Department of Botany and Plant Pathology
Lilly Hall of Life Sciences
Plant Disease control
BP-3

FIVE STEPS FOR HEALTHY GARDEN TOMATOES
R. X. Latin, Extension Plant Pathologist

Gardeners generally spend much time and
labor planting tomatoes each spring anticipating
a bountiful harvest. Unfortunately, the harvest
often falls far short of expectations because dis-
eases have ruined the crop. Of six diseases that
plague Indiana’s tomato gardeners year after year,
five (early blight, Septoria leaf spot, anthracnose,
Fusarium wilt, and Verticillium wilt) are caused
by fungi common to garden soils. The sixth
(blossom-end rot) is a physiological disease related
to the climate and garden environment. Although
the parasitic fungi in the garden and the midwest
climate cannot be avoided, good yields can be
achieved with proper planning and preparation
before planting and careful attention to the plants
afterward.

The guidelines for producing healthy plants
and good yields include: 1) using resistant varie-
ties, 2) tilling and fertilizing the garden properly,
3) providing adequate water, 4) using fungicides as
needed, and 5) cleaning up the garden in autumn.
These five steps for producing healthy tomatoes
are discussed in detail, following a brief descrip-
tion of the diseases.
The Diseases

Anthracnose

Key symptoms of anthracnose infection appear
as sunken, circular spots on ripe fruit (Figure 1).
The sunken areas can range from 1/4 to 3/4 inch in
diameter. Older anthracnose infections frequently
lead the way to soft rot, making the fruit totally
unusable. The fungus can overwinter on plant
debris in the garden. Disease may be spread to
healthy fruits via rain-splashed or airborne spores
produced by the fungus.

Early blight

Early blight infections are most noticeable as
circular or irregularly shaped brown spots on
tomato foliage (Figure 2). A closer look at the spots
will reveal target-like rings or concentric circles
within the brown area. The early blight fungus is
most likely to attack stressed plants or plant parts.
Hence, older leaves are usually the first to show
symptoms on apparently healthy plants. Also,
plants stressed by other diseases, nitrogen defi-
ciency, drought, or too much water succumb to
early blight infection sooner than do more vigor-
ous plants. The fungus can overwinter on infested
residue in the garden. Disease is spread via air-
borne spores and is favored by warm, wet weather.
Under favorable environmental conditions early
blight will defoliate plants in a few weeks, making
ripe fruit more prone to anthracnose infection.

Septoria leaf spot

Leaves with small circular spots (1/16 to 1/8
inch in diameter with gray centers and darker
margins) are typical of those infected with the Sep-
toria leaf spot fungus (Figure 3). Like early blight,
Septoria attacks less vigorous plants and plant
parts. On a single plant the disease can progress
rapidly from lower foliage to new growth in cool,
wet weather. The fungus can overwinter on infested
residue in the garden. Splashing rain is largely
responsible for spreading spores from plant to
plant.

Fusarium wilt

Fusarium wilt is caused by a fungus which can
inhabit almost all soils. Plants can be infected at
all stages of development. Young seedlings infected
by the fungus result in damped-off seedlings.

Cooperative Extension Service • Purdue University • West Lafayette, Indiana