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Common Vegetable Garden Problems: Cures and Controls

Tomato Leaf Curl web

Sometimes there will be problems in the vegetable garden. There is always a cause and there is often a cure or control.

Pest problems are often easy to spot: leaves or fruit look chewed or puckered from sucking pests. Diseases can be fungal, bacterial, or viral; often symptoms may look the same–brown or yellow spots on stems, leaves, or fruits. Environmental problems often appear after inclement weather.

Be patient and take a systematic approach to diagnose problems. Some problems will be easy and some will be difficult. Don’t be discouraged. Look also at these two articles for a photo gallery of pests and diseases: Vegetable Pest Problem Solver and Vegetable Disease Problem Solver.

Here is a guide to common problems with suggestions for possible causes and possible cures and controls.

Problem: Seedlings do not emerge after sowing

  • Cause: Not enough time has passed for germination. Cure: Wait.
  • Cause: Temperatures are too cold. Cure: Plant at the proper time. Replant if necessary. Place a cloche or plastic sheeting over the bed to warm the soil before sowing.
  • Cause: Soil is too dry. Cure: Water.
  • Cause: Soil is too wet; seeds rotted. Cure: Replant.
  • Cause: Birds or insects ate seeds. Cure: Replant. Protect beds with horticultural fleece or place bird netting over beds.
  • Cause: Seed was too old, no longer viable. Cure: Replant with fresh seed.

Problem:  Seedlings wilt and fall over. Young plants die.

  • Cause: Dry soil. Cure: Keep soil evenly moist. Bottom water seedlings growing indoors.
  • Cause: Damping-off (fungal disease). Cure: Avoid overwatering. Sow seed in a sterile seed-starting mix. Treat soil with fungicide.
  • Cause: Rotting roots or stems. Cure: Avoid overwatering. Sow seed in a sterile seed-starting mix. Treat soil with fungicide.
  • Cause: Fertilizer burn. Cure: Follow label instructions. Feed plants with aged compost.
  • Cause: Cutworms. Cure: Check for grubs curled in the soil at the base of plants. Keep the garden clean of debris and plant residue. Keep garden weed-free. Use cardboard collars around seedlings.
  • Cause: Root maggots. Cure: Use floating row covers to exclude flies and moths from laying eggs in the soil.
  • Cause: Old seed. Use the current season seed.

Problem: Plants wilt

  • Cause: Lack of moisture in the soil. Cure: Water deeply, thoroughly. Water when soil is dry to a depth of 3 or more inches.
  • Cause: Too much water; poor drainage; waterlogged soil. Cure: Stop watering; improve drainage.
  • Cause: Disease. Cure: Grow disease-resistant varieties. Keep the garden free of weeds and clean.
  • Cause: Root rot (fungal disease). Do not overwater.
  • Cause: Vascular wilt (fungal disease often affecting tomato, potato, eggplant, pepper). Cure: Grow resistant varieties.
  • Cause: Root-knot nematodes. Cure: Grow resistant varieties. Solarize soil before planting.

Problem: Plants are weak and spindly

  • Cause: Note enough light; too much shade. Cure: Locate the garden where there is at least 6 to 8 hours of sunlight each day. Remove the cause of shade or move plants.
  • Cause: Cool weather; temperatures too low. Cure: Protect plants with hot caps, cloches, or floating row covers.
  • Cause: Soil pH is wrong. Cure: Test soil pH. If alkaline, add soil sulfur, aluminum sulfate, aged compost, or peat moss.
  • Cause: Too much water. Cure: Do not overwater. Improve drainage by adding aged compost and organic. amendments to the soil. Grow crops in raised beds.

Problem:  Plants grow slowly; leaves are light green

  • Cause: Too much water. Poor drainage. Cure: Reduce watering. Improve drainage by adding organic matter to planting beds.
  • Cause: Soil nutrient deficiency. Cure: Apply an even “complete” fertilizer; follow application instructions. Add aged compost to the planting bed. Add aged-manure to beds in fall. Test soil for nutrient deficiency. Add trace elements.
  • Cause: Compacted soil not draining. Cure: Add 5 to 6 inches of aged compost or organic matter to the soil. Turn the soil to a depth of 10 to 12 inches. Improve drainage.
  • Cause: Acid soil; pH is low. Cure: Test soil pH; add lime if necessary.
  • Cause: Insects or diseases. Cure: Identify insect or disease damage and follow recommendations from your extension service.
  • Cause: Yellow or wilt disease, especially if yellowing attacks one side of the plant first. Cure: Remove affected plants; plant disease-resistant varieties.

Problem: Plant growth is stunted. Leaves are pale yellow and sickly looking.

  • Cause: Too much water. Poor drainage. Cure: Reduce watering, Improve drainage by adding organic matter to the planting bed.
  • Cause: Soil nutrient deficiency Cure: Apply a complete fertilizer; follow application instructions.
  • Cause: Compacted soil. Add 5 to 6 inches of aged compost or organic matter to the soil. Turn the soil to a depth of 10 to 12 inches. Improve drainage.
  • Cause: Acid soil; pH is low. Cure: Test soil pH; add lime if necessary.
  • Cause: Insects or diseases. Cure: Identify insect or disease damage and follow recommendations from the extension service.
  • Cause: Yellow or wilt disease, especially if yellowing attacks one side of the plant first. Cure: Remove affected plants; plant disease-resistant varieties.

Problem: Leaves yellow but do not wilt

  • Cause: Nutrient or mineral deficiency. Cure: Test soil for mineral deficiencies. Add complete fertilizer. Add aged compost to beds at least twice a year.
  • Cause: Insufficient light; too much shade. Cure: Thin plants to recommended distance to reduce shading. Move the garden to a sunnier location.

Problem: Leaves mottled yellow and green, mosaic pattern. Leave pucker leaves. Plant is stunted.

  • Cause: Virus disease. Cure:  Remove and destroy infected plants. Remove plant debris. Practice insect, and weed control. Plant disease-resistant varieties.

Problem: Leaves and stems are spotted; darkened spots on stems and leaves. Seedlings turn brown and die.

  • Cause: Fertilizer or chemical burn; fertilizer placed directly on plant tissue or too much fertilizer added to the soil. Cure: Follow fertilizer instructions. Keep fertilizer off the plant unless recommended. Apply at the recommended rate. Mix fertilizers in the soil to a depth of 3 inches or apply in bands to the side of the crop. Leach fertilizers from the soil with water.
  • Cause: Disease. Cure: Identify disease and treat it. Remove diseased plants. Grow disease-resistant varieties.

Problem: Brown spots on leaves.

  • Cause: Fertilizer or chemical burn. Fertilizer was placed directly on the plant. Chemical placed on plant or drifted on the wind to plant. Cure: Follow fertilizer or chemical application instructions. Do not use fertilizers or chemicals unless recommended for use on the plant. Apply fertilizer and chemicals at the recommended rate.

Problem: Leaf margins look scorched, turn brown, and shrivel.

  • Cause: Dry soil. Cure: Water deeply, thoroughly.
  • Cause: Salt damage. Cure: Salts applied to walkways and roads in winter may splash into the garden; keep salty water off the foliage. Flush soil with good water. Test soil for soluble salt level.
  • Cause: Fertilizer burn. Cure: Avoid over-application of fertilizers. Flush fertilizers from the soil with water. Test soil for soluble salt level.
  • Cause: Potassium deficiency. Cure: Test soil for deficiency. Apply a fertilizer rich in potassium fertilizer; add wood ash or green sand at a rate of 2 to 4 pounds per 100 square feet; add aged compost or aged manure.
  • Cause: Cold injury; low temperatures. Cure: Protect plants with floating row covers, hot caps, or cloches. Plant at recommended times.

Problem: Leaves curled, puckered, or distorted.

  • Cause: Viral disease. Cure: Control aphids that spread viruses. Remove and destroy diseased plants. Be aware of diseases that attack this plant. Plant resistant varieties.Control aphids that spread viruses. Remove and destroy diseased plants. Be aware of diseases that attack this plant. Plant resistant varieties.
  • Cause: Moisture imbalance. Cure: Keep soil evenly moist; avoid over-watering. Mulch to conserve soil moisture in hot weather.
  • Cause: Aphids. Cure: Hand destroy aphids. Spray away with water. Use insecticidal soap.
  • Cause: Herbicide injury. Cure: Apply herbicides when there is no wind. Follow herbicide directions; do not apply herbicides in the middle of the day. Control weeds by hand.

Problem: Young leaves curl down, edges roll. Leaf surface becomes distorted and veins turn light color.

  • Cause: Weed killer damage. Cure: Avoid using herbicides in the garden. Hand weed.

Problem: Leaves stippled with tiny white spots.

  • Cause: Spider mites. Cure: Spray with insecticidal soap or treat with a registered miticide.
  • Cause: Air pollution (ozone). Cure: Wash foliage with water; allow to dry before night.

Problem: Powdery white coating on the upper surface of leaves, stems, and flowers.

  • Cause: Powdery mildew (fungal disease); occurs when leaves are dry but the weather is humid. Cure: Plant resistant plants. Space plants widely to ensure good air circulation. Plant in full sun.

Problem: Leaves have holes; seedlings and fruits are chewed.

  • Cause: Insects, slugs, birds, rodents, rabbits. Cure: Identify pest; exclude with floating row covers, bird block, or fencing. Use slug bait.
  • Cause: Heavy winds or hail. Cure: Protect plants from prevailing winds with hedges or cloth barriers. Protect crops from severe weather with row covers.

Problem: Leaves shredded or stripped from plant.

  • Possible cause: Rodents, deer, slugs, hail damage. Cure: Protect crops with fence, netting, for floating row covers. Use slug bait.

Problem: Blossom ends of tomatoes and peppers rot.

  • Possible cause: Dry weather following a wet spell. Cure: Mulch to even out soil moisture.
  • Possible cause: Uneven irrigation. Cure: Water evenly.
  • Possible cause: Insufficient calcium in the soil. Cure: Add lime.
  • Possible cause: Compacted soil; water and nutrient uptake impeded. Cure: Cultivate. Add aged compost and organic matter to beds.
  • Possible cause: Too-deep cultivation; root injuries disrupting water uptake. Cure: Avoid cultivating too deeply.

Problem: No fruit.

  • Cause: Weather too cold; temperatures low. Cure: Plant at the proper time.
  • Cause: Weather too hot. Cure: Plant so that crop comes to harvest before or after hot weather.
  • Cause: Too much nitrogen. Cure: Follow feeding directions for variety. Avoid nitrogen-rich fertilizers. Feed soil with aged compost.
  • Cause: No pollination. Cure: Pollinate with a brush, or by shaking the plant so that pollen will fall to female flowers (depending on the kind). Attract pollinators to the garden. Do not kill pollinating insects.
  • Cause: Plants are not mature enough. Cure: Wait.

Problem: Poor fruit yield; small fruit; poor flavor.

  • Cause: Uneven soil moisture. Cure: Mulch to retain soil moisture. Water during dry periods. Make sure watering is even and deep.
  • Cause: Poor soil fertility. Cure: Add aged compost or aged manure to planting beds.
  • Cause: Improper temperature. Cure: Plant at the right time of year.

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. Harvesttotable.com has more than 10 million visitors each year.

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    • Roots that are crowded will not mature; so be sure to thin root crops. Too much nitrogen in the soil will result in green top growth and little root maturation. Feed root crops with low nitrogen, high phosphorus fertilizer.

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