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University of Minnesota Extension

Quick guide to insects and diseases of tomatoes

Quick facts

  • This page highlights non-chemical practices to prevent or manage common insect and disease problems of tomatoes. 
  • For more detailed information follow the links in each section.
  • Click on an image to enlarge it.
  • See Growing healthy vegetables for more detailed information on how to keep your garden disease and pest free.

Preventing leaf spot and fruit rot diseases

Septoria leaf spot
  • Plant tomatoes where no tomatoes, potatoes, peppers or eggplants have been for the past 3-4 years.
  • Keep tomato leaves as dry as possible.
    • Water with drip irrigation or a soaker hose.
    • Water in the morning so leaves dry quickly in the sun.
    • Stake or cage plants.
    • Space plants so that air flows between them.
  • Mulch all exposed soil with plastic or organic mulch.
  • Scout tomato plants once a week.
    • Look at lower leaves for leaf spots.
    • Remove infected leaves and rotten fruit from the garden.
  • Remove or bury tomato plants at the end of the season.

More information on early blight of tomato.

More information on bacterial spot of tomato.

Blossom end rot

Brown, mushy patch on the bottom end of two tomatoes
  • Irrigate to keep soil moisture even.
  • Mulch the soil to maintain soil moisture.
  • Don't use too much fertilizer, especially nitrogen.
  • Avoid damaging roots. Don't dig or cultivate for weeds close to the plant.

More information on blossom end rot.

Viral diseases

  • Remove and destroy infected plants.
  • Remove weeds in the field.
  • Clean tools and hands after touching infected plants.

More information on tomato viruses.


  • Remove weeds and plant residue.
  • Till garden before planting.
  • Place cardboard collars or aluminum foil around plant stems when planting transplants.

More information on cutworms.


Flea beetles

  • Plant as late as possible.
  • Cover plants with a row cover (light weight fabric — remove when tomatoes are flowering).
  • Plant a trap crop, like radish, before tomatoes.

More information on flea beetles.

Tiny, black beetles feeding on a green leaf with several holes





Reviewed in 2019

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