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Leaf Spot – Don’t Let It Ruin Your Landscape

When we think of lawn care, we think of our grass but the trees and shrubs around our house are what gives us privacy, color and curb appeal. Too often our shrubs are left to fend for themselves which can in turn lead to some major problems. And let's be honest, purchasing trees and shrubs isn't cheap, so think of caring for your trees and shrubs as an investment.

There are a variety of threats to trees and shrubs. Have you heard of leaf spot? Even if not, we bet you've seen it. We're going to share information about what leaf spot is, how it develops and ways to avoid it.

About Leaf Spot

Leaf spot is a common descriptive term applied to a number of diseases affecting the foliage of ornamentals and shade trees. The fungal and bacterial agents that cause leaf diseases often exist naturally in the air and soil. Since it's in the air and in the soil, it can occur on many types of plants, including indoor and outdoor shrubs and trees but is most commonly found on hollies, Indian hawthorns and hydrangeas.

In some cases, the center of the leaf will dry up and fall out, giving the leaf a "shot hole" appearance. Here's the thing, there are three critical factors or conditions that must exist for disease to occur:

  • Susceptible host
  • Pathogen
  • Right combination of poor environmental conditions

The relationship of these factors is called the disease triangle. Without all three, the disease cannot survive. Keep reading to learn more.

Causes of Leaf Spot

Warm nights combined with high humidity provide an ideal environment for disease development. Optimum daytime temperatures for leaf spot are 77° to 95°F with night temperatures above 61°F and a relative humidity of 90 to 95%. That's a pretty classic late spring to early summer normal here in the southeast. With that being said, shady protected areas that may not get good airflow, and thereby being humid, are often where leaf spot will make its appearance. Because the pathogens that cause leaf spots are blown around by the wind or splashed by rain or irrigation, a leaf spot infestation can potentially arise anytime. When inspecting your shrubs, check the inside lower area of the bush as that is where you have the highest humidity and most shade-again, ideal conditions for leaf spot.

What It Looks Like

Leaf spot can vary in size depending on the plant affected. The color can vary from red, purplish-brown, tan or black. The discolored areas on the leaves is the actual fungus itself. If left untreated, it can cause almost full discoloration and make the plant drop its leaves, sometimes permanently. Generally speaking, although leaf spot disease can easily spread, it will not seriously harm the plant.

Treating Leaf Spot

This eye-sore disease can live all winter in dropped leaves so it's important to clean up and remove any infected leaves. But act fast because leaf spot can mature in as little as two weeks. Raking up and disposing of infected leaves as they drop and pruning out dead twigs can help control the disease by removing spores that can re-infect the new leaves. This will not cure the problem but it can help minimize infections.

For plants that chronically are plagued by leaf spot, gardeners find it more convenient to replace a plant with a different species or a variety that is more resistant or tolerant of disease.

At Turf Masters, our Tree & Shrub Care program focuses on fertilization as well as preventative and curative insect and disease control throughout the year. During your seasonal property inspections, we'll share recommendations on how to enhance the health and beauty of your landscape. As with most shrub and tree diseases, the quicker you can diagnose, the quicker you can treat.

Contact us for your free landscape evaluation today.