The low-down on disease

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November 15, 2016 -  By

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Spring’s warm, moist weather is the perfect breeding ground for turf and ornamental diseases, so lawn care operators should be proactive to keep problems at bay.

Spring’s warm, moist weather is the perfect breeding ground for the fungal spores that cause most turf and ornamental diseases. From curled, spotted leaves, to discolored patches of turf, diseases in the lawn and landscape are not only unsightly, but can also cause damage to surrounding plants. It’s important for lawn care operators to be proactive in order to keep diseases and infestations at bay.

Drew Zwart

Drew Zwart

“Most diseases are going to occur in the spring because the vast majority are caused by fungi related to spring’s moist weather,” said Drew Zwart, a plant pathologist for Bartlett Tree Experts in San Rafael, Calif. “When leaves first emerge they are the most tender and susceptible to pathogens, so this is a good time for LCOs to be scouting.”

While Nicole Ward Gauthier agrees that most diseases occur in the spring when plants break their dormancy, the extension plant pathologist at the University of Kentucky in Lexington says LCOs shouldn’t necessarily wait until spring to begin scouting for disease. Instead they should be constantly monitoring their customer’s lawns and landscapes for signs of infection, and try to control these infections before disease takes hold. She suggests focusing on the previous year’s diseases and analyzing how those pathogens will overwinter to get an idea of the coming year’s risk.

Nicole Ward Gauthier

Nicole Ward Gauthier

“Once you’re scouting and see disease, infection has already occurred,” she said. “Symptoms of disease can occur days, weeks, even months after infection, so we don’t focus as much on scouting as we do on looking at risk.”

Rick Miller, senior sales representative for Dow AgroSciences in Folsom, Calif., says common diseases often occur in susceptible plants at the same time each year, so it’s a good idea for LCOs to keep detailed records of their properties so they know what to expect. Available tools such as university disease forecasters can also help LCOs predict impending issues for some diseases. Because plant diseases vary regionally, Miller stresses the importance for LCOs to have strong relationships with their local university and extension services.

“Sometimes you scout and maybe you’re not sure what something is, so you’ll have to get it identified,” he said. “There are experts, test kits, and university resources that can be utilized.”

One of the most common issues in the landscape is root disease, caused by a specific group of root pathogens called phytophora. This can be a result of improper planting techniques, planting in compacted soils with poor drainage, overwatering, and lack of sunlight.

“It would be very difficult to find a landscape that didn’t have at least a few plants susceptible to root disease anywhere in the country,” Zwart said. “There are many species of phytophora and it runs the gamut of the type of plants it can affect.”

Other common ornamental disease include types of blights, cankers, rusts and wilts, as well as foliar leaf spots, blackspot, scabs and powdery mildew. Some common turf diseases include brown patch, dog spot, dollar spot, leaf spot, rust and fairy ring. While disease can affect virtually any plant, some are more susceptible than others. Plants in the rose family, which include ornamental fruit trees like apples, cherries and pears, are highly susceptible to both disease and insect infestations. Plants such as crepe myrtle trees, types of azaleas and plants and turf that are not native to their areas are also more likely to be impacted by disease.

bartlett tree

 

There are several cultural control methods LCOs can utilize to minimize turf and ornamental diseases. One is sanitation, which involves removing diseased tissue from the plant source. Practices such as raking up last year’s diseased leaves, pruning back dead branches, and removing rotted or diseased fruit from trees are ways to remove the spores that cause fungal diseases. Another cultural control method is making sure plants are properly spaced, which improves the plants’ air circulation and helps reduce stress.

Rick Miller

Rick Miller

Other cultural control efforts include applying fresh mulch to the landscape to help protect and nourish the soil, mowing turf at the appropriate height with a sharp blade, and applying the correct amounts of water and fertilizer. Miller says that proper pruning practices are important to prevent disease in many fast-growing ornamentals, adding that vertical cuts will accumulate less moisture than horizontal cuts, providing less potential for fungal disease at the wound sites. He also discourages the use of overhead sprinklers to water the landscape in susceptible ornamentals such as roses.

“Oftentimes the spores that cause disease are splashed onto the plant,” Miller explains. “By moving to microsprinklers or drip irrigation, you minimize splashing of fungal spores onto the ornamentals, reducing disease outbreaks.”

In terms of chemical control methods, fungicides are used to suppress turf and ornamental diseases. Zwart stresses the importance of choosing a fungicide based on the specific pathogen that needs to be controlled. He adds that it’s important to rotate products to avoid resistance, and says that fungicides always work better preventatively than after the disease has taken hold. Experts agree that cultural practices should be combined with fungicides to achieve the best results.

“If you’re not going to use the cultural practices, then don’t use the fungicide,” Ward Gauthier said. “They have to go hand in hand.”

Emily Schappacher

About the Author:

Emily Schappacher is a freelance writer based in Cleveland.

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