By Brad Haire
University of Georgia

Georgia’s row crops are enjoying some of the best weather
they’ve had in years. But major crop enemies dwell in those
healthy plant canopies. Plant diseases, too, enjoy the wet
weather.

Ample rainfall all spring and summer’s rising humidity have
made “super” weather for certain crop diseases, says Bob
Kemerait, a plant pathologist with the University of Georgia
Extension Service.

“We’re seeing a lot more fungal diseases in particular,” he
said. Fungal diseases can take their toll on major Georgia
crops, like corn, peanuts and cotton. Such damage to plants can
lead to lower yields.

Corn calls

“In the past few weeks, I’ve had more phone calls about corn
(diseases) than for cotton and peanuts combined,” he said.

The number of cotton and peanut calls hasn’t dropped from other
years. There’s just been an increase in corn diseases and
interest in controlling them this year, he said.

Southern corn leaf blight and southern rust attack corn leaves,
especially during periods of wet weather and on corn varieties
with reduced resistance. These diseases can easily take away
yield and cause serious damage when the crop is grown for
livestock feed, Kemerait said.

Fueled by wet, humid weather, these two diseases have
increasingly damaged Georgia’s corn in recent years. They cost
growers about $3 million in damage each year. The damage could
be greater this year, he said.

Corn diseases aren’t as economically damaging as cotton or
peanut diseases. But all together, they cause about $10 million
a year in damages.

Historically, corn farmers haven’t felt that the value of field
corn justified the expense of disease control. But that way of
thinking is changing, Kemerait said.

The Georgia Commodity Commission for Corn wants studies to
determine if farmers can afford to fight these diseases before
they get out of hand.

Funky peanuts

The wet weather may have helped Georgia’s peanut crop to look a
little more “funky” this year, he said. Symptoms are being
called funky leaf spot.

It looks similar to early leaf spot disease, but conventional
chemicals don’t appear to affect it much. Farmers and
researchers will continue to watch this disease, he said.

Tomato spotted wilt virus, a deadly peanut disease, may take it
easy this year, Kemerait said. It hasn’t been as severe on other
crops. This is usually good news for the peanut crop.

Farmers also stuck to the UGA Spotted Wilt Index, a guide
developed to reduce the risk of the disease, this season. In the
past, Georgia farmers had most of their peanuts planted before
May 15. But this year the risk index recommended not to start
planting before May 10.

But planting beginning in the middle of May means that the
peanut plants will likely have greater exposure to leaf spot
diseases, which tend to be more severe on later planted
peanuts.

Most farmers can keep leaf spot diseases at bay with regular
spraying, he said.

Georgia peanut farmers spend about $65 million fighting diseases
and still lose $50 million to disease damage each year.

Cotton worms

Wet weather blight affects cotton in periods of damp weather and
has appeared on much of the 2003 crop. However, it has
typically been only a short-lived cosmetic problem.

Nematodes, the microscopic worms that feed on cotton roots, have
shown up with a vengeance in some fields early this year,
Kemerait said.

The wet weather may provide a better environment for their
feeding and development, he said. However, poor crop rotation is
usually the reason that cotton growers have a problem in their
fields.

“The best thing farmers can do right now is to keep an eye on
their fields, know what’s going on and be ready (to fight
diseases if they appear),” Kemerait said.

But the best defense against diseases, he said, is having a
healthy plant. And, so far, nature has provided the weather for
that.