You wake up happy, grab a steaming cup of optimism and hope and head out to the garden. Sun is shining, birds are chirping but all is not right with the world today. You are confronted with sickly, yellowing, wilting plants begging for your help. What happened? Was it watering? Soil issues? A bug infestation? Or some other evil culprit threatening the health of your otherwise lovely garden?
Plant diseases and disorders come in all shapes and sizes. Some are a nuisance and some can be devastating. Some are seasonal and live in the soil while others can be genetic or introduced from pests or pollinators. Having some way to assess and identify the problem is your best bet to fighting it early and possibly saving your plants. One of our favorite resources for garden related information is the Rodale Institute and their publication (and website) Rodale’s Organic Life. They offer a great list and description of plant disorders including Blight, Cancers, Rusts and Rot.
The University of Minnesota’s Extension office has a great troubleshooting website that helps you identify your problem by answering a set of questions about what you’re experiencing to narrow down and identify the issue. It’s a great system for chasing down a problem you have no prior experience with. Simply choose what type of plant is effected, what variety then what part of the plant and the website runs you through a set of images to help identify the problem then offers advice for treating it.
Quick Reference Chart
|Problem||Possible Cause||Possible Cures and Controls|
|Seedlings do not emerge after sowing.||Not enough time has passed for germination.|
Temperatures are too cold.
Soil is too dry.
Soil is too wet; seeds rotted.
Birds or insects ate seeds.
Seed was too old, no longer viable.
Wait. Plant at proper time. Replant if necessary. Place a cloche or plastic sheeting over bed to warm soil before sowing.
Replant. Protect beds with horticultural fleece or place bird netting over beds.
Replant with fresh seed.
|Seedlings wilt and fall over. Young plants die.||Dry soil.|
Damping off (fungal disease).
Rotting roots or stems.
|Keep soil evenly moist. Bottom water seedlings growing indoors.
Avoid overwatering. Sow seed in sterile seed-starting mix. Treat soil with fungicide.
Avoid overwatering; add aged compost to soil
Follow fertilizer directions. Mix fertilizer thoroughly with soil.
Check for grubs curled in soil at base of plants. Keep garden clean of debris and plant residue. Keep garden weed-free. Use cardboard collars around seedlings.
Use floating row covers to exclude flies and moths from laying eggs in soil.
Use current season seed.
|Plants wilt.||Lack of moisture in soil.|
Too much water; poor drainage; waterlogged soil.
Root rot (fungal disease).
Vascular wilt (fungal disease often affecting tomato, potato, eggplant, pepper).
Root knot nematodes.
|Water deeply, thoroughly. Water when soil is dry to a depth of 3 or more inches.
Stop watering; improve drainage.
Grow disease-resistant varieties. Keep garden weed free and clean.
Do not overwater. Rotate crops.
Grow resistant varieties. Rotate crops. Solarize soil before planting.
Plant resistant varieties. Rotate crops. Solarize soil before planting.
|Plants are weak and spindly.||Not enough light; too much shade.|
Too much water.
Plants are crowded, spaced too close to each other.
Too much nitrogen.
|Locate garden where there is at least 6 to 8 hours of sunlight each day. Remove cause of shade or move plants.
Stop watering. Improve drainage.
Thin to spacing recommended.
Avoid excess fertilizing.
|Plants grow slowly; leaves are light green||Insufficient light; garden shaded.|
Cool weather; temperatures too low.
Improve soil pH.
Too much water.
|Thin plants to recommended distance. Plant where garden receives 6 to 8 hours of sunlight each day.
Protect plants with hot caps, cloches, and floating row covers.
Test soil pH. If alkaline, add soil sulfur, aluminum sufate, aged compost, peat moss.
Do not overwater. Improve drainage by adding aged compost and organic. amendments to soil. Grow crops in raised beds.
|Plant growth is stunted. Leaves are pale yellow and sickly looking.||Too much water. Poor drainage.|
Soil nutrient deficiency.
Compacted soil and not draining.
Acid soil; pH is low.
Insects or diseases.
Yellow or wilt disease, especially if yellowing attacks one side of the plant first.
|Reduce watering. Improve drainage by adding organic matter to planting beds.
Apply an even “complete” fertilizer; follow application instructions. Add aged compost to planting bed. Add aged-manure to beds in fall. Test soil for nutrient deficiency. Add trace elements.
Add 5 to 6 inches of aged compost or organic matter to soil. Turn soil to a depth of 10 to 12 inches. Improve drainage.
Test soil pH; add lime if necessary.
Identify insect of disease damage and follow recommendations form your extension service. See Problem Solver charts.
Remove affected plants; plant disease-resistant varieties.
|Leaves yellow but do not wilt.||Nutrient or mineral deficiency.|
Insufficient light; too much shade.
|Test soil for deficiencies. Add complete fertilizer. Add aged-compost to beds at least twice a year.
Thin plants to recommended distance to reduce shading. Move garden to sunnier location.
|Leaves mottle yellow and green, mosaic pattern. Leave pucker leaves; stunted plants.||Virus disease.||Remove and destroy infected plants. Remove plant debris. Practice insect, weed control. Plant disease resistant varieties.|
|Leaves and stems are spotted; darkened spots on stems and leaves. Seedlings turn brown and die.||Fertilizer or chemical burn; fertilizer placed directly on plant tissue or too much fertilizer added to soil.|
|Follow fertilizer instructions. Keep fertilizer off plant unless recommended. Apply at recommended rate. Mix fertilizers in soil to a depth of 3 inches or apply in bands to side of crop. Leach fertilizers from soil with water.
Identify disease and treat. Remove diseased plants. Grow disease-resistant varieties.
|Brown spots on leaves.||Fertilizer or chemical burn. Fertilizer placed directly on plant. Chemical placed on plant or drifted on wind to plant.||Follow fertilizer or chemical application instructions. Do not use fertilizers or chemical unless recommended for use on the plant. Apply fertilizer and chemicals at recommended rate.|
|Leaf margins look scorched, turn brown and shrivel.||Dry soil.|
Cold injury; low temperatures.
|Water deeply, thoroughly.
Salts applied to walkways and roads in winter may splash into garden; keep salty water off foliage. Flush soil with good water. Test soil for soluble salt level.
Avoid over application of fertilizers. Flush fertilizers from soil with water. Test soil for soluble salt level.
Test soil for deficiency. Apply fertilizer rich in potassium fertilizer; add wood ash or green sand at rate of 2 to 4 pounds per 100 square feet; add aged-compost, or aged-manure.
Protect plants with floating row covers, hot caps, or cloches. Plant at recommended times
|Leaves curled, puckered, or distorted.||Wilt.|
|Remove and destroy affected plants. Rotate crops. Grow disease-resistant varieties. Be aware of diseases that attack this plant.
Control aphids which spread viruses. Remove and destroy diseased plants. Be aware of diseases that attack this plant. Plant resistant varieties.
Keep soil evenly moist; avoid over-watering. Mulch to conserve soil moisture in hot weather.
Hand destroy. Spray away with water. Use insecticidal soap.
Apply herbicides when there is no wind. Follow herbicide directions; do not apply herbicides in middle of day. Control weeds by hand.
|Young leaves curl down, edges roll. Leaf surface become distorted and veins turn light color.||Weed killer damage.||Avoid using herbicides in garden. Hand weed.|
|Leaves stippled with tiny white spots.||Spider mites.|
Air pollution (ozone).
|Spray with insecticidal soap or treat with registered miticide.
Wash foliage with water; allow to dry before night.
|Powdery white coating on upper surface of leaves, stems, and flowers.||Powdery mildew (fungal disease); occurs when leaves are dry but weather is humid.||Plant resistant plants. Space plants widely to ensure good air circulation. Plant in full sun.|
|Leaves have holes; seedling and fruits chewed.||Insects, slugs, birds, rodents, rabbits.|
Heavy winds or hail.
|Identify pest; exclude with floating row covers, bird block or fencing. Use slug bait.
Protect plants from prevailing winds with hedges or cloth barriers. Protect crops from severe weather with row covers.
|Leaves shredded or stripped from plant.||Rodents, deer, slugs, hail damage.||Protect crops with fence, netting, for floating row covers. Use slug bait.|
|Blossom ends of tomatoes and peppers rot.||Dry weather following a wet spell. Uneven irrigation.|
Insufficient calcium in the soil.
Compacted soil; water and nutrient uptake impeded.
Too-deep cultivation; root injured disrupting water uptake
|Mulch to even out soil moisture. Water evenly.
Cultivate. Add aged-compost and organic matter to beds.
Avoid cultivating too deeply.
|No fruit.||Weather too cold; temperatures low.|
Weather too hot.
Too much nitrogen.
Plants not mature enough.
|Plant at proper time.
Plant so that crop comes to harvest before or after hot weather.
Follow feeding directions for variety. Avoid nitrogen-rich fertilizers. Feed soil with aged compost.
Pollinate with brush, or by shaking plant so that pollen will fall to female flowers (depending on kind). Attract pollinators to garden. Do not kill pollinating insects.
|Poor fruit yield; small fruit; poor flavor.||Uneven soil moisture.|
Poor soil fertility.
|Mulch to retain soil moisture. Water during dry periods. Make sure watering is even and deep.
Add aged compost or aged manure to planting beds.
Plant at right time of year.