10 Pests That Could Be Eating Your Zucchini Leaves

Zucchini make big, beautiful plants in the vegetable garden. The large palm-shaped leaves enable the plant to produce its bounty of fruits. Damaged foliage is usually the first sign of trouble and it helps to know the cause so you can take steps to protect and preserve your crop. T

his guide helps identify the insect pest feeding on the leaves and vines of your zucchini plants.

Squash Bug

Squash bugs, Anasa tristis, are the pest most damaging to zucchini leaves. Gray in color with faint yellow striping, they look a bit like stink bugs but bigger with a flatter appearance. Like stink bugs, they emit a bad smell when crushed.

Round, reddish eggs deposited on zucchini leaves are easily seen. Both nymphs and adults feed on leaves and stems leaving yellow spots that eventually turn brown.

Photosynthesis is disrupted and young plants can wilt and die. Adults hide under garden debris and overwinter in sheltered locations.

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Slugs

Slugs, Gastropoda, appear early in the growing season to feed on young vegetable plants including zucchini leaves.

Irregularly shaped holes in leaves, stems and fruit along with a silvery trail are signs of slug damage. Slugs are most active at night and in cool, damp weather. Seedlings and young plants are at greatest risk.

Squash Vine Borer

If your zucchini plants start wilting down overnight, it’s likely the work of the squash vine borer, Melittia cucurbitae. Adults are a species of clear-wing moth, easily identified by their black-spotted, orange abdomen.

Females lay eggs at the base of the plant where grayish-white grubs hatch to tunnel into vines and feed, disrupting the flow of water and nutrients, causing the vine to die. If you suspect squash vine borer, look for a buildup of grainy or powdery material at the base of the vine.

Snails

Common garden snails, Cornu aspersum, are late-season arrivals to many gardens, preferring to feed during warmer, drier weather. Closely related to slugs, snails carry a shell that protects them from hot summer conditions.

They, too, leave behind a slimy trail that may appear silvery or clear. Irregular holes with smooth edges in leaves are a sign snails have been at work in your zucchini patch.

Cucumber Beetles

Both striped, Acalymma vittata, and spotted cucumber beetles, Diabrotica undecimpunctata howardi, carry diseases including bacterial and fusarium wilts, and squash mosaic virus. They also kill young zucchini plants by girdling stems and chewing ragged holes in leaves. Cucumber beetles feed on all plant parts including flowers which disrupts fruit production, and sometimes damage maturing fruit as well.

Adults are about an inch long with beaded antennae and distinct markings. The striped beetle is pale yellow with a black head and three black stripes. Spotted cucumber beetle is bright yellow-green with a black head and 12 black spots.

Leafminers

Adult leafminers are a type of fly that lays small, white eggs into leaf tissue at the base and along the edges. Of several different species, the larvae of the vegetable leafminer, (Liriomyza sativae), is the pest leaving white meandering trails and splotches on zucchini leaves.

Larvae are tiny yellow maggots difficult to see so their zig-zag trails are the best way to identify a problem. They feed on plant material between the upper and lower surfaces of leaves, interrupting the flow of water and nutrients and creating openings for bacteria and other diseases.

While a more serious pest of leafy greens and root vegetables, an infestation can reduce the zucchini harvest.

Aphids

Aphids, Aphidoidea, are tiny ( 1/16 inch) soft-bodied, pear-shaped pests found on almost every plant in the garden. They can be different colors including green, black, red, brown, yellow, and gray, and some species are winged. Immature aphids look like adults only smaller.

As they mature they shed exoskeletons leaving a white shell easily seen against green foliage. Aphids, alone, rarely kill a mature plant but some types carry disease and all aphids suck juices from leaves and stems leaving a sticky substance called honeydew.

Aphids cause mottling, yellowing, and curling leaves and can stunt plant growth.

Flea Beetles

Flea beetles are small (1/16- to 1/8-inch) pests of vegetable plants. Most species feed on specific plants but the pale, striped flea beetle, Systena blanda, is a generalist and can cause damage to zucchini leaves.

Adults are active in early spring chewing irregular holes and creating shallow pits in leaves. Pitting is unique to flea beetles. They congregate in large groups on a leaf and cause wilting and stunting. Seedlings are particularly vulnerable.

Thrips

Many species of thrips exist and not all are pests, but stippled, curling leaves that start to yellow or develop gray or white patches may be the result of the common onion thrip, Thrips tabaci.

These slender, pale pests are too small to spot without magnification but suck the sap from foliage and leave behind a trail of small black frass, or excrement.

Spider Mites

Spider mites are another tiny insect pest in bright colors of red, yellow, and green that make them easier to spot. They feed on the undersides of leaves causing yellow to bronze speckling.

Plants lose vigor, become stunted, and foliage may turn brown and drop prematurely. Grayish-white webbing on the undersides of leaves is a sign of severe spider mite activity.