Total Landscape Care Digital Magazine
Issue link: http://read.dmtmag.com/i/132471
PEST MONTH Anthracnose and Apple Scab of the Dogwood Anthracnose S howers not only bring flowers, but they also boost the likelihood of anthracnose and apple scab outbreaks, points out plant pathologist Karen Rane. "The diseases are favored by leaf wetness, so spring rainfall helps promote infection," says Rane, director of the University of Maryland's Plant Diagnostic Laboratory. "They're common, chronic problems, and their incidence a lot of times depends on the weather, the cooler and wet spring weather in particular. Some years those diseases are bad, some years they are less serious, but they're usually around to some extent every single year." Anthracnose is a term covering a large range of plant diseases characterized by small areas of dead tissue or cankers caused by fungi. Each tree species has its own anthracnose-causing fungus – they do not cross-infect – but the results are common. For popular shade trees such as oak, sycamore and ash, the signs range from the small dead spots on the leaves to premature defoliation, twig death, and bud killing resembling frost damage, according to the industry-respected Penn State University Extension resources compiled and updated by Gary W. Moorman, Professor of Plant Pathology. For apple scab, a fungal disease specific to apples and crabapples characterized by dull black or greybrown lesions, "there can be reinfections all through the growing season, so if there's rainfall during the rest of the summer, you can have a series of infection periods and have a buildup of disease," says Rane. "Anthracnose tends to be a spring problem; you don't see it building up over time that much across the entire growing season like you can with the scab." The inseason recurrence of apple scab is not unique among plant diseases, but it does make it different from anthracnose, says Rane. The first choice and the easiest way for tree care professionals to manage apple scab is to help customers select trees that bear crabapple varieties resistant to the disease. Older cultivars more likely to have recurring apple scab require fungicide application when the buds break in the spring, and then again according to particular label directions, at least one or two more times until the leaves emerge. "Common anthracnose can often be tolerated without treatment. Most of the popular shade trees will just produce more leaves, and in the middle of the summer you'd never know they had anthracnose, or you just wouldn't see it. They refoliate and it's no big deal," Rane says. "The exception is for dogwood anthracnose, which can actually kill dogwood trees. Not only does it cause spots on leaves, it causes twig dieback, and eventually those twigs can die back to the trunk and give you a canker on the trunk. When you have several cankers on a trunk, it can girdle and kill the entire tree." For high-value dogwood trees, preventive fungicides similar in application to those for apple scab are recommended. Defoliation by Apple Scab Photo credit: Valent Professional Products. Tourney® Fungicide: Outstanding Control of Anthracnose and Apple Scab T ourney® Fungicide from Valent Professional Products provides excellent control of a broad spectrum of diseases affecting outdoor woody ornamental plants in landscape settings, including anthracnose, apple scab, leaf spots, powdery mildew, rusts and Rhizoctonia root and crown rot— all with just one product. Apple scab can be an especially PestoftheMonth_TLC0613_PG.indd 44 tough disease to control, but thirdparty trials show that Tourney delivers best-in-class control even on 28-day spray intervals. A very active fungicide even at low use rates, Tourney is an important tool for preventive disease control programs. There's no need to purchase and apply multiple fungicides when Tourney can do the job alone, saving you time and money in the process. Tourney is also available as a foliar spray or soil drench for root and crown diseases, providing lawn care operators with valuable application flexibility. For more information on Tourney, visit www.valentpro.com/tourney or contact your local Valent territory manager. Information sponsored by Valent Professional Products 5/21/13 3:34 PM