Urban Farmer Plant Health
Plant Problem Diagnostic Guide
Start with what you see. Match symptoms to common garden pests, diseases, nutrient problems, and growing conditions—then learn what to do next.
Start your diagnosis
What is happening to your plant?
Select a symptom, choose a crop, or search for a pest or problem.
1. Choose the closest symptom
Likely matches
Common garden problems
Compare all identifying clues before choosing a response.
Dark, sunken tissue develops at the blossom end of young fruit.
- Usually affects tomatoes, peppers, squash, or melons
- Often follows uneven soil moisture
- The damaged area becomes leathery
What to do
Keep soil moisture even, mulch around plants, and avoid damaging roots. Remove badly affected fruit. Adding calcium only helps when a soil test shows a true deficiency.
White, flour-like growth spreads across the upper leaf surface.
- Common on squash and cucumbers
- Older leaves are often affected first
- Growth can spread during warm, humid weather
What to do
Remove heavily infected foliage, improve airflow, water at soil level, and avoid working among wet plants. Use a product labeled for the crop and disease when treatment is necessary.
A hidden larva tunnels inside the stem and causes sudden wilting.
- Sawdust-like frass near the stem base
- One runner may wilt before the rest
- Stem can appear split or hollow
What to do
Inspect the lower stem and remove the larva when practical, then mound moist soil over the damaged section to encourage rooting. Remove destroyed vines after harvest.
Older leaves become pale green or yellow and plant growth slows.
- Begins on older, lower foliage
- Yellowing is usually fairly uniform
- Plant may look thin or stunted
What to do
Confirm with a soil test when possible. Apply a crop-appropriate nitrogen source according to the label and avoid overfertilizing, which can cause weak growth and fewer flowers.
Small jumping beetles leave many pinhead-sized holes in leaves.
- Young seedlings are damaged most severely
- Beetles jump when disturbed
- Common on brassicas and eggplant
What to do
Protect seedlings with insect netting or row cover, control nearby weeds, and keep young plants growing vigorously. Use only products labeled for the crop and pest.
Clusters of soft-bodied insects feed on tender growth and curl leaves.
- Sticky honeydew may coat foliage
- Look under leaves and on new growth
- Ants may gather around colonies
What to do
Knock aphids off with a firm stream of water, encourage beneficial insects, and prune badly infested tips. Insecticidal soap must contact the insects directly.
Brown leaf spots develop concentric, target-like rings.
- Usually begins on lower tomato leaves
- Yellow tissue surrounds older spots
- Splashing water can spread spores
What to do
Remove infected lower leaves, mulch to reduce soil splash, water at the base, rotate crops, and provide generous spacing. Do not compost heavily infected debris.
Individual leaves or entire vines wilt despite adequate soil moisture.
- Common on cucumbers and melons
- Often associated with cucumber beetles
- Vines may collapse rapidly
What to do
Remove affected plants to slow spread and manage cucumber beetles early. Rotate cucurbit crops and clean up plant debris at the end of the season.
Green caterpillars chew irregular holes in brassica leaves.
- Dark green droppings collect on leaves
- Caterpillars hide near leaf veins
- White butterflies may visit plants
What to do
Handpick caterpillars, protect crops with insect netting, and inspect leaf undersides for eggs. Bt products can help when used according to label directions.
Tomato skins split after rapid fruit expansion.
- Often follows heavy rain or uneven watering
- Cracks may circle the stem or radiate outward
- Some varieties crack more readily
What to do
Maintain even moisture, mulch plants, harvest ripe fruit before heavy rain, and choose crack-resistant varieties when the issue occurs repeatedly.
Roots deprived of oxygen can cause yellowing, drooping, and slow growth.
- Soil stays wet for long periods
- Lower leaves may yellow first
- Roots can turn brown and soft
What to do
Let the upper soil begin drying before watering again, improve drainage, and water deeply but less often. Containers must have clear drainage holes.
Sudden intense sunlight bleaches leaves or exposed fruit.
- Damage appears white, tan, or papery
- Often follows transplanting or pruning
- Affected tissue faces the strongest sun
What to do
Harden seedlings off gradually, preserve enough foliage to shade fruit, and use temporary shade during abrupt heat or sun exposure.
Water-soaked lesions quickly turn brown and spread through foliage or fruit.
- Most serious on tomatoes and potatoes
- White growth may appear beneath leaves
- Cool, wet weather favors rapid spread
What to do
Remove and bag infected plants promptly, avoid overhead watering, and do not compost diseased tissue. Contact your local Extension office when late blight is suspected.
Plants yellow and wilt even though the soil contains adequate moisture.
- One side of a plant may decline first
- Lower leaves often yellow before wilting
- Stem tissue may look brown inside
What to do
Remove badly affected plants, rotate away from susceptible crops, sanitize tools, and avoid moving contaminated soil. Choose resistant cultivars for future plantings.
Leaves develop a mottled light-and-dark-green pattern and distorted growth.
- Plants may become stunted
- Fruit can be misshapen or mottled
- Aphids can spread the virus quickly
What to do
Remove infected plants, control nearby weeds, and avoid handling healthy plants after touching symptomatic foliage. There is no cure once a plant is infected.
Angular yellow patches form between leaf veins, often with gray growth below.
- Symptoms develop rapidly in humid weather
- Leaf undersides may look gray or purple
- Severe infections cause leaves to brown
What to do
Improve airflow, water at soil level, remove badly infected leaves, and avoid working among wet plants. Use a crop-labeled treatment only when needed.
Brassicas wilt or remain stunted because their roots become swollen and distorted.
- Plants may recover temporarily at night
- Roots develop club-shaped swellings
- Acidic, wet soil increases risk
What to do
Remove affected roots, improve drainage, test soil pH, and rotate away from brassicas for several years. Do not move contaminated soil to clean beds.
Orange, reddish, or brown powdery pustules appear on leaves and stems.
- Spots often begin on leaf undersides
- Foliage may yellow and drop early
- Warm, humid conditions encourage spread
What to do
Remove infected debris, provide generous spacing, water at the base, and rotate crops. Avoid saving seed from heavily infected bean plants.
Long gray-green or tan lesions spread along corn leaves.
- Lesions may look cigar-shaped
- Lower leaves can be affected first
- Crop residue can carry disease forward
What to do
Rotate crops, remove or thoroughly incorporate infected residue, improve airflow, and avoid overhead irrigation. Plant resistant hybrids when blight is recurring.
Plants remain stunted or wilt while roots develop bead-like knots or galls.
- Symptoms worsen during hot weather
- Damage often appears in garden patches
- Roots show distinctive swellings
What to do
Remove affected roots, rotate with non-host crops, control weeds, and consider soil solarization in warm climates. Resistant cultivars can reduce future losses.
Large green caterpillars rapidly strip leaves from tomato-family crops.
- Dark droppings collect below feeding sites
- Stems may be bare near the top
- The caterpillar blends into foliage
What to do
Handpick caterpillars, inspect plants daily, and leave hornworms carrying white parasitoid-wasp cocoons in place. Bt works best on small caterpillars when label directions are followed.
Small yellow-and-black beetles chew seedlings, flowers, leaves, and fruit.
- Beetles may be striped or spotted
- Seedlings can be destroyed quickly
- They can spread bacterial wilt
What to do
Use insect netting until flowering, remove nearby cucurbit weeds, and scout young plants frequently. Remove wilted plants and use only crop-labeled controls.
Leaves develop fine pale stippling, bronzing, and delicate webbing.
- Tiny mites gather beneath leaves
- Hot, dry weather favors outbreaks
- Heavily damaged leaves become crisp
What to do
Rinse leaf undersides, reduce plant stress, remove badly infested foliage, and protect predatory insects. Insecticidal soap must contact mites directly.
Irregular holes and shiny slime trails appear after damp nights.
- Damage is worst near the soil surface
- Pests hide beneath boards and debris
- Seedlings and leafy crops are vulnerable
What to do
Remove hiding places, water early in the day, handpick after dark, and use barriers or crop-labeled baits when necessary.
No close matches yet
Try a broader symptom, select “All crops,” or search for a visible clue such as “white powder” or “small holes.”
Before you treat
Inspect the whole plant.
A good diagnosis depends on location, pattern, timing, and recent weather. Check several plants rather than relying on a single leaf.
Browse Urban Farmer growing guides →Where did it begin?New growth, old leaves, fruit, stems, roots, or the entire plant?
2What pattern do you see?One plant, one row, scattered plants, or the whole garden?
3What changed recently?Rain, heat, watering, fertilizer, transplanting, or chemical exposure?
4Can you find the cause?Inspect both sides of leaves and look closely at stems and nearby soil.
Important: Similar symptoms can have different causes. Confirm the problem before applying pesticides or fertilizer, always follow product labels, and contact your local Cooperative Extension office when a problem is severe or uncertain.