By Brad Haire

University of Georgia

Volume XXVIII Number 1 Page 3

Diseases can seriously damage or completely destroy a
vegetable garden. But
there are a few things the home gardener can do to reduce the
risk these veggie
enemies pose.

“Most vegetables are susceptible to a number of diseases,”
says David Langston,
a vegetable plant pathologist with the University of Georgia
College of Agricultural
and Environmental Sciences.

Types of problems and their causes

Wilts, leaf spots, blights and fruit rots, he says, are just
a few of the problems
that plague vegetable gardens every year.

Plant diseases are caused by four primary types of organisms:

1. fungi,
2. bacteria,
3. nematodes and
4. viruses.

When conditions are wet and temperatures warm, your vegetable
plants are more
susceptible to diseases caused by fungi and bacteria. Scout
your garden regularly.

When garden conditions are dry, nematode damage is more
evident. Soil may be
sampled for nematodes by submitting a sample through your
county extension office.

Viral diseases can occur at any time, he said.

Many plant diseases can be on or within seed. “Seeds should
not be saved from
year to year,” Langston said. “This is important to prevent a
number of diseases.”

Buy seed from a reputable dealer, because you can’t
distinguish healthy seed
from diseased seed. And make sure you follow directions on
when and how to plant
them.

Your best bet for control

Disease-resistant plant varieties are the most efficient way
of controlling
vegetable diseases. So buy resistant varieties when you can.
Resistance traits
are usually listed in seed catalogs and in plant stores.

Don’t plant your garden near or beneath trees. The shade will
reduce the drying
of plant foliage after rain and increase the chances of
diseases. Besides, vegetables
like a lot of sunlight, and the trees will compete for vital
nutrients.

Crop rotation is important. If you continue to plant the same
vegetables in
the same spot year after year, you’re asking for soil disease
problems.

Grow the same or closely related vegetable plants in the same
soil only once
every three to five years, Langston said. This practice
starves out most pathogens
that cause stem and leaf diseases.

Vegetable families include:

• Alliaceae (chives, garlic, leeks and onions).
• Brassicaceae (broccoli, Brussels sprouts, cabbage,
  cauliflower, collards,
  mustard, radish, rutabagas and turnips).
• Cucurbitaceae (cantaloupes, cucumbers, honeydew melons,
  pumpkins, squash
  and watermelons).
• Fabaceae (all beans, English peas and Southern peas).
• Solanaceae (eggplant, peppers, potatoes and
  tomatoes).
• Asteraceae (lettuce).
• Poaceae (corn).
• Malvaceae (okra).
• Chenopodiaceae (spinach)
• Apiaceae (carrots).

Everyday prevention

“Trap crops” can reduce virus diseases carried by small
insects. Plant a few
rows of a crop like rye or corn around your main garden. This
will tempt insects
to feed there first, reducing the risk of diseases some small
insects are known
to carry.

When watering, avoid splashing soil onto plant foliage. If
possible, irrigate
by running water between the rows. Use a mulch layer of straw,
bark, shredded
paper or plastic to keep soil from splashing onto plants and
keep fruit from
touching bare ground.

If you use tobacco, wash hands thoroughly before handling
plants. This will
prevent the spread of tobacco mosaic virus, which can infect
many kinds of vegetables,
particularly tomatoes and peppers.

After harvest, remove and destroy all plants from the garden,
and sanitize
your garden equipment. This will reduce the overwintering of
disease-causing
organisms.

Most important, use proper cultural practices to keep your
plants healthy.

“Healthy plants don’t get diseases as easily as weak ones,”
Langston said.
“Healthy plants are the best control against plant
diseases.”