Grasshoppers
Also known as Javanese grasshopper, Valanga nigricornis
In short
Grasshoppers are large chewing insects that can bite big pieces out of leaves or eat young plants entirely. Damage is patchy from year to year; outbreaks follow weather that favours their eggs and young.
How it looks
Medium to large insects with short antennae and greatly enlarged hind thighs for jumping. Nymphs look like small adults without full wings. In Southeast Asia, including Malaysia, the Javanese grasshopper (Valanga nigricornis) is common: adults are up to about 7.5 cm long, females larger than males, yellowish-brown, yellow or green with bluish-black markings and rose-red hind wings that show in flight; nymphs are pale green with dark markings.
Signs
Large, irregular pieces bitten out of leaf edges, sometimes whole young plants eaten; the insects themselves are usually easy to see and jump away when approached.
Life cycle
Females lay pods of about 20 to over 100 eggs in the top few centimetres of soil. Nymphs hatch and moult five or six times before becoming adults, which live two to three months. In temperate climates there is usually one generation a year.
What favours it
Warm, moist seasons that produce abundant food for nymphs; migration into gardens when surrounding vegetation dries out. For V. nigricornis, heavy rain kills many eggs and nymphs.
Prevention
- Protect small or valuable plants with covers; metal window screening holds up better than cloth or plastic.
- Leave a strip of tall grass at the garden edge as a trap crop to hold grasshoppers away from beds.
Treatment
Start with the first step and move down only if the problem persists.
- Hand-pick when numbers are low.
- Keep netting or screening over young plants until the grasshoppers move on.
- Chemical control works poorly once grasshoppers have invaded because sprays need frequent reapplication; if used, choose baits or products labelled for grasshoppers — follow the product label.
Pros and cons
Cons
- Can remove a lot of leaf area quickly on young plants.
Look-alikes
- Caterpillars
- Similar chewed holes, but caterpillars leave frass and stay on the plant rather than jumping away.
- Praying mantises
- Slender predators with grasping front legs held up; they do not chew plants.
Affected plants
Young, tender plants, especially lettuce, beans, corn, carrots, onions and some annual flowers; in Southeast Asia V. nigricornis is a serious pest of oil palm and rubber plantations.
Related
Sources
Written in our own words from these sources. Check a product label before using any treatment.