When it comes to treating trees and shrubs, Kyle Davis believes less is more.

“Most people overdo it and apply too much product,” says the chemical and fertilizer manager for Yellowstone Landscape, a $358 million, full-service company headquartered in Bunnell, Fla., that serves commercial and governmental clients. “A lot of plants are pretty hardy against insects and diseases. Contractors need to be smart about what they’re doing.”

Industry experts like Davis agree that understanding the basics of tree and shrub care is key to doing it right and avoiding some common mistakes. One such mistake occurs when contractors misidentify the affected plant, says Rob Gorden, director of urban forestry and business development for Arborjet.

“This sounds really simple, but you wouldn’t look at an oak tree and assume it’s going to get emerald ash borer,” Gorden says, adding that there are a number of books, apps and industry associations that can help contractors with plant identification.

Understand the stress

Once the plant is properly identified, contractors then need to determine what is causing it stress. Contractors should first consider environmental factors such as drought, improper planting or “volcano mulching” (when too much mulch is piled up around the base of the plant, cutting off water and nutrients to its root base).

“Thirty to 40 percent of problems in a landscape are actually not caused by insects or diseases. They are caused by environmental issues,” he says. “Contractors need to know how to identify what is wrong.”

Gorden also suggests contractors learn to identify the four or five most common pests and diseases in their area and then build upon that knowledge.

Kathy Glassey, plant health care director for Monster Tree Care, a $55 million tree care company with an 85 percent residential, 15 percent commercial clientele headquartered in Fort Washington, Pa., agrees that some companies are too quick to apply a pest or disease diagnosis without first identifying the environmental stressors. She warns that if the stress from environmental factors is not addressed, it can open the window for pests and diseases to take hold. But, if a pest or disease is in fact identified, contractors then need to select the right product and determine the proper treatment schedule.

“The timing of treatment is crucial to a successful application, and it requires proper planning,” Glassey says. “When there are pests and diseases, many times, companies will use a broad-spectrum product instead of a targeted product because they can’t get the timing right. This approach can impact beneficial insects and is not always best for the plant or for the environment.”

Get proactive

Rod Marquardt, national warm-season LCO accounts manager for Nufarm, agrees the use of the right product at the right time is important to get problems under control, and he adds that a proactive approach will generally give better results than a reactive approach.

“Most contractors do not take a proactive approach to tree and shrub care and rather wait until a problem is present,” Marquardt says. “But treating preventively for insects that come back around the same time every year can significantly improve the health of the plant and avoid last-minute 911 calls to take care of issues. Similarly, plant diseases are very hard to control curatively. Treating before an outbreak is the best way to take care of a disease.”

Marquardt says the type of product matters, too. For example, trying to control sucking or piercing insects with contact insecticides is often ineffective, he says, as pests like scale and mealybugs have an outer coating that is difficult for a contact product to penetrate. Using different types of products applied through various techniques also can maximize results.

“Using a horticultural oil, a systemic product and an insect growth regulator can provide excellent results when
one product alone may not do the job,” he says. “Different application techniques, such as root drenching, root injection, bark spray, bark banding, tree injection and foliar applications, can also affect efficacy.”