Randy S. Sanderlin, Hall, Michael J., Coolman, Denise | 9/29/2005 2:46:40 AM
SHREVEPORT – Growers learned how to detect and control the most economically damaging disease for pecan production in the South during the LSU AgCenter’s Pecan Research and Extension Station Field Day last week (Sept. 22).
Known as pecan scab disease, experts said it reduces pecan production and profits.
"This disease affects stem, leaf and nut growth, causing a reduction in yields," said Dr. Randy Sanderlin, an LSU AgCenter plant pathologist at the station. "It is often the cause of lower production and lower profit in commercial orchards."
Pecan scab disease is caused by the fungal pathogen Cladosporium caryigenum. The disease is detected by lesions, which generally are circular and grow as much as about ¼ inch in diameter. The lesions are light brown to black and are found along the veins as well as other parts of the leaves. Severe infection can kill stem growth, experts explained.
"Lesions on nuts become sunken and often harden as they crack with age," Sanderlin said. "Severely infected nuts can become distorted and stop growing."
Depending on nut stage development and severity of the infection, damage can result from a little loss of yield to total nut loss, he said.
According to Sanderlin, weather plays a big part in the severity of pecan scab disease.
"Moisture is needed for spore germination and infection," he said, adding, "Several hours of wetness are needed for infections to become established."
Other factors that play into an orchard getting a pecan scab disease infection include temperature and the cultivar that is planted.
Fungicides are used to control the disease, and Sanderlin suggested growers use ground equipment to apply fungicides at a concentration sufficient to prevent infection and completely cover the trees. For the proper concentration, use the amount advised by the manufacturer on the product label.
"Generally, fungicides should be applied every two to four weeks from spring through summer," he said.
In noncommercial orchards, such as small home orchards and yard trees, it may be more feasible to reduce the level of pecan scab disease by "cleaning up" the orchard, Sanderlin said.
"Remove old leaf and nut debris from the ground, or plow the debris under," Sanderlin said. "Shucks remaining in the tree at the end of a year should be removed and infected stems pruned away."
Bacterial leaf scorch was another disease covered during the field day. Sanderlin talked about how growers may be able to delay or reduce the amount of the bacterial leaf scorch disease in an orchard by grafting.
"Before any grafting is done, however, growers must be sure to check all wood for the disease," Sanderlin warned. "Once the bacterium is in a tree, it stays in the tree. Growers have to avoid this disease to start with."
Growers must also be on the lookout for insects. Dr. Mike Hall, an LSU AgCenter entomologist at the pecan station, talked about a series of trials being conducted for pecan nut casebearers.
"What you want to do with this insect is prevent the larvae from growing into adults," Hall said. "We’ve found using a growth regulator early in the year helps."
Trap crops are used at the Pecan Research and Extension Station to control late season pests. Soybeans and grain sorghum are some trap crops used.
"Grow the trap crop around the perimeter of the orchard," Hall said. "Monitor the trap crop so that you will know what and how many pests are in the orchard before starting a spray regimen."
In addition to these topics, field day participants also heard about a new orchard that has been planted at the station. This orchard is being used to help scientists at the station evaluate the economics involved in establishing and maintaining a new orchard.
Hedging pecan trees was another topic covered, and participants also were told about information that can be found at the LSU AgCenter station’s Web site.
Pecan growers from all over the South make the annual trek to the field day. Ben Littlepage of Colfax and Patsy Hawkins of Foreman, Ark., are two pecan growers who said they "never miss a field day" at the station, adding that the information provided is very important in helping them grow more profitable orchards.
"I started growing pecan trees in the 1940s," Littlepage said. "I have always depended on the research done by the LSU AgCenter to help me grow my crops."
"All of this information is very helpful to us," she said. "This (research station) is where we go whenever we have a question. I don’t know where we’d be without the research station and its researchers."
Mike Hall at (318) 797-8034 or firstname.lastname@example.org
Randy Sanderlin at (318) 797-8034 or email@example.com
A. Denise Coolman at (318) 547-0921 or firstname.lastname@example.org