By William Terry Kelley
Georgia Extension Service
Volume XXVII
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There was a time a gardener could simply plant the same
tomato or squash variety
year after year with no problem. It usually tasted great, was
easy to grow or
was an heirloom variety handed down over the generations.
Those days are increasingly
gone.
More and more pesticides are removed from the market every
year, and home gardeners
have fewer options to control diseases and insects. It seems
that more plant
diseases become problematic each year. The need for varieties
to be resistant
gets more important all the time.
Unfortunately, those old heirloom varieties and many of the
best tasting ones
have little or no resistance to plant diseases. But with more
disease pressure
and fewer pesticide options, using varieties resistant to
plant diseases is
often the only option the gardener has to turn to.
Chief disesase
Chief among these diseases is tomato spotted wilt virus. Not a
problem in Georgia
until just a few years ago, TSWV has become the arch nemesis
of the home gardener.
This virus is a serious problem for commercial tomato growers.
But it’s an even
greater curse in the garden.
TSWV is transmitted by thrips to the tomato plant. The virus
is harbored by
so many plant species it doesn’t have trouble being available
to attack tomatoes
almost anywhere in the state.
The commercial grower has some pesticide options to manage
thrips, although
they are of questionable effectiveness. Famrers can use tools
such as reflective
plastic mulches, too, to deter thrips invasions. Over large
fields, these mulches
can confuse thrips and cause them to avoid the tomato
fields.
However, the home grower almost never has such options.
Fortunately, researchers
have begun developing some tomato varieties that are resistant
to TSWV.
Resistant options
About the only two gardeners can get now are similar varieties
called “BHN
444” and “BHN 555.” Both were developed by BHN
Genetics. The
555 variety is primarily for use in a fall or late-summer
crop, since it’s a
heat-set variety.
BHN 444 is more of a shipping-type tomato than a garden
variety. It generally
won’t have a usual tomato shape until it’s almost mature, and
it takes its time
getting ripe.
It may not have the flavor or texture of your usual
“Better Boy” or
“Rutgers,” but it may indeed be the only way you can
successfully
grow fresh tomatoes in the garden.
A couple of newer varieties may have better flavor and
shape, but don’t look
for them this season. Hopefully, continued research will yield
more of these
resistant varieties.
Squash susceptible, too
Much the same is true for squash. Four main viruses affect
squash. On yellow
squash, it’s easily distinguishable by the green coloration in
the fruit.
Some varieties now have resistance to two, three or even four
of these viruses.
Some varieties are not resistant, but contain the
“precocious gene”
which masks the green coloration in yellow squash. They still
get the virus,
but they don’t show the symptoms.
Many of these resistant varieties are on the market today.
Gardeners can tell
which are resistant or tolerant to virus by reading the
variety descriptions
in the seed catalogs. Not all seed companies market these
varieties, so you
may have to shop around.
There are other diseases to which varieties may be
resistant.
Price of resistance
Often, the price of having varietal resistance is the loss of
some quality or
flavor characteristics. However, plant breeders are constantly
working to improve
quality and include resistance.
Varietal resistance will become an ever-increasing part of
vegetable gardeners’
weapons against those dreaded disease pests.
