Squash Bugs
TreatablePest · spreads to other plants
Squash bugs feed by injecting saliva that kills leaf tissue, so a heavy population yellows and then kills leaves progressively. They hide at the base of the plant and under mulch, and they are notoriously hard to kill as adults — which makes egg removal the practical control.
What it looks like
Flat grey-brown shield-shaped bugs about half an inch long, clustered at the base of the plant and under leaves, with grey nymphs alongside them. Neat rows of bronze eggs are laid in the V between leaf veins. Leaves develop yellow speckling then brown and die.
How to confirm it
- Neat, regularly spaced bronze eggs in the angle between leaf veins. Nothing else lays like this.
- Flat grey-brown adults that scuttle for cover when you lift a leaf.
- Yellow speckling spreading to brown death of whole leaves.
- A distinct unpleasant smell when crushed.
What to do
- 1Scrape egg clusters off leaves with a fingernail or lift them with tape. This is the highest-value ten minutes you can spend.
- 2Lay a board flat near the plant overnight; adults shelter under it and can be collected in the morning.
- 3Hand-pick adults and nymphs into soapy water.
What it gets confused with
One observation settles each of these.
Cucumber beetles are yellow with black stripes or spots and move fast; squash bugs are flat, grey-brown and shield-shaped.
Preventing it next time
- Clear all squash debris in autumn — adults overwinter in it.
- Delay mulching, since mulch gives them daytime shelter.
- Row cover until flowering, then remove for pollination.
Plants affected
Check these two things first
- Push a finger into the soil, two knuckles deep. Wet soil plus a wilting plant means too much water, not too little — and it is the commonest reason a plant is dying. Dry soil plus crisp leaves means the opposite. The leaves look nearly identical either way, so the soil is what tells you.
- Turn a damaged leaf over. Half of all diagnoses live on the underside: fuzz means downy mildew, fine webbing means spider mites, clusters of insects mean aphids. Nothing on the top of a leaf is as informative.
Most garden problems are cosmetic and resolve without treatment. Reach for a spray last, not first.