By Sharon Omahen
University of Georgia
With production expected to reach 90 million pounds this year, Georgia pecan growers have a lot to smile about. They still frown, however, at the mention of pecan scab.
Each year the state's growers spend $200 to $300 per acre on fungal sprays to fight pecan scab. The disease develops and spreads in wet weather, particularly when the nuts are growing.
Nuts infected with pecan scab develop black spots on the shuck. Many will be so covered that the entire nut turns black and falls before it's fully developed.
Existing cultivars losing resistance
For decades, commercial growers have relied on just two varieties, Stuart and Desirable, for most of their pecan crop.
"Stuart was selected in the 1880s, and Desirable came along in the 1930s," said Patrick Conner, a pecan breeder with the University of Georgia College of Agricultural and Environmental Sciences.
Both had good resistance to pecan scab when they were first selected. Decades later, though, both are now very susceptible to the disease.
"Over time, the scab fungus adapted and overcame their resistance," he said. "Lately, scab has been very difficult to control on these varieties, even with fungicide sprays."
Working closely with state's growers
Conner became the UGA pecan breeder in 1998 after the state's pecan commission rallied for the position. From his Tifton, Ga., laboratory, he works closely with growers to develop new varieties.
When growers find what appears to be disease-resistant pecan seedlings in their orchards, they bring them to Conner.
"When we find one that has good qualities, we put it through research trials alongside our crosses and see if it has potential to be a new variety," he said.
Conner recently got a $6,000 grant from the Georgia Pecan Commodity Commission. The grant will help fund his search for new disease-resistant pecan varieties.
"When it comes to commercial nuts, size is a major factor, because people like larger pecans," Conner said. "The percent kernel, or the way the kernel fills out the nut, is also essential."
Pecan breeding takes time
Each spring since 1999, Conner has made new pecan crosses. His first crosses, or potential new varieties, have just begun to flower. Next year they will produce their first crop of nuts.
Conner says the breeding program works in two phases. First, he evaluates seedlings for disease resistance and overall nut quality. This first phase takes five to 10 years.
The selections that pass this phase are then reproduced and inspected for other qualities, like tree productivity and regular bearing. This phase of the breeding program takes about 15 years.
"Once we get the program running, we'll be releasing new varieties every few years," he said. "We hope to have our first new resistant variety from our crosses in 15 to 20 years."
In the interim, Conner is evaluating selections from Georgia growers, Auburn University researchers and the U.S. Department of Agriculture breeding program in Texas.
"There's a USDA selection we're testing that looks good," he said. "We're sending it out to selected Georgia growers this spring to try. It's so new it's referred to by a number, 70-6-15. It appears to have very good quality and disease resistance."
Growers have to look way down the row to see the help on the horizon. "In the future, hopefully, growers will be able to plant new, improved varieties when they replace trees," Conner said, "rather than continuing to plant the same variety over and over."
For the meantime, Georgia growers keep waiting, and Conner keeps focusing on daily accomplishments.
"It's (breeding pecan varieties) definitely a long process," he said. "But once you get a variety, the benefits will be long-term."
(Sharon Omahen is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.)