Covering Patch

Patch diseases are nasty, bothersome and costly turf marauders that create headaches regardless of where the course is located.

In fact, patch diseases are the most troublesome of the turf diseases because not only are they unsightly, but they can completely kill turf. And incidents may be on the rise.

“We have seen in many areas an increase in patch diseases,” says Dr. Jason Fausey, director, technical services T&O for Nufarm Americas. “In recent years, trends towards warmer temperatures with unpredictable dry weather, followed by heavy rainfalls have contributed to this increase. Each patch disease is unique and has a specific set of ideal environmental conditions that allow for it to thrive.”

Patch diseases are so destructive because the fungal pathogens infect the turf’s crown and root systems. “Without healthy roots and crowns the turf plants can be killed or function poorly, especially when placed under environmental stresses, such as summer heat in the case of cool-season greases,” says Dr. Joseph Rimelspach, program specialist in The Ohio State University Turfgrass Pathology Program. “In years where there has been increased stress on growing turfgrass, these diseases have increased.”

According to Rimelspach, this stress includes both very hot conditions for cool-season grasses in summer and periods of excessive rainfall and/or long periods of wet root zone conditions. “You may want to consider what areas of the country have different grasses (susceptible to different diseases) and what areas of the country experience stressful environmental conditions that could lead to more diseases,” he says. Regions with extreme weather may be more susceptible to patch diseases.

“This winter was mild in many locations, Fausey says. “Superintendents need to be cautious, as soil temperature and disease development were on the rise earlier than normal.”

Count on an appearance of summer patch and take-all patch every summer, but the severity of the summer will largely determine the level of turf damage, says Dr. Zac Reicher, technical specialist, Bayer Green Solutions Team. “Since it is a root-infecting disease, summer heat and drought stress will enhance the symptoms of summer patch on annual bluegrass, as well as take-all in creeping bentgrass,” he says. “Take-all also infects roots, but symptoms often diminish with summer temperatures because of reduced growth of the pathogen, only to reoccur in the early fall.”

Getting it under control

To successfully manage patch diseases, Rimelspach says it’s key for superintendents to maintain detailed records of past outbreaks with accurate diagnosis of the specific patch disease(s) they faced. “If you have had patch diseases, early pre-symptom applications of effective fungicides with proper placement are critical,” he says.

Soil temperatures often dictate application timing. For example, consider summer patch in Poa annua. Reimeplsach advises a first application of fungicide when soil temperatures are at 65 degrees, at a 2 to 3-inch depth, for two to three consecutive days. Apply the fungicide in a sufficient volume of water to move the product to the crowns and upper roots (this is assuming the fungicide is upward systemic, which most are that are used to treat patch diseases). In many cases, 4 to 5 gallons of water per 1,000 square feet is recommended. Light watering to move the product into the surface can be done before the product dries. But, often irrigation systems deliver uneven amounts of water, and it is not wise to dilute fungicide to the point of an ineffective rate.

Curative measures depend on how far the disease has progressed in the plant if such steps will bear fruit… so to speak, says Dr. Joseph Vargas, a professor in the Michigan State University Department of Plant, Soil and Microbial Sciences.

“If it has already entered the crown of the plant, it is too late,” Vargas says. “But, on the other hand, if you catch it early enough, or if the crowns of all the plants have not been infected, curative fungicide applications can prevent further damage.”

The only way to stay ahead of patch diseases is to follow preventative programs outlined by regional turfgrass pathologist or extension specialist, says Dr. James Kerns, an assistant professor and extension specialist of turfgrass pathology at North Carolina State University.

Kerns recommends monitoring soil temperatures (at a 2-inch depth) and make the initial fungicide applications when the temperatures are consistently (four or five days) at certain temperatures (take-all patch in cool-season turf between 55 and 65 degrees, summer patch 65 degrees and above, spring dead spot 70 degrees in autumn, take-all rot in warm season grasses 75 degrees or higher). “For example, for take-all patch of creeping bentgrass the first application should occur when soil temperatures reach 55 degrees for four or five consecutive days,” Kerns says. “A second application 28 days apart should be sufficient unless soil temperatures remain below 65 degrees after the second application.”

Summer patch is now better understood and two well-placed fungicide applications 28 days apart starting when 2-inch soil temperatures average 65 degrees are usually effective. Says Reicher, “Most effective products tend to be the DMI fungicides (Bayleton, Tartan, Mirage, Banner, etc.), and a third application may be justified on areas with a history of damage.” Control of take-all can be effective with DMI or QoI fungicides, but timing is earlier in the spring when average soil temperatures are 55 degrees-plus, with a second application three to four weeks later, and a fall application when average soil temperatures return to 45 to 60 degrees. Since fungicides need to be soil-applied to be effective, apply in 2 to 5 gallons water per 1,000 square feet and water in with 0.1-inch of water immediately after application.

Recovery

Recovery is typically slow because injury has occurred during warm weather. “Fungicides, such as azoxystrobin and thiophanate-methyl, can be curatively applied, but need to be watered in to the turf profile,” Vargas says. “The DMI chemistry can be effective in managing the patch diseases preventively, but, because of their PGR effects, should not be used curatively. It is also important to foliar feed the infected plants nutrition to help them recover, since the root systems have been severely damage.”

Adequate and proper fertilization is essential for healthy turf and a must to manage and hopefully prevent these diseases, Rimelspach says. Timing is also important, so that growth is promoted at the proper time for the turf species. In addition, “minor elements” need to be monitored, especially for some patch diseases.

“An example is that take-all patch is greatly increased if there is a deficiency in manganese,” Rimelspach says. “Make sure you have a good working relationship with a reputable soil testing lab and/or consultant.”

Fausey adds proper nutrient management along with pH balance, fertilizer type and timing all become very important when managing patch diseases, especially in “trouble areas” where these disease have occurred in the past.

Soil nutrients can certainly impact patch diseases. “Avoiding high nitrogen fertilization is important when conditions favor brown patch,” Silcox says. “Low nitrogen fertility will favor brown ring patch damage. Large patch of zoysiagrass may be enhanced by nitrogen applications during September or in the spring when the disease is active. Summer patch can be enhanced by nitrate-based fertilizers, so acidifying fertilizers should be used as nitrogen sources.” Nitrate-based fertilizers may also enhance take-all patch and adequate levels of potash and phosphate will help minimize this disease. Fall applications of nitrogen should help turf outgrow symptoms of yellow patch the following spring.

Don’t fall behind

Patch diseases are extremely visible and sometimes destructive, so extreme responses typically happen when these diseases develop, Kerns says. It is best to make sure the disease is diagnosed and work systematically to alleviate the damage. “A reactive approach with these diseases can result in further damage and result is wasted applications,” he says. “The key is to work with your local turfgrass faculty to help you with these diseases.”

Dr. Rimelspach sums up the situation, “Have an accurate diagnosis of problems. Stay ahead of the game. Once you see symptoms you are behind. If the summer is long and brutal, additional applications will be needed to protect the turf and minimize infection. Have a good plan in place and adjust depending upon weather conditions and the performance of the turfgrass.”

Vigilant monitoring, good record keeping to fall back upon, consultation from diagnostic professionals, feeding your soil to insure its health and resistance capabilities, and a well-thought-out and effective plan to quickly put in place if problems occur are vital to keeping your turfgrass free of patch diseases this year and in the future.

John Torsiello is a turf writer based in Torrington, Conn., and is a frequent GCI contributor.