OVERTON -- A Texas AgriLife Extension Service plant pathologist has begun evaluating new products, both chemical and biological, to control fireblight on peach and apple trees.
"Fireblight is a really big issue for commercial fruit producers of pears and apples, but also for homeowners and nursery growers who produce trees for homeowners," said Dr. Karl Steddom, plant pathologist.
Steddom is conducting the study at the Texas AgriLife Research and Extension Center at Overton where he is based.
Fireblight is the most devastating bacterial plant disease affecting apple and pear trees, according to Steddom.
The bacterium is usually introduced into the plant in the early spring as bees and other insects pollinate newly blooming flowers, he said.
Once introduced, the disease progresses very rapidly. The flowers soon start to rot and turn black, looking as if they've been burned by a torch.
"Hence the name fireblight," Steddom explained.
Within a week or two, the bacteria work their way down the flower stem into the new shoot via the tree's vascular system.
"As it works its way down, you'll start to lose leaves, and the whole shoot will die down to where it started its growth this year," he said.
Currently, there are only three products registered for use for fireblight on fruit trees.
"And we don't know (lacking independent tests), how well two of those products really work," Steddom said.
The tried-and-proven method, copper fungicide, involves spraying "pretty much every week" throughout the spring growing season, he said. The process is expensive and labor intensive for commercial growers, and more work than homeowners usually want or have time to do.
The treatment also leaves a bluish residue on plants that homeowners often object to, Steddom noted.
Copper fungicide isn't a restricted-use pesticide, which means homeowners won't need to have a Texas Department of Agriculture license to buy or use it, he said. However, it's not usually available in home and garden stores.
"And the trees don't end up looking that good, even with all that work," Steddom said. "So what we're doing is testing a number of old and new products to see how they perform."
For the test, Steddom inoculated 144 Kieffer trees with the fireblight bacterium. For the test, the container-grown trees were spaced 5 feet apart in a single row about 750 feet long. The single row allows him to control spray drift better from tree to tree than if he used a standard orchard arrangement,
he explained. This is important in order to limit a given spray treatment to a single tree.
Steddom is testing a total of 13 products, including copper fungicide and the other two registered chemical controls, plus ten products that are not yet commercially available. Some of the products are chemical controls; some biologicals. He is also comparing a relatively new class of pesticides called "biorationals," which, strictly speaking, are not biological, but are derived from biologicals.
"The biorationals are supposed to be effective and more environmentally friendly than chemicals, but we'll see," he said.
Currently, Steddom and AgriLife Extension don't recommend a frequent spray schedule for homeowners. Instead, the recommendation is to let the disease progress into the summer when days are warmer and drier.
"You want to wait until it's warmed up quite a bit, otherwise when you cut the shoot, the bacterial will get on your shears, and you'll transfer that bacteria from place to place," he said.
Shears may be sanitized after pruning one shoot before the next, but it generally takes a couple of minutes submerged in rubbing alcohol to kill the fireblight bacteria, according to Steddom.
Bleach can also be used, but it tends to cause shears to quickly rust.
"So an alternative is to use two pairs of shears," he said. "While you're trimming one shoot with one pair, the other pair can be sitting in the alcohol, disinfecting."
The one-year study was funded by the U.S. Department of Agriculture’s IR-4 Project, which is also referred to as the Minor Crop Pest Management Program. The full results will be available sometime in the fall of this year on the IR-4 website at http://ir4.rutgers.edu/ .
If some products show substantial or even partial control, IR-4 may fund the study a second year, Steddom added.
"It all depends upon what we learn this first year," he said.
Until the results of the study are known, growers or homeowners wanting more information about fireblight control in home orchards should contact their local county AgriLife Extension agent, he said.
A county-by-county directory of AgriLife Extension agents can be found at http://county-tx.tamu.edu/ .
"Fireblight is a really big issue for commercial fruit producers of pears and apples, but also for homeowners and nursery growers who produce trees for homeowners," said Dr. Karl Steddom, plant pathologist.
Steddom is conducting the study at the Texas AgriLife Research and Extension Center at Overton where he is based.
Fireblight is the most devastating bacterial plant disease affecting apple and pear trees, according to Steddom.
The bacterium is usually introduced into the plant in the early spring as bees and other insects pollinate newly blooming flowers, he said.
Once introduced, the disease progresses very rapidly. The flowers soon start to rot and turn black, looking as if they've been burned by a torch.
"Hence the name fireblight," Steddom explained.
Within a week or two, the bacteria work their way down the flower stem into the new shoot via the tree's vascular system.
"As it works its way down, you'll start to lose leaves, and the whole shoot will die down to where it started its growth this year," he said.
Currently, there are only three products registered for use for fireblight on fruit trees.
"And we don't know (lacking independent tests), how well two of those products really work," Steddom said.
The tried-and-proven method, copper fungicide, involves spraying "pretty much every week" throughout the spring growing season, he said. The process is expensive and labor intensive for commercial growers, and more work than homeowners usually want or have time to do.
The treatment also leaves a bluish residue on plants that homeowners often object to, Steddom noted.
Copper fungicide isn't a restricted-use pesticide, which means homeowners won't need to have a Texas Department of Agriculture license to buy or use it, he said. However, it's not usually available in home and garden stores.
"And the trees don't end up looking that good, even with all that work," Steddom said. "So what we're doing is testing a number of old and new products to see how they perform."
For the test, Steddom inoculated 144 Kieffer trees with the fireblight bacterium. For the test, the container-grown trees were spaced 5 feet apart in a single row about 750 feet long. The single row allows him to control spray drift better from tree to tree than if he used a standard orchard arrangement,
he explained. This is important in order to limit a given spray treatment to a single tree.
Steddom is testing a total of 13 products, including copper fungicide and the other two registered chemical controls, plus ten products that are not yet commercially available. Some of the products are chemical controls; some biologicals. He is also comparing a relatively new class of pesticides called "biorationals," which, strictly speaking, are not biological, but are derived from biologicals.
"The biorationals are supposed to be effective and more environmentally friendly than chemicals, but we'll see," he said.
Currently, Steddom and AgriLife Extension don't recommend a frequent spray schedule for homeowners. Instead, the recommendation is to let the disease progress into the summer when days are warmer and drier.
"You want to wait until it's warmed up quite a bit, otherwise when you cut the shoot, the bacterial will get on your shears, and you'll transfer that bacteria from place to place," he said.
Shears may be sanitized after pruning one shoot before the next, but it generally takes a couple of minutes submerged in rubbing alcohol to kill the fireblight bacteria, according to Steddom.
Bleach can also be used, but it tends to cause shears to quickly rust.
"So an alternative is to use two pairs of shears," he said. "While you're trimming one shoot with one pair, the other pair can be sitting in the alcohol, disinfecting."
The one-year study was funded by the U.S. Department of Agriculture’s IR-4 Project, which is also referred to as the Minor Crop Pest Management Program. The full results will be available sometime in the fall of this year on the IR-4 website at http://ir4.rutgers.edu/ .
If some products show substantial or even partial control, IR-4 may fund the study a second year, Steddom added.
"It all depends upon what we learn this first year," he said.
Until the results of the study are known, growers or homeowners wanting more information about fireblight control in home orchards should contact their local county AgriLife Extension agent, he said.
A county-by-county directory of AgriLife Extension agents can be found at http://county-tx.tamu.edu/ .
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