Mar 30, 2012

Painting tree trunks protects against rodents, borers

Painting fruit tree trunks with white latex paint can prevent the bark from splitting and cracking off. Splitting can happen when the tree is exposed to freezing evening temperatures, followed by a daytime thawing. The painted white trunk will help reflect sunlight during the daytime hours and keep the tree warmer at night, according to a University of Missouri Extension website.

Painting is also one of the ways growers can protect their trees from rodent damage. In northern climates, mice and voles can girdle a tree under the snow cover. Rabbit damage can also be prevented by adding a rabbit repellant to the paint mixture, according to a report from the University of Vermont.

On the Virtual Orchard Internet listserv, several growers recently discussed other effects they have noticed from painting tree trunks.

“I have noticed a very surprising and useful side effect of painting the lower tree trunks in my orchards with undiluted white latex paint,” said Randy Steffens of Shepherd’s Valley Orchards, Chattanooga, Tenn. “I have found this practice completely eliminates damage caused by rabbits chewing on the trunks, and I haven’t had to add anything. I’m not sure why this works (perhaps the rabbits in Tennessee are not as voracious as elsewhere), but for me, it is absolutely stunning how effective it is.”

At Shepherd’s Valley, the use of paint has made rabbit guards obsolete, Steffens said. He even painted after the rabbits started eating the bark in the fall. A white, latex-paint application completely eliminates the problem for him, he said.

“Usually, the rabbits take a bite or two of a few painted trees and then leave them alone for the rest of the season,” he said. “These results have been predictably occurring for a few years now, ever since I started the practice of painting my trunks.”

It isn’t just mice, voles and rabbits that the practice helps. Boring insects have taken a dislike to the practice too, said Kevin Hauser of Kuffel Creek Apple Nursery, Riverside, Calif.

“If it works again this year, I’m ready to declare victory, as we’ve gotten hammered from borers over the last several years,” Hauser said. “We’ve settled on one-third white paint (I use Glidden Gripper paint), one-third all-purpose drywell joint compound and one-third water. This brushes on well, but makes a thick coat.”

Hauser credited John Bunker of Fedco Trees in Maine for originally using drywall joint compound.

“They use it to prevent winter sunscald, and I used it initially to prevent summer sunburn,” Hauser said.

A study by David Kain and Art Agnello at Cornell University backs up the claim about borer activity.

“In a previous study, we had applied a 50:50 mixture of water and white latex paint using a sprayer,” Kain said. “While spraying paint on was efficient, it was not effective at the 50:50 rate in preventing dogwood borer infestation. In this study, we applied the paint at full strength with a paintbrush. While this took considerably more time than spraying, it was effective and long lasting.”

According to the study, in a few instances burrknot tissue grew through the paint layer and became unprotected, opening the door for tissue damage and infestation issues, Kain said.

By Derrek Sigler, Assistant Editor