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How to Keep Grasshoppers Off Plants Without Blanket Spraying

Row cover, a trap crop and Nosema locustae handle grasshoppers. Why sprays fail against adults and what timing actually matters.

By Salma 2 min read Save to Pinterest — opens Pinterest in a new tab
A green katydid resting on a broad leaf
Photo: Mylene2401, Pixabay Content License, via Pixabay
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Grasshoppers fly in from surrounding grassland, so nothing you put on a plant stops them for long. Exclusion works; timing works; spraying the vegetables in August does not.

What works, in order

measureeffectivenesswhen
Floating row cover / insect nettingHighWhenever they are active
Treating nymphs in marginsHighLate spring, while flightless
Nolo Bait (P. locustae)Moderate, slowLate spring on nymphs
Trap crop at the garden edgeModerateThrough the season
Kaolin clay on foliageLow–moderateReapply after rain
Encouraging birdsModerate, long termYear round
Contact spray on adultsLow—

Row cover done properly

  • Lightweight insect netting over hoops, not laid on the plants
  • Pinned or buried at every edge — grasshoppers walk in under a loose edge
  • Lift for pollination on fruiting crops, or hand-pollinate
  • Check inside weekly; one grasshopper sealed in does a lot of damage
  • Repair tears immediately

The timing that matters

  1. Autumn: mow and clear grassy margins where eggs are laid — this reduces next year’s hatch
  2. Late spring: nymphs hatch, small and flightless, concentrated at the field edge. This is the window. Nolo Bait or a targeted treatment here is worth ten times the same effort later
  3. Summer: adults arrive. Exclusion only
  4. Late summer: eggs laid in bare and grassy soil. Cultivating those areas exposes them

Blanket spraying is a net loss

Grasshoppers are eaten in huge numbers by birds, spiders, robber flies, toads, mantids and blister beetle larvae that eat the eggs themselves. A broad-spectrum spray removes those and does not stop the next wave flying in.

Encouraging the predators

  • Bird perches and cover near the garden, plus water
  • Chickens or guinea fowl if you keep poultry — guineas are relentless
  • Leave some rough grass away from the beds for toads and spiders
  • Avoid broad-spectrum insecticide anywhere near the garden

Common questions

What is the most effective way to stop grasshoppers eating plants?

Floating row cover over the crops you care about, pinned down at every edge. Grasshoppers are strong fliers and walk in from surrounding grassland, so nothing applied to a plant deters a hungry adult for long — physically excluding them is the only measure that reliably works through an outbreak. Light insect netting over hoops lets light and water through, needs no reapplication and protects the whole plant rather than the leaves you managed to spray.

Does spraying work on grasshoppers?

Poorly on adults, better on young nymphs. Adult grasshoppers are large, mobile and tough, so contact insecticides kill the ones they hit and the next wave flies in from the field next door. Treatment makes far more sense in late spring when nymphs are small, flightless and concentrated in the grassy margins where eggs hatched — treating the breeding ground early beats spraying the vegetables in August. Blanket spraying also kills bees, hoverflies and the predators eating the grasshoppers for you.

What is Nolo Bait and does it work?

It is bran bait carrying Paranosema locustae, a protozoan that infects grasshoppers, slows their feeding and eventually kills them, and it does work — slowly and best on nymphs. Expect weeks rather than days for effect and partial rather than total control, with its main value in reducing the next generation because infected insects pass it on. It is specific to grasshoppers and crickets, so it is safe around pollinators, pets and people, which is why it remains the main biological option.

Why do I suddenly have so many grasshoppers?

Weather, over several years. Grasshopper numbers build through warm dry summers, which favour egg survival and nymph development, and crash in cool wet springs when fungal disease takes the young. Outbreaks therefore follow a run of dry years rather than anything you did, and gardens next to unmown grassland, pasture or vacant lots take the worst of it because that is where the eggs were laid.

What eats grasshoppers?

A long list, which is the argument against blanket spraying. Birds take enormous numbers — blackbirds, meadowlarks and kestrels particularly — along with chickens and guinea fowl if you keep them, plus spiders, robber flies, blister beetle larvae which eat the eggs, praying mantids, toads, snakes and small mammals. Keeping bird cover, water and perches near the garden is a genuine long-term control measure.

Can I protect plants without covering them?

Partly, with a trap crop and timing. A strip of tall grass, oats or a few sacrificial plants at the garden edge concentrates arriving grasshoppers where you can treat or mow them rather than letting them reach the beds. Beyond that, mowing and removing the grassy margins where eggs are laid in autumn reduces next year's hatch, and kaolin clay sprayed on foliage makes leaves less palatable. None of it matches row cover during a serious outbreak.

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