CLEMSON — After two seasons of climatic events that lashed out at the state’s peach crop, South Carolina peach producers and researchers believe this season could be better.
“The peach crop looks very good this year,” said Juan Carlos Melgar, a Clemson assistant professor in the plant and environmental sciences department. “Many of the growers believe they are going to have a full crop, which, after the past two years, makes them very excited.”
February 2018, just as February 2017, was warmer than average, causing most varieties to bloom about two weeks earlier than normal. Then there was a late freeze that affected some of the early varieties, such as those harvested in May.
“It all depends on the location,” Melgar said. “For most growers, it is not a big loss, and because most varieties are coming a bit earlier, the increase of price will offset the small losses of those varieties for most growers.”
Melgar met just one grower who reported significant loss for these early varieties. Melgar attributes it to orchard location, noting most of the losses are associated with some of the early varieties.
Diseases
Peach diseases are a concern for many growers. Last year’s limited crop meant there was no need to aggressively manage pests and diseases. This caused an increase of scale, bacterial canker and many fungal spores, leaving no room for error this season.
“In some areas we are seeing premature peach tree decline due to bacterial and fungal infections from last fall” said Guido Schnabel, a Clemson plant pathologist. “The perfect storm of high disease pressure, optimal infection conditions and tree wounds generated at leaf abscission zones created problems that now result in limb dieback and even tree death in some instances.”
One disease that cannot be sprayed for is Armillaria root rot. A Clemson University team led by horticulturist Gregory Reighard, peach breeder Ksenija Gasic and Schnabel is working to find solutions for both short- and long-term Armillaria root rot in peaches.
The most current, effective way to manage this disease is to prevent trunk infection by planting peach trees shallow on berms that are three-feet wide and 18 inches high. Ideally, the first few inches of the roots are excavated after two years so that the pathogen cannot proceed from infected roots to the tree. This study involves peach trees planted on berms at Clemson’s Musser Fruit Research Center.
“We are using a modified levee plow to make the berms,” Schnabel said. “We added a roller bar so that the berms would be at the height we wanted and the tops would be flat.
Flat tops on berms are used to determine optimal row height.
“If the roller doesn’t touch the soil, the berm isn’t high enough,” Schnabel said.
The modified plow was used to plant more than 600 acres of peaches during the 2017 season, mostly on private lands.
Clemson researchers also are working on long-term solutions with scientists from Michigan State University and the University of Georgia. This grant is administered through the Pennsylvania Department of Agriculture.
“This research is funded by a Specialty Crop Multi-State Program grant we received from the United States Department of Agriculture in 2016,” Gasic said.
Insect pests
Peach growers also should keep a vigilant watch for insects that may attack their crops. Brett Blaauw, assistant professor and Cooperative Extension specialist for Clemson and the University of Georgia, said insect pests to look out for in this year’s peach crop include scale insects, such as San Jose scale and white peach scale, as well as borers.
“San Jose scale has been increasing in numbers and severity over the past decade and does not appear to be slowing down,” Blaauw said. “With last year’s widespread crop loss, insect pest management in orchards with severe crop loss likely was neglected or reduced. Seasonal cover spray applications may have been reduced in some areas last year, which may have resulted in an increase in borer infestations.”
Scale insects and peach tree borers attack trees and not fruit, Blaauw said. This can lead to significant injury to trees, including twig or limb die-back and even total tree loss if these insect populations reach high levels. Orchards heavily infested by lesser peach tree borer suffer reduced fruit size and yield.
To help reduce the effects of scale insects, Blaauw said infested branches and limbs should be pruned, removed and destroyed. Growers also should apply horticultural oil as a dormant and as a delayed-dormant application to every acre of peaches every year, he said. Coverage with the oil is crucial for effective scale control. The addition of an insecticide, such as chlorpyrifos, or an insect grower regulator, with the delayed-dormant application can improve early season control of scale. Additional applications of insecticides later in the season may be needed if populations continue to grow. The most effective lesser peach tree borer control programs rely on a combination of a preventative chlorpyrifos spray applied at delayed-dormant, followed by a full-season cover spray program.
Organic growers can utilize the same pruning and horticultural oil applications. Additionally, a new mating disruption formulation for the southeastern United States has been developed, tested and is now registered for South Carolina and Georgia. While the results are highly encouraging, for the most effective control of borers mating disruption should be implemented on a large-scale area of peaches.
“Lesser peach tree borers need rough surface, such as cracked or peeling bark, to lay their eggs on, so for both organic and conventional growers it is important to keep the trees healthy and the bark intact,” Blaauw said. “This can significantly reduce the chances of borer infestations.”
Peach growers in the southeastern United States can learn more about pest management from the 2018 Southeastern Peach, Nectarine and Plum Pest Management and Cultural Guide, http://bit.ly/PeachGuide.
Growers also can get quick, up-to-date information about fruit crop diseases, pests and disorders, from a series of apps, MyIPM Smartphone App Series, available in the Apple Store and Google Play at no cost.
China tariffs
A recent dueling of taxes between the United States and China has resulted in China placing tariffs on more than 100 U.S. imports, including pork, fruit and wine. But Nathan Smith, a Clemson Extension professor of agribusiness production and an Extension economist, said South Carolina peach growers need not worry about these trade disputes between the U.S. and China. South Carolina exports very few peaches.
“South Carolina’s peach production is for the U.S. fresh market,” Smith said. “The effect of the tariffs on our peaches would be minimal if any.”
Peach statistics
South Carolina is the second highest peach production state behind California, with Georgia and New Jersey following. Statistics from the United States Department of Agriculture National Agricultural Statistics Service show South Carolina produced: 110,050 tons of peaches in 2010; 95,015 tons of peaches in 2011; 74,970 tons of peaches in 2012; 69,720 tons of peaches in 2013; 65,660 tons of peaches in 2014; 68,880 tons of peaches in 2015 and 52,800 tons of peaches in 2016. A late freeze in 2017 caused South Carolina to lose 85 to 90 percent of its peach crop. A total of 12,500 tons were reported for 2017.
Peach harvest in South Carolina is from May to September.
