The Online Gardener's Handbook
Chapter 4: Vegetables
Table of Contents
- Bacterial Speck
- Blossom-End Rot
- Early and Late Blight
- Tomato Leaf Roll
- Tomato Hornworms
- Sap Beetles
- Septoria Leaf Spot or Blight
- Learn More
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 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
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.
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.
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 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.
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.
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.
This disorder can be associated with plant stress. Ensure soil
fertility and moisture are adequate.
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.
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 invade damaged tomato fruit in great numbers. They
are small black beetles with four cream-coloured markings.
Gather and discard damaged fruit. Use halves of overripe melon
or bananas as bait. Remove bait regularly and destroy beetles with
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.
Purchase hot-water treated seed. Follow garden sanitation procedures.
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.
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.