Treatment for Canker on Trees and Ornamental Landscape Plants
Several different fungi that can cause cankers on trees and ornamental landscape plants. The fungus enters the plant through wounds or cracks on stems and trunks. Wounding often happens when there is damage to the soft, smooth bark either by mechanical injury, i.e. pruning and maintenance tools, or environmental stress to the plants. The most common injury to plants here in the desert southwest is by lack of water, sunburn or environmental stress to portions of the trunk or branches exposed to the hot afternoon sun. These stresses create cracks in the bark which are referred to as wounds. After the fungi spore enters the tree at a wound, the fungi kill the surrounding healthy tissue and expands in all directions, eventually cutting off the flow of nutrients and water to branches and twigs. Symptoms may start as a single branch dieback and leaf drop. Untreated, the fungi spores will continue to multiply during winter and spread through wind, rain, splash up, pollinators, and pruning tools in the spring.
Although there is no cure for the many known and unknown fungi, we do have a possible solution to help control the spread of some fungi by Basal Bark application of Monterey Garden Phos™ systemic fungicide with Pentra-Bark™ bark penetrating surfactant. The proper application of these two products show promise in controlling known fungal diseases and slowing the spread.
As per label instructions for the treatment of Fusarium subglutinans (pine pitch canker) common in conifers; “apply any time during active growth at a rate of 1 part Monterey Garden Phos™ to 2 Parts water PLUS 0.5 fl. oz of Pentra-Bark™ Bark Penetrating Surfactant in a hand held pump-type sprayer. Apply uniformly to 6-9 feet of trunk circumference. Spray from top down to ground level from either 1st branch or from as high as possible without exposing applicator to drift. Spray to saturation/runoff.” AVOIDING LEAVES.
*“Always read the label and do not exceed indicated application rates or apply more frequently than stated on label in order to avoid plant injury’”
Prior to any application, all dead and infected leaves, twigs, and branches must be cut and removed from the tree or shrub. Be diligent to clean pruning tools by spraying them with household 70%, or higher, Isopropyl rubbing alcohol, after each cut, to prevent manually spreading the disease. Clean up all surrounding litter and debris from infected plant and dispose of in bags and send to the landfill, eliminating the possibility for them to find their way into compost piles or wood mulch.
After treating, it is recommended to use a “tree paint” to seal and protect exposed bark from further damage. *see “tree paint” note. The use of “tree paint” is recommended as a preventative measure and could be applied during the winter months, prior to the spread of the fungi.
There are actions we can take to help the plant back to vigorous growth and vitality so it can fight against the expansion of the canker, giving the infected plant the opportunity to create a callous and “walling off” the infected area. Ensuring sufficient deep root irrigation, especially during June – September is essential. Proper plant placement, irrigation, and fertilizing practices are the only known preventative measures from canker development.
For more information regarding proper plant placement, irrigation and fertilizing practices contact Dr Q’s House Calls at HouseCalls@StarNursery.com or visit your local Star Nursery location and speak with our knowledgeable staff.
*Tree Paint note: Trunks may be protected by painting a 1:1 mixture of water and water-based indoor latex paint. One should never use acrylic or oil-based paint, which could harm or even kill the tree. There are commercial tree paints available, always read the label as some are “ready to use” and others need to be diluted with water.