Recent reports from western Canada indicate Microdochium (fusarium) patch to be active and aggressive. With cooler conditions rolling into the east as of late, a few cases of early fall fusarium have also been reported in the Eastern provinces as well. With what could be a rainy couple months ahead of us, staying on top of disease will allow you to best prepare your golf course for the long winter and snow mould pressure that is inevitably mounting.
Optimal conditions that favour disease outbreaks range from 8° C to 20° C with high relative humidity (>80%) for more than 24 hours. The Pacific Northwest and Atlantic Canada can be the ideal climate for Microdochium patch given the long dew periods, frequent rainfall, and cool, wet weather that persists for much of the growing season. Without snow cover, Microdochium patch occurs as reddish-brown to copper-coloured spots in the turf. The spots range in diameter from less than 2.5 cm to about 20 cm, but larger spots are sometimes found. The pathogen is a prolific spore producer and can spread quite readily via mechanical traffic, surface water, and even wind. Mycelium and spores survive in the thatch and debris of the turf stand and re-infect when conditions are favourable and turf growth is slow. This disease is favoured in shaded or poorly-drained locations and in areas that receive excessive nitrogen fertility.
Balanced fertility is a key aspect of managing Microdochium patch. Nitrogen fertilization that encourages lush growth into the late fall will make the turf more susceptible to M. patch throughout the winter. Lowering the pH of the turfgrass environment has shown to hinder the growth and development of M. patch, however, these practices must be met with some level of caution, as frequent sulfur applications can lead to other agronomic problems such as black layer and elevated anthracnose pressure during summer months.
Cultural practices that reduce leaf wetness duration such as dew whipping and especially rolling are known to contribute to disease reduction. Recent research has also shown frequent applications of phosphite fungicides are quite effective in limiting disease, especially when coupled with low amounts of sulfur to reduce soil pH. All of these factors combined are important strategies that are often required in combination with a sound fungicide plan, particularly in areas like the Pacific Northwest, where the disease must be managed with a programmatic approach.
Due to the persistent nature of the pathogen and the long-lasting conditions that favour epidemics in parts of Canada, chemical options are often necessary to achieve adequate control. “Contact” fungicides like chlorothalonil and iprodione (local penetrant) can be very effective components in a management regime when snow cover is absent. If there is persistent snow cover for three months or more, systemic fungicides must be used to achieve adequate control. Many chemical options are available from a variety of different manufactures. The chemical classes that have shown to deliver the best control of Microdochium patch, especially when used in combination or as rotational components within a program include the benzimidazole, DMI, dicarboxamide, nitrile, and QoI chemistries.
As with all diseases, an integrated approach for preventive management is always best. Interface Stressgard and Trilogy Stressgard are two great options to consider as tools in managing Microdochium patch this season.
Image 1. Characteristic Microdochium patch symptoms of copper-coloured spots and signs of fluffy pink mycelia visible in dew-soaked morning conditions. Photo – Paul Giordano, Bayer CropScience.
Image 2. Damage associated with Microdochium patch infection on an annual bluegrass putting green. Note the tan spots with copper/pink margins. Photo – Rob Golembiewski, Bayer CropScience