Tree & shrub care—insect management

Here are the biggest “faux-pas”:

• Lawn irrigation hitting the tree & shrub foliage. This is often the sole cause of serious disease infestation.  Foliage is not meant to be wet all of the time. Foliage that gets wet every time we water the lawn will be more susceptible to fungal diseases and, in some cases, to insect infestation. Trees and shrubs, once well established, normally require very little water. When they do, they should be irrigated with a trickle of water at the base so that only the roots are getting watered.

• Improper planting. OK, so you just dropped $500 on a nice specimen tree. It comes with a root ball, surrounded by wire mesh. You dig a hole and drop it into the ground. It looks good for the first few years but, in 5 years, you wonder why the tree is struggling. Most likely, the answer is a girdling root. Unfortunately, this situation is not easily remedied and often results in the need to remove the plant. Please be sure that any new planting has the wire mesh or burlap removed and the roots loosened from the root ball. Many times, the roots have been in the ball for quite a while.  If they maintain that position, even after the wire mesh is removed, the roots will continue to grow in a circle, right around the tree/shrub, and eventually will strangle the trunk. This being a major root, and mostly underground, removing it is difficult, and it removes a major portion of the root system. Therefore the most economical choice is to remove it. UGH!

• Putting a plant in the wrong place.  Putting a shade-loving rhododendron out in sunny area will cause it to weaken and will become more susceptible to insects and diseases. Please do a little homework on plantings before you just plop them into the ground.

• Planting grass right up to the base. Trees & shrubs and grass don’t naturally go together.  Therefore there’s no reason to plant grass under a tree canopy and expect both tree and grass to thrive. It is best to create a mulch bed that extends out to the drip edge of the tree or shrub. That way, there’s no competition for nutrients and water and both tree and lawn will be healthier for it.

• Weed whacking around the base of a tree or shrub. Keep the power tools away from the bark! A sure-fire way to kill a young plant is to run that bad boy right around it and cut into the bark. What looks like “just a scratch” to you, can be fatal to your tree or shrub. Just another reason to give plants a good mulch bed and keep the grass away.

• Piling mulch on year after year.  About 2" of mulch is all there should be over the soil surface.  What we often see is mulch being added either before the old mulch has had a chance to decompose or without removing it. As a result, mulch often “climbs” up the tree or shrub trunk.  The trunk is not meant to be subterranean. It needs free flow of air around it to breathe.  

• Planting too close together. That cute little tree and shrub may grow into an overcrowding monster! This is especially true for foundation plantings. Foundation plantings are there to hide the concrete foundation. They’re usually very small when they’re installed but, without regular pruning and maintenance, they can become overgrown. This crowded condition, plus the shelter of the house, can create a perfect environment for insects and diseases, not to mention fierce competition among plants. These plants often become so deformed from growing through, and around, each other that they can’t be saved by severe pruning and must be removed.

• Pruning them “just to look nice.”  Most ornamental plantings have a natural shape that should be maintained throughout their lives. Pruning should be done properly to best maintain that shape and control the size. If you want to make an arborvitae shrub look like Mickey Mouse, then good luck with that. (It’s natural shape is more like Patrick Star…).  But seriously, plants that are deformed by pruning are weaker, and more susceptible to problems.

• Improper pruning.  Making the wrong pruning cuts, at the wrong time of year, and taking off too much live crown can weaken the plant. The pruning cuts can be entry points for both insects and diseases. Also, improper pruning cuts may never properly heal. This will make them look ugly and provide entry points for decay, in addition to insects and diseases.

With a little planning and forethought, these “faux-pas” can be avoided. You should stay ahead of your plantings so that they don’t get too big. While they don’t need weekly mowing, an annual maintenance pruning is the healthiest way for you to control their size, form, and vigor. A healthy plant is the best defense against disease and insects. Let us help you develop a plan for your trees and shrubs.

Here are a few of the more common insects that are affecting landscapes in our area.