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pecan disesaes South heavy rains fungicides scab
<p> PECAN&#39;S No. 1 enemy, scab, flooded pecan orchards throughout Georgia this summer. Growers in the country&rsquo;s leading pecan-producing state scrambled to get into orchards to apply timely fungicides to stay ahead of it, but it will cut yields this year.</p>

Pecan disease worst in recent memory

Heavy rains swamped pecan orchards all summer and left them vulnerable to the crop&#39;s No. 1 enemy: scab. Scab is reported to be the worst in decades in some locations where growers had a difficult time getting into orchards to apply fungicides. Before the scab outbreak, Georgia expected 80 million to 90 million pounds this harvest, but disease might claim 15 million pounds or more of that. &nbsp;

The last time Tom Stevenson remembers pecan disease being as bad as this year was in 1994, when a tropical storm stalled over south Georgia and dumped record rainfall in 24 hours – deadly flooding followed it.

In the region left swamped, growers were unable to get into orchards to work.

Though not deadly, record soggy weather dominated the Southeast in many areas this summer. It left pecan orchards vulnerable for a big attack from the crop’s No. 1 enemy. The fungal disease scab scars husks, cuts yield and hurts quality.

“We’ve had some wet years before, but not like it has been this summer where it has rained all summer long,” said Stevenson, a south Georgia-based pecan orchard manager.

Stevenson has managed pecan orchards for 40 years and currently oversees 5,000 acres. This year, he said, to try and stay ahead of the disease, his orchards got 16 or 17 fungicide sprays, or twice as much as in a normal year, costing $600 per acre this year for fungicide applications. Again, that cost is double what it is typically.


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“(Producers) will need to watch for (scab) next year, too, because there will be plenty of inoculum out there to over-winter on the tree limbs and if we get a warm, wet spring next year, they will need to get out there early to spray because there is no magic juice to spray to kill it and it is hard to play catch up with it once it starts,” Stevenson said.

Georgia’s the top pecan-producing state. Roughly half the state’s 150,000 acres of commercial orchards are planted in scab-susceptible varieties, like Desirable, Schley and Pawnee, said Lenny Wells, University of Georgia Cooperative Extension pecan specialist. The Desirable variety produces the desired nut quality and size the market likes most now.

Some growers, Wells said, sprayed upwards of 20 times to try and stay ahead of the disease this summer. If more than 25 percent of a pecan shuck is covered in scab, there will be losses. But when it hits a small, developing nut early, and if it is not managed or can’t be managed on a timely schedule, the nut turns black and falls. “Scab statewide is the worst it has been in 10 years at least,” he said. “And in some locations it is worse.”

Weather conditions in 2013 much like 2003

Scab claimed about 20 percent of the crop in 2003. Wells pulled weather data from April through August in 2003 and compared it to the same timeframe in 2013. “It’s almost identical data when you compare 2003 and 2013 with both rain amounts and frequency,” Wells said. During the timeframe, it rained more than 25 inches with as many as 75 days of rain in some locations in Georgia.

Pecan trees are alternate-bearing, meaning they produce a full crop every other year. Most trees in Georgia are on the same cycle, and this is an "off" year for Georgia pecans. Earlier in the spring, the crop looked set to make 80 million to 90 million pounds. But with the rainy weather and scab problems, Wells figures that potential statewide production likely will fall between 65 million and 70 million pounds by the time harvest ends later this year. Georgia’s record is 150 million pounds, set in both 1993 and 2007.

But unlike 2003, though, growers have more products and better practices to fight scab, even in bad years, Wells said. And, most importantly, growers have a bigger incentive to fight the disease to max out yields. “A lot of it now is nuts are worth more and growers are more willing to spend money on them,” he said.

The U.S. pecan industry has hit a boom in recent years with exports to China now vying for near half of the U.S. production each year. Where once prices fell into a production-driven boom or bust cycle, steady high prices, or $2 to $2.50 per pound, have put orchard management on the front burner for established growers and those looking to expand in it.

Pecan is a relatively small part of the United States farming economy, but it is big business in Southern states, particularly Georgia where it is worth more than $250 million annually and growing. Georgia is set to remain the top pecan-producing state. Nurseries that supply new trees are booked up until 2015, which means in the next two years acreage in Georgia could jump another 20,000 acres.

Nuclear year for disease

Getting ready for a Florida pecan grower meeting in early September, Tim Brenneman pulled a picture of a nuclear bomb explosion up on his computer screen. Said he was going to start his presentation on the 2013 pecan year with that picture to describe what scab has been this year. “It’s been a nuclear year as far as scab explosion,” said the UGA plant pathologist based in Tifton, Ga.

“A year like this will show weaknesses in the system. I think we do a good job on scab control, but in a year like this one growers can see what isn’t working,” he said.

For example, on his travels around the pecan-growing region in Georgia it is not hard to see how well or bad spray coverage has been for fungicide treatments. Many locations have scab prevalent in the upper canopies where spray booms didn’t reach.

Pecan growers have good chemistries to fight scab with several modes of action, including strobilurin, triazole, triphenyltin hydroxide, organotin. Plus, an old tried-and-true chemistry called dodine is once again working on scab in Georgia, where growers stopped using it many years ago because it had lost some effect on the disease. But it seems to be working again, especially in combination with the other chemistries.

Brenneman is now working with a new chemistry that is not yet labeled for pecans, but he says it “shows great promise” in fighting the disease and hopes it will soon be labeled for pecans.


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