June 30, 2004 | By: Laura Skillman

Above normal rainfall this spring brought with it increased chances of disease on many fruit trees in Kentucky . The rains also made protecting trees difficult at times, but the rewards should be great.

Growers who were able to apply fungicides in a timely way are having good success in disease management, but unsprayed trees or those which failed to receive critical sprays are showing numerous symptoms, said John Hartman, plant pathologist with the University of Kentucky College of Agriculture.

Luckily, it looks like most people were able to beat back the disease problems and the apples and peaches are looking good.

“It’s looking like a really good fruit crop this year,” said John Strang, UK Extension fruit specialist. “The fruit size is up.”

But the year has been a challenge.

“This year’s been tough for spraying and weed control and the rain has leached nitrogen out of the soil in many cases,” Strang said.

Cedar-apple rust, apple scab, powdery mildew and frogeye leaf spot have shown up on apple trees this spring while fire blight was not too bad. The threat of some of these diseases has passed, such as cedar-apple rust and fire blight, but others can continue to be an issue throughout the season, Hartman said.

Weather data was collected and apple scab disease forecasting programs at the UK Research and Education Center in Princeton, and in Lexington at the UK Horticultural Research Farm this spring, showed eight periods in which severe apple scab infections likely occurred.

At least three of these eight infection periods lasted 85 or more intermittent hours at temperatures where 15 or 20 hours would have sufficed to favor severe infections. Producers who did not gain control of this disease during the primary infection periods will see secondary infection cycles throughout the growing season, Hartman said.

For peach growers, now is the critical time for controlling fruit scab and peach brown rot, he said.

Fruit will sweeten up more with dryer growing conditions.

“Cloudy weather reduces photosynthesis which makes the sugars. In addition, rain will increase the fruit size but dilute the concentration of fruit sugars,” Strang said.

Since conditions vary across the state, growers need to manage their apple and peach trees based on what’s occurring in their orchards, Hartman said. Guidelines to assist growers in their management can be found in the UK Cooperative Extension Service’s 2004 Commercial Tree Fruit Spray Guide and the Midwest Tree Fruit Handbook, available at county Extension offices.



Editor: Laura Skillman 270-365-7541 ext. 278
Source: John Strang 859-257-5685; John Hartman, 859-257-7445 ext. 80720