Hand-pick where numbers are small; UC IPM lists it among the physical controls
- Keep an attractive green border of tall grass or lush plants around the garden, which UC IPM says can trap grasshoppers and divert them from vegetables. Don't mow it or let it dry out, or you send them straight in
- Watch the grassy and weedy margins in late spring, where the nymphs hatch; young grasshoppers are the only stage that biological bait can affect
- Where grasshoppers are a regular problem, lean on crops they tend to avoid: Colorado State names squash, peas and tomatoes. In major outbreaks, UC IPM says they will eat almost any green plant
Chemical, last resort
Rating: the effect on this pest's natural enemies if a spray hits them or they feed on treated plants. REI is the re-entry interval on farm and greenhouse labels; home labels usually give none, so follow the label.
Sources
UC IPM Pest Notes: Grasshoppers, UC ANR Pub. 74103 (Flint, updated 06/2013)
Colorado State Univ. Extension, Grasshopper Control in Gardens and Small Acreages (Cranshaw & Hammon)
Univ. of Kentucky ENTFACT-116, Three Common Kentucky Grasshoppers and Their Natural Enemies (rev. 2026)
US EPA, Nolo Bait label, Reg. No. 46149-2 (accepted 28 April 2023)
US EPA, Semaspore Bait label, Reg. No. 54735-5, now 95566-1 (accepted 8 April 2008)
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
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