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Symptoms and Pests
On this page, find symptoms of various plant pests, identification of the pest likely to be causing the condition, and options for treating or controlling the pest and returning your vegetable plants to good health.
Using the Vegetable Pest Identification Table
Scan this list of common plant pests. For each pest, you’ll find a description of symptoms or conditions that match those you find in on your plants in your garden, and control measures or cures.
If the cure requires application of sprays or other treatments, follow the control’s package directions and label instructions, and review the step-by-step demonstration of how to apply dry and liquid sprays to vegetable plants [See: Applying Garden Chemicals].
Remember to choose first the least-toxic control measure, and limit treatment to areas of active pest infestations.
To control difficult-to-treat, resistant, or recurring infestations of treated pests, follow the principles, practices, and methods of Integrated Pest Management [See: Integrated Pest Management].
Vegetable Plant Pest Identification Table
Symptom: Leaves curled and twisted, often with a black, sooty appearance. Deformed or stunted blooms on new growth.
Cause: Aphids. Look for soft-bodied, round, black, gray, green, or yellow insects, 1/16–1/4 inch (1.5–6 mm) long. Found on many plants. Frequently found in combination with ants.
Cure: Wash off light infestations with a strong stream of water. If ineffective, dust with diatomaceous earth or spray with superior oil. Spray with botanical neem oil or pyrethrin as a last resort.
Symptom:Green parts of leaves are chewed, removed, or left in place stripped to veins. Later, leaves are dry and skeletonized.
Cause: Beetles, including Colorado potato beetles, Japanese beetles, and beetle larvae. Hard-shelled beetles are most active in the heat of the day.
Cure: Hand pick beetles after shaking plant in early morning while they are inactive. Apply milky spore (Bacillus popilliae) for Japanese beetle grubs, Bacillus thuringiensis(BT) for Colorado potato beetles. Spray with botanical neem oil or pyrethrin as a last resort.
Symptom: Foliage is eaten and stems are scored or eaten. Black or brown droppings, 1/20 in. (1.2 mm) wide are left on foliage. Moths and butterflies are seen resting on plants.
Cause: Various larvae and caterpillars, white cabbage moth, tomato hornworm, wormlike larvae, and loopers. Look at undersides of leaves and along stems for pests during midday.
Cure: Hand pick caterpillars from center leaves of plant. Release parasitic wasps and flies. Spray with Bacillus thuringiensis (BT). Apply horticultural oil in summer.
Symptom: White trails on or within leaves; papery yellow or brown blotches on foliage.
Cause: Leaf miners. Look for small, pale larvae and 1/6-in. (4.2-mm) tiny, green or black, flying insects active during the day.
Cure: Hand pick larvae. Remove infested leaves. Release lady beetles. Spray foliage with neem oil as a last resort.
Symptom: Stunted, discolored, spotted plants with deformed roots, sometimes bearing swollen galls; loss of vigor.
Cause: Soil nematodes, microscopic wormlike creatures that live in soil and feed on plant roots.
Cure: Release beneficial nematodes. Remove and destroy affected plants. Replant with unrelated species. Solarize bed for 3–4 weeks prior to planting by covering soil with clear plastic and allowing sunlight to raise soil temperature to 140°F (60°C) [See: Nematodes and Infested Soil].
Symptom: Leaves with brown or black spots. Roots and shoots may be deformed.
Cause: Plant bugs. Look for greenish yellow or tan insects 1/4 in. (6 mm) long.
Cure: Hand pick. Spray with insecticidal soap. If infestation is severe, spray affected areas with pyrethrin or rotenone as a last resort.
Symptom: Brown-, silver-, or white-speckled leaves; may be gummy or deformed. Blooms are deformed and fail to open.
Cause: Thrips. Shake foliage and blossoms over white paper and look for moving, winged specks. Thrive in hot, dry conditions.
Cure: Release lady beetles. Remove and destroy infested foliage. Wash foliage with water; spray pests with insecticidal soap.
Symptom: Yellow leaves and stunted, sticky plants. When foliage is shaken, a cloud of white insects may fly up.
Cause: Whiteflies. Shake foliage and look for 1/20-in. (1.2-mm) mothlike, flying insects. Inspect leaf undersides for scalelike, gray or yellow eggs.
Cure: Catch with sticky traps. Spray with soap solution. Spray infested foliage with insecticidal-soap. Spray foliage with horticultural oil or neem oil extract solution. Spray with pyrethrin as a last resort.
Symptom: Ripe and half-ripened fruit and berries bear numerous cuts and holes. Partially eaten produce covers the ground, accompanied by bird droppings.
Cause: Birds. Look for songbirds, crows, and other fruit-eating species that forage on or near the ground.
Cure: Mount silver-foil streamers or pinwheels over vegetables. Cover beds with floating row covers as fruit and berries begin to ripen [see Row Covers and Mulching]. Hang and move frequently owl and hawk silhouette decoys.
Symptom: Uprooted plants; foliage eaten to ground level; bulbs and roots eaten, leaving dying stalks and leaves.
Cause: Deer and rodents. Look for hoof and paw prints, burrows, mounds, and tunnels.
Cure: Plant resistant plants. Install fence barriers or cages when planting, including beneath-soil barriers [see Fences and Animal Pests]. Trap and remove rodents. Avoid bonemeal, fish emulsion use.
Symptom:Chewed leaves and blossoms; silvery mucus trails.
Cause: Slugs and snails. After dark, look for shelled and unshelled mollusks on foliage or soil.
Cure: Remove leaf litter, which is used as a hiding place. Hand pick after dark; use copper foil barriers around beds or containers; dust with diatomaceous earth; use beer-filled traps; use non-toxic baits containing iron phosphate; use bait gel.
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