Plant disease control possible through tree pruning

Wednesday, January 17, 2018

Homeowners and landowners looking over their property should take quick action if their trees and shrubs are observed to have wilted branches or dieback.

“It is important to closely monitor landscape trees and shrubs for symptoms of disease,” said Robert Bourne, Bryan County Extension director and agricultural educator. “Quick action can possibly save the plant.”

Diseased limbs should be pruned at least 10 inches from the dieback and into healthy wood, according to recommendations from Oklahoma State University’s Division of Agricultural Sciences and Natural Resources, of which the Oklahoma Cooperative Extension Service is a part.

“With fast-spreading diseases such as fire blight, it is better to prune 12 to 18 inches below the discolored sites,” Bourne said. “If the symptoms have reached the main trunk, it may not be possible to save the plant.”

When pruning, it is best to prune plants when it is dry and when weather is expected to be dry for the next three or four days. Bourne reminds landscape managers that sanitation is critical for preventing the spread of plant diseases.

“If pruning is done with handheld tools, they should be sanitized between cuts,” he said. “Common disinfectants including Lysol, rubbing alcohol, disinfecting wipes or a 10 percent solution of household bleach are all good choices for cleaning the blades. If using a chainsaw, it is not necessary to clean the tool between cuts.”

Diseased plant material should never be incorporated into the compost pile. It should always be discarded with regular household waste.

“It is difficult to reach and maintain temperatures required to breakdown pathogen propagules so many pathogens can survive the composting process,” Bourne said. “Do not put diseased plant material out with green waste. In many cities, the green waste is used to make compost that is utilized by the city and occasionally made free to home gardeners.”

Once the tree or shrub has been pruned, continue to monitor it for additional symptoms. If diseased branches appear, remove them by pruning. Bourne said it can often take several years to “clean-up” a diseased plant.

“If the plant gets to the point that it is no longer aesthetically pleasing, has become hazardous or the main trunk has become diseased, the tree should be removed,” he said. “Depending on the size of the tree, you may need to hire an arborist.”

Additional information is available through all OSU Cooperative Extension county offices, typically listed under “County Government” in local directories.