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Disease In The Trees

For many homeowners, landscaping means more than just plants. For those who consider themselves gardening enthusiasts, it can be a relaxing and—as studies have shown—even healthy pastime. Indeed, many invest plenty of precious time and money on getting just the right look for their home’s exterior décor. That’s why when plants in a garden are found to be diseased, it can be more than a minor irritation. Sometimes the fix can be as simple as a little extra attention—an extra feeding, pruning, or a little more time soaking in some sun. But what happens when a plant begins to show symptoms that you’ve never seen, and it doesn’t seem to respond to any type of treatment? We encountered this recently when one of our customers contacted us regarding a strange growth he found on one of his mature ligustrum shrubs. The brown, irregularly-shaped growth appeared almost mold-like, but upon closer inspection it was found to be a cluster of stunted plant growth, and its spread began to result in several bare spots. Though similar symptoms have been observed as a result of bacterial infections, our field expert recognized that this was no ordinary disease and took a sample to the Florida Agricultural Center for more information, and it turns out we’re not alone in our concern. 

According to UF Extension Director Dr. Juanita Popenoe, similar reports have been received from as far south as Miami, and now the problem seems to be hitting closer to home. We also spoke with Dr. Phil Harmon, Associate Professor of Plant Pathology at the University of Florida, who has been assisting in the research on this new pathogen.​ According to Harmon, although no conclusive evidence has been reached, there is some indication that the culprit may be a disease-causing pathogen known as a phytoplasma. These microorganisms are similar to bacteria and infect plants via insect hosts. “Once it’s infected, symptoms may come and go”, says Harmon. “Some plants will show very mild symptoms for many years, so we certainly wouldn’t say we need to pull out all these plants and start over. But at the same time, there’s nothing we could recommend to cure a plant that is already affected.” But while that synopsis doesn’t sound overly optimistic, Dr. Harmon added that “the severity of the symptoms is dependent upon environmental factors such as where they’re planted, how much stress they’re under, and how they’re managed,” which gives us some hope that a healthier shrub may be better suited to handle any such infection. “Because it’s something new,” he says, “we just don’t have all the answers right now. We’re working on it, but we’re a long way away.”

As for Deans, we’ll continue to seek new ways to combat this disease through continued communication with university extensions and will relay any details to our readers as they become known. In the meantime, it never hurts to ensure your prized landscaping is kept healthy with a regular routine of feedings and pest prevention. If you’re interested in learning more about our lawn or shrub program, feel free to call (352) 787-5300