How to Deal with Insects & Disease

By Katie Neis

Insects and diseases can affect your new trees at any time, especially when they’re young. Friends of Trees chooses trees based on their disease and pest resistance, but sometimes nature gets a little unruly and throws her best curve ball at us.

With proper diagnosis, maintenance and—in some cases—treatment of your new tree, we all can live long healthy lives in harmony.

Stress

Minimize it.

Trees deal with environmental stresses, such as shading and competition for water and nutrients by adjusting their growth and development patterns based on the availability of the resources. Always keep your tree mulched, hand weed near the trunk, water diligently through the establishment period (first three summers) and during  dry spells, and NEVER scrape the bark off the tree with lawn tools. Pathogens and insects can enter a tree through damage in the bark. If you do get bark damage, mulch heavily and keep up the watering to bolster the trees “immune system.” If the bark damage is severe (more than 1/3 of the tree’s diameter), the tree could potentially be hazardous, so call an arborist.

Almost always, the stress a tree experiences is much, much greater in an urban environment than in a forest.

Insects

Some insects can cause injury and damage to trees. In many cases, however, the insect problem is secondary to problems brought on by a stress disorder or pathogen.

Know exactly who your little insect friend is. Keep in mind that most insects are beneficial rather than destructive. They help with pollination or act as predators of more harmful species. Therefore, killing all insects without regard to their species and function can actually be detrimental to your tree health.

Diagnosis

You can take a leaf or insect sample to your local nursery, call your local extension service, or hire an International Society of Arboriculture-certified arborist to take a look at the tree.