Decay in trees is bad, very bad. Unfortunately, existing fungicide products are not effective at stopping or reversing decay. Decay in trees is often unsightly, but it can also result in a safety or property damage hazard. Decayed trees, sooner or later, start shedding limbs or can topple in strong winds. Trees or large limbs riddled with rot can (and often do) land on houses, cars and, tragically, sometimes people.

Recognizing that, obviously you become informed about decay in trees and learn how to deal with it. There are two ways to deal with it, directly and indirectly. In most cases, it’s best to use both procedures.

Correcting co-dominant leaders early in a trees’ life can prevent problems with cracks. Photo: John Fech

Direct methods are procedures, activities and techniques that incorporate awareness of the existing level of decay and immediately discourage the advancement of the decay. They include corrective pruning, eliminating codominant leaders early in the tree’s life and removal of crossing, broken or diseased branches.

Placement of protective devices that reflect the harmful effects of winter sun will help to prevent further damage to the bark of sunscald-prone trees. The device should be white or beige in color, placed in such a way that it allows air to circulate around the trunk and can be easily removed in the spring. Thanksgiving to Easter is the best time to protect against further trunk damage from sunscald.

Using a resistograph to determine the extent of the internal decay. Photo: John Fech

Indirect methods include proper siting of trees (right plant, right place, right?); proper spacing; proper planting procedures to prevent damage to the bole from basal decay and root rot, as well as the promotion of a healthy root system; and mulching with coarse wood chips to prevent mower blight and reduce grass competition. Inexperienced mower operators can cause serious damage to the protective bark. This can occur acutely or chronically. Either way gives decay fungi the opportunity to invade the inner tree tissues. By starting the mulch application 3 inches away from the trunk and using a 2 to 3-inch depth, vigorous rooting is also likely to take place.

The selection of new trees for a landscape has a bearing on preventing future decay, as well. Certain trees, such as cottonwood and silver maple, tend to decay rapidly once infected. Other species, including walnut, Osage orange and ginkgo are more lignified and decay slowly. To make good choices, consult the botanic garden or extension office closest to your clients’ landscapes.

Tapping or “sounding” with the butt of a hatchet. Photo: John Fech

Above all, when it comes to decay prevention, do everything possible to protect the bark. A solid, uninterrupted bark layer is the first and best line of defense against the invasion of decay organisms.

Keep in mind that as trees mature, most of them acquire defects of one sort or another and that opportunistic decay organisms are ubiquitous. Due to differences in tree anatomy, physiology and reactions to stressors, decay may not be readily apparent. Tree decay can be present in significant volume without any external symptoms or telltale signs. On the other hand, cracks, rot pockets (portions of the trunk where large limbs have been removed), lightning strikes and fruiting structures are good indicators of internal decay. In other words, don’t rely upon superficial walk-by inspections to reveal rot in every tree. Sometimes you have to look more carefully.

Common inspection tools. Photo: John Fech

Remember, decay is a disease that often takes years to develop and become noticeable, unlike diseases that damage tree foliage. For this reason, older neighborhoods and landscapes are likely candidates for infected trees. Inform your customers in these neighborhoods, and especially those customers with mature trees, that you’ll be inspecting their trees for signs of decay and other problems.

Every arborist has his own way to inspect for decay and to calculate the extent or determine how much decay is present or, more importantly, how much punky soft wood exists compared to sound wood. For example, some tap the tree with the butt of a hatchet, using a resistograph or acoustic tomography and probe the tree with a sharpened piece of reinforcing bar. Obviously, the amount and extent of decay will determine which remedial options you should present to the property owner.