Grasshoppers aren’t dangerous to people or pets, but they can be genuinely destructive to gardens, crops, and rangeland. Whether they’re “bad” depends entirely on context: in your vegetable garden, a swarm of grasshoppers is a real problem. In a prairie ecosystem, they’re essential. Here’s what you need to know about both sides.
Garden and Crop Damage
Most grasshopper species specialize in eating grasses or broadleaf plants and aren’t much of a concern. The trouble comes from a handful of pest species, particularly the differential and two-striped grasshoppers, which feed on a wide variety of plants and readily switch between food sources. These are the ones that show up in your garden and start chewing through roses, day lilies, irises, cannas, vegetables, and ornamental shrubs.
The damage can be substantial. In grasslands, grasshoppers consume up to 150% as much aboveground plant material as cattle do across the same area. In a home garden, even a moderate population can strip leaves, flowers, and developing fruit in a matter of days. They tend to feed from the outside edges of leaves inward, leaving ragged holes or completely skeletonized foliage.
When Grasshopper Numbers Actually Matter
Not every grasshopper you see warrants concern. Guidelines from the University of Nebraska help put density into perspective:
- 0 to 2 per square yard in a field: Not an economic problem. No treatment needed.
- 3 to 7 per square yard: A light infestation. Whether it matters depends on what you’re growing.
- 8 to 14 per square yard: Moderate. Control is probably worthwhile.
- 15 or more per square yard: Heavy infestation. Active management is needed.
On rangeland, control is rarely justified until numbers exceed 12 per square yard, and even then the decision depends on the value of the forage and the cost of treatment. In a home garden with prized vegetables or flowers, your personal threshold will be lower since even a few grasshoppers can do noticeable damage to individual plants.
The Locust Question
Locusts are grasshoppers. Specifically, they’re certain grasshopper species that undergo a dramatic behavioral transformation when crowded together. When rain produces a burst of vegetation, locust populations boom. As food dwindles, the insects get funneled into shrinking patches of green and are forced into contact with each other. This physical crowding triggers a rapid shift: solitary, harmless grasshoppers become highly mobile, group-seeking swarms.
Research from the University of Cambridge pinpointed the chemical mechanism behind this change. When grasshoppers are jostled by others (even just having their hind legs touched repeatedly in a lab), serotonin levels in their nervous system triple within two hours, flipping a behavioral switch. Blocking serotonin prevents the transformation entirely. Injecting serotonin triggers swarming behavior even when the insect is alone. This is why locust swarms seem to appear out of nowhere: the insects were already there, just behaving differently.
If you live in North America, you’re unlikely to encounter true swarming locusts. The Rocky Mountain locust went extinct in the early 1900s. But devastating locust swarms remain a serious threat in parts of Africa, the Middle East, and South Asia.
Why Grasshoppers Matter Ecologically
Outside of gardens and farms, grasshoppers play a surprisingly important role. They’re a major food source for birds like horned larks and kestrels, as well as robber flies, blister beetles, coyotes, and various parasitic insects. Removing grasshoppers from an ecosystem has ripple effects up the food chain.
Their contribution goes beyond being prey. By eating plants and excreting waste, grasshoppers convert plant tissue into forms that soil microbes can quickly break down and recycle. Their droppings create nutrient hotspots where decomposers thrive, speeding up the return of carbon and nitrogen to the soil. Their carcasses, which are numerous and break down fast, do the same. Preliminary research from the Smithsonian Conservation Biology Institute found that long-term reductions in grasshopper populations led to significant drops in soil carbon and nitrogen storage. In other words, grasslands need their grasshoppers.
Are They Harmful to People or Pets?
Grasshoppers aren’t poisonous, don’t sting, and rarely bite. A grasshopper can technically bite if it feels threatened, but the bite isn’t dangerous and doesn’t inject venom. In general, they pose no risk to people, dogs, cats, or homes. A pet that eats a grasshopper will almost certainly be fine, though eating large numbers could cause mild stomach upset simply from the volume of exoskeleton material.
Managing Grasshoppers in Your Garden
If grasshoppers are eating your plants, you have several options that don’t involve broad-spectrum pesticides. Physical barriers like floating row covers can protect vulnerable crops. Birds are natural allies, so encouraging kestrels, sparrows, and other insect-eating birds with perches and habitat helps keep populations in check.
For biological control, bait products containing Nosema locustae (sold as NOLO Bait or Semaspore) are approved for certified organic production and selectively target grasshoppers without harming other insects. There are important limitations, though: the bait only works on young grasshoppers, acts slowly, and doesn’t affect all species equally. It’s best used as part of a longer-term management strategy rather than a quick fix for an active adult infestation. The bait is also perishable and should be refrigerated before use, so check the expiration date before applying.
Natural diseases and parasites also help. A fungus called Entomophthora grylli kills grasshoppers and spreads through populations during wet weather. If you find stiff, dead grasshoppers clinging to the tops of grass stems or twigs, this fungus is already at work in your yard. Wet seasons naturally suppress grasshopper numbers through these biological agents, which is one reason outbreaks tend to be worst during hot, dry years.