Published on 07/23/01

Rain Mixed Blessing for Georgia Peach Crop

This summer, timely rains have helped Georgia farmers recover from three years of severe drought. Peach growers, however, know too much of a good thing can bring a whole new set of problems.

This season, peach producers face the worst disease problems in years, said Phil Brannen, an Extension Service plant pathologist with the University of Georgia College of Agricultural and Environmental Sciences.

Extended, frequent rain has caused long stretches of moist, soggy conditions, he said. These have opened the gate for diseases, causing fungi and bacteria to thrive and attack Georgia's $24 million peach crop.

"This year, we had nearly perfect conditions for dissemination of spores and subsequent germination," Brannen said.

Over the past three years, because of drier conditions, peach producers have had little worry with diseases, he said. But this year, diseases have consumed as much as 25 percent of some orchards.

The blight, the spot, the rot

A disease known as blossom blight entered orchards early in the growing season. This condition led the way for brown rot, a much more serious disease, to appear during harvest, he said.

Photo:Plant Pathology

Infected with brown rot, a peach hangs mummified from a tree in Peach County.

"We don't often have blossom blight," he said. "But we had wet conditions during bloom this year, and we had a goodly amount of infection during bloom. Spores were formed. . . . This set us up for a heavy brown rot year."

The brown rot fungus produces a multitude of spores which are spread from fruit to fruit by wind and rain, he said.

Brannen said brown rot has hit orchards in middle Georgia hardest. The disease mummifies the fruit on the tree.

"Mummified fruit is actually hard, and it follows with the complete rotting of the fruit," he said.

Wet, warm conditions make another disease, bacterial spot, more likely on certain varieties. O'Henry, a variety being picked right now, he said, is especially hard-hit.

Photo:Plant Pathology

Bacterial spot causes deep, ugly blemishes on peaches, rendering them unmarketable.

Bacterial spot will show up when the fruit is ripening.

"The bacterial spot makes a nasty-looking fruit," Brannen said. "It makes deep pits in the fruit. It's an ugly disease."

Bacterial spot has infected 15 percent to 20 percent of some orchards, he said.

Tough to control

Brown rot and bacterial spot are tough to control, Brannen said. "They (producers) are spraying as much as they can," he said.

When it rains as often as it has this season, the chemicals just simply wash off of the trees, he said. And it's hard to spray in heavily soaked orchards.

"To spray and then have to go right back in and spray again is almost impossible," he said.

In the past three or four weeks, it has gotten dry again. That may help, Brannen said. But the damage has already been done.

"Overall, we've had a good peach crop, good fruit set and prices have been good for producers," he said.

But when you consider the added cost of spraying and the reduction of sellable fruit due to disease, the harvest could have been much better, he said.

UGA CAES scientists are working to develop an effective spray management program for growers. The program will determine the best spraying times by monitoring the temperatures and moisture levels in orchards.

The peach harvest began in April and will last into mid-August

Brad Haire is the former news editor with the University of Georgia College of Agricultural and Environmental Sciences.