Squash & Zucchini insects on the plant
There are 4 common causes, and they need completely different responses — so working out which one you have matters more than treating quickly.
2 of them can kill the plant. Rule those out first.
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.
The 4 causes, and how to tell them apart
1.Cucumber Beetles
Act nowPest
Small yellow-green beetles a quarter of an inch long with either three black stripes down the back or twelve black spots. They chew holes in leaves and flowers and drop off the plant when disturbed.
How to know it is this one
Yellow-green beetles with black stripes or spots, about a quarter inch.
2.Spider Mites
Act nowPest
Fine pale stippling across the leaf, as though it had been sprayed with a very fine dust of pinpricks. Leaves go bronze or grey, and fine webbing appears between leaves and along stems in bad infestations. The mites themselves are just visible as moving specks.
How to know it is this one
Fine even stippling rather than discrete spots or holes.
3.Aphids
TreatablePest
Clusters of small soft-bodied insects, usually green but also black, grey, pink or white, packed along new shoots and the undersides of young leaves. Leaves curl and pucker, and everything below becomes sticky with honeydew.
How to know it is this one
Dense clusters on new shoots and flower buds rather than scattered individuals.
4.Squash Bugs
TreatablePest
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 know it is this one
Neat, regularly spaced bronze eggs in the angle between leaf veins. Nothing else lays like this.
Still not sure?
The diagnostic key adds two more questions — which part is affected and where the trouble started — and those usually settle it.
Run the diagnostic key