Grasshoppers
Acrididae — chiefly Melanoplus spp.
also called Locusts
In a dry western summer they arrive from the surrounding grassland and chew everything down to stubs. Mesh is the only reliable defense once numbers are up.
How to know it
A stout-bodied insect 20–40 mm long with enormous hind legs, short antennae and leathery forewings folded over the back, in gray, brown or green. Nymphs are wingless miniatures. What separates a plague from a passing few is where they come from — the roadside and the pasture, not the garden.
What you'll see
- Leaves chewed from the margins inward in large irregular bites, and whole leaves gone by the next day.
- Stems and petioles gnawed through, leaving a plant standing but stripped.
- Grasshoppers rising in numbers ahead of your feet as you walk the garden edge.
- Damage heaviest on the boundary nearest rough grass or a fallow field, and lighter toward the house.
- Rasped, scarred fruit and chewed bark on young stems late in a bad year.
Where it comes from
Eggs are laid in pods in undisturbed dry soil — roadsides, pasture, fencelines — in late summer and hatch the following spring over several weeks. The nymphs feed and grow through five or six molts in the grassland, then fly into gardens as the grass dries off in midsummer. One generation a year.
Outbreaks follow dry, warm springs, which suit the eggs and starve the fungal diseases that usually check the nymphs. Two or three dry years in a row build the numbers that make a plague year. Gardens next to rangeland, hayfield or an untended lot take the worst.
Dealing with it
- Cover valued crops with mesh or floating row cover — at real numbers this is what works and nothing else does.
- Treat the hatching ground, not the garden: Nosema locustae bait spread on the rough grass in late spring reaches the young nymphs.
- Keep a barrier strip of tall grass at the boundary and mow it late, so they stop there first.
- Encourage the birds, and keep poultry where you can — hens work a boundary strip hard.
- Water the garden well through the worst of it; a turgid plant is chewed no less but recovers far better.
Keeping it out
- Cultivate any fallow ground in late summer to break up the egg pods before winter.
- Keep the immediate garden edge mown short, which gives no cover to the arriving nymphs.
- Plan a mesh cover for the vegetable beds in the second dry year, not the third.
- Grow tougher, less-favored plants at the garden edge and the tender crops in the middle.
- Leave hedgerow habitat for the birds and the robber flies that take a real toll on them.
What it goes for
Almost anything green, but lettuce, beans, sweetcorn, carrots, onions and young trees are the first to go.
Who hunts it for you
- Garden birdsPasseriformes Both things are true: birds strip your currants and a brood of blue tits takes several thousand caterpillars out of one fruit tree in a fortnight. Net what you must and welcome them everywhere else — a nest box near the apples is worth more than a spray. Grow to recruit it: Echinacea,Elderberry,English holly,Goldenrod,Rudbeckia,Sunflower
- Praying mantisMantidae A sit-and-wait ambusher that snatches caterpillars, beetles, and anything else that wanders close — friend and foe alike, so count it a mixed blessing. Tall, structured plantings give it perches and egg-case anchors. Grow to recruit it: Cosmos,Fennel,Sunflower
- Snakes & lizardsColubridae & Phrynosomatidae A garter snake works the beds for slugs and voles and a fence lizard clears grasshoppers off a sunny wall. Almost every snake a gardener meets is harmless and useful; give them a log pile, a warm flat stone and a bit of cover and they stay.
- Soldier beetleCantharidae Soft-winged beetles seen mating on flower heads in high summer; adults and larvae both take aphids and soft grubs. Open composite flowers are their landing pads and hunting grounds. Grow to recruit it: Echinacea,Rudbeckia,Sunflower,Yarrow,Zinnia
See also
The Cottage Garden Companion — the gardener's bestiary at cottagegardencompanion.com