These tiny, soft-bodied bugs attack in swarms. They’re about the size of a pencil tip and range in color from bright green to rusty brown. They feed on the undersides of leaves by sucking on the veins.
- Scars or white spots on the leaves
- Wilting or yellowing
- Tarry black residue on the leaves
- Ants— aphids produce a sweet residue that ants love
Treat for aphids by spraying your plants with insecticidal soap, a mild pesticide that’s less toxic to beneficial insects. Be sure to apply it to the underside of the leaves as it must come in contact with the aphids to be effective.
There are two varieties of cucumber beetle: striped and spotted. Both are bright yellowish orange with black markings. The larvae—orange grubs—and adults can chew leaves, flowers, and even fruits, and also spread several diseases.
- Holes in leaves and flowers
- Patchy yellow spots on leaves
- Damage to fruits
- Wilted leaves
Protect your zucchini by waiting until well after the last frost to plant; this allows overwintered larvae to hatch out and leave the area. Row cover protects growing plants. Remove it once plants bloom to allow pollinators access.
If you need to treat a severe infestation, neem oil is a good option that kills the insects in several stages, and also helps protect from diseases that might take advantage of weakened plants.
These grub-like insects are the larvae of the clearwing moth. The moths, which have black bodies, rusty markings, and transparent wings, lay eggs on the stems of zucchini plants. When the eggs hatch, the larvae burrow into the vines.
- Sudden leaf wilting
- Rust-colored eggs on the stems of plants
- Rotten stems
- Borer holes at the base of stems
Pesticides are often ineffective against established borers since they’re protected inside the vines. The only way to get rid of them is to remove and dispose of leaves as soon as they show symptoms.
If possible, prevention is the best defense against vine borers. Use yellow sticky traps to catch adult moths before they can lay eggs, and try discourage them from lingering near your zucchini with companion plants like nasturtium and marigold.