The Online Gardener's Handbook 2010
Chapter 4: Vegetables
Tomato

Table of Contents

  1. Introduction
  2. Anthracnose
  3. Bacterial Speck
  4. Blossom-End Rot
  5. Early and Late Blight
  6. Tomato Leaf Roll
  7. Tomato Hornworms
  8. Sap Beetles
  9. Septoria Leaf Spot or Blight
  10. Whiteflies
  11. Learn More

Introduction

In this chapter, a description of various tomato pests will be provided along with suggested management options. These management options will not include the use of pesticides. Some biopesticides and certain reduced risk pesticides are still available to the homeowner for controlling weeds and pests in lawns and gardens. For more information, refer to Chapter 2 of this handbook and the Ministry of the Environment's website. For suggestions on managing specific weeds and pests, consult local horticulturalists, Master Gardeners or your local garden supply centre.

Anthracnose

Anthracnose fungi is a fungal disease that attacks the fruit. It persists in soil and crop residue and cause sunken, circular spots that may completely rot the fruit. Spots usually occur late in the season during cooler, wet weather on ripe fruit in contact with the soil.

Management Options

Keep tomatoes staked so that fruit is off the ground. Mulching will also help keep fruit from touching the soil. Avoid overhead watering, especially late in the season. Remove and destroy infected plant material. Rotate out of solanaceous crops for as long as possible.

Bacterial Speck

Tiny black specks appear on leaves and fruit. Fruit is infected while green but the black lesions remain until harvest. The fruit will be edible but unsightly.

Management Options

Purchase disease-free seed or transplants. Ensure transplants have no symptoms prior to planting. Follow proper watering practices and avoid working in garden when plants are wet. Grow in a sunny area of the garden.

Blossom-End Rot

Blossom-end rot is a very common disorder, especially on early developing fruit. Injury is due to a localized calcium deficiency in the fruit developed when hot, dry weather alternates with periods of heavy rainfall. The cause is primarily the dry soil and not a lack of calcium in the soil. Rot is brown to black becoming hard and leathery and occurs on blossom end of fruit. Later, fungi or bacteria may enter and cause soft rot of entire fruit. Excessive use of fertilizer, particularly nitrogen, may increase this disorder.

Management Options

Mulch and water carefully to maintain uniform soil moisture. Do not use too much fertilizer as excessive nitrogen upsets the supply of calcium to the developing fruit.

Early and Late Blight

Early blight occurs annually in tomatoes in most areas of Ontario by midsummer. Late blight fungus occasionally appears on tomatoes, and when it does it can have a very significant impact. For more information and management options refer to Potatoes.

Management Options

Refer to potato section for more management options.

Tomato Leaf Roll

Symptoms are rolled edges of the leaves but the foliage retains a healthy green colour. It is not a disease caused by fungus, bacterium or virus, but it is an internal disorder of the plant probably due to irregular water supply or severe root-pruning. It has no adverse effect on plant growth.

Management Options

This disorder can be associated with plant stress. Ensure soil fertility and moisture are adequate.

Tomato Hornworms

Tomato hornworms are large, green, robust caterpillars up to 10 cm long with diagonal white stripes on sides, and a black horn on the hind end. Leaves are eaten, leaving midrib. Holes are eaten in green fruit. Hornworm excretions are often visible near the injury. Larvae develop in summer, pupating in soil late in the season.

Management Options

Search for larvae near injury, hand-pick and destroy. Rototilling after harvest can help to destroy pupating hornworms in the soil. There are a number of natural parasites of this insects.

Sap Beetles

Sap beetles invade damaged tomato fruit in great numbers. They are small black beetles with four cream-coloured markings.

Management Options

Gather and discard damaged fruit. Use halves of overripe melon or bananas as bait. Remove bait regularly and destroy beetles with old bait.

Septoria Leaf Spot or Blight

Septoria leaf spot or blight has been a common problem in recent years. Spots are reddish at first but later develop grey centres with black dots. Spots will occur on the stems and branches.

Management Options

Purchase hot-water treated seed. Follow garden sanitation procedures.

Whiteflies

The adults are small white insects that cause little feeding damage but lay masses of eggs. The scale-like nymphs (juvenile stage) are sap suckers and cause leaves to wither. In addition, the production of sticky honeydew by the feeding nymphs usually leads to the growth of sooty mould.

Whiteflies multiply quickly, which makes control difficult. Swarms of small white flies are noticeable when plants are disturbed, and nymphs are found in large numbers only on the underside of leaves.

Management Options

When populations are small, vigilantly remove whiteflies by removal of infested leaves, vacuuming off leaves, or hosing leaves with water. Sticky traps can be used monitor whiteflies and may reduce numbers somewhat. Aluminum foil or reflective plastic mulches is thought to repel whiteflies from smaller plants.

Learn More

 


For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca
Author: OMAFRA Staff
Creation Date: 25 July 2005
Last Reviewed: 25 June 2010