Troubleshooting Tomato Problems: Diagnose and Treat Common Issues

What's Wrong With My Tomatoes?

Fresh, vine-ripened tomatoes are a summer joy, but diseases, pests, and environmental stresses can derail your harvest. The best defense: start with healthy plants in full sun, keep soil evenly moist, and provide steady nutrients. At planting, add granular tomato fertilizer (e.g., Gardener's Best Organic Tomato Fertilizer). During growth, use water-soluble fertilizer (e.g., Plant Health Care). Even well-cared plants can have problems. Diagnose first—disease, insect, or environment? Here are common issues and solutions.

Blossom-End Rot

Symptom: Black sunken areas on blossom end of fruit.
Cause: Calcium deficiency, aggravated by drought/uneven watering, root damage, excess nitrogen.
Solution: Keep soil consistently moist; apply thick straw mulch. Use Rot-Stop (all-natural spray). Usually affects only early fruits.

Poor Fruit Set (Few Flowers or Flowers Drop)

Causes: Night temps >70°F or <50°F; day temps >85°F; drought stress; excess nitrogen; too little sun.
Solution: Most common cause is temperature—problem resolves when weather improves.

Early Blight

Symptom: Dark, concentric rings on lower leaves and stems.
Solution: Spray Actinovate or Copper Fungicide. Avoid wetting leaves when watering; don't handle wet plants.

Late Blight

Symptom: Water-soaked patches/lesions on stems, foliage, fruit. Spreads rapidly via wind-dispersed spores.
Solution: Track outbreaks at usablight.org. When detected in your region, spray preventively with Actinovate or Copper Fungicide. Infected plants must be destroyed.

Fruit Cracking

Cause: Uneven watering.
Solution: Use soaker hose (e.g., Snip-n-Drip Soaker System) to moisten entire root zone. Mulch to retain moisture.

Yellowed, Distorted, Curled Leaves

Possible aphids: Check leaf undersides and new growth. Blast with strong water jet or apply neem oil.
Possible tobacco mosaic virus: Wash hands thoroughly after smoking/tobacco use before gardening. Remove and discard infected plants (do not compost).

Wilting Foliage

Underwatering: Water deeply; should recover in 24 hrs.
Fusarium wilt: Lower leaves wilt, plants stunted, don't recover after watering. Remove and discard (do not compost).

Holes in Leaves and Fruit

Tomato hornworm: Large caterpillar with white diagonal stripes and black horn. Handpick (drop in soapy water).
Slugs: Use iron phosphate slug pellets and beneficial nematodes.

Small Holes in Fruit / Collapsing Tomatoes

Tomato fruitworm: Moth larvae bore into fruit, consume from within. Once inside, only remedy is destroying infected fruit. If severe, start plants under row covers; keep covered until flowering.

Problems vary by soil, climate, and local outbreaks. Consult your cooperative extension for region-specific advice.