SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: https://read.dmtmag.com/i/162108
FieldScience year after year, numerous fungicides from the strobilurin or DMI class of fungicides can easily provide 21-28 days of rust control. 3. NECROTIC RING SPOT As a root-infecting fungus, this (Ophiosphaerella korrae) is one of the more frustrating diseases an sports turf manager can face because once symptoms appear it's too late to treat for the fungus. Adding to the frustration, fungicide applications are notoriously ineffective for this disease because the timing of application is critical and the fungicide also must be watered into the rootzone to the point of infection…and it's darned hard to water a fungicide through 2 inches of grass and a half inch of thatch. The necrotic ring spot fungus is only active on turf roots when soil temperatures are roughly between 55 and 65°F, which is usually mid to late spring. But the circular frog-eye patches characteristic of the disease (Figure 4) often don't appear until early summer, after the fungus has gone into dormancy. Figure 5: IF YOU SEE white mycelium following hot, humid weather in the summer don't automatically assume it's Pythium blight…it may be brown patch. unchecked. Symptoms appear as diffuse patches of slightly brown or even purple-colored turf, and in active infections white mycelium can be present in the turf canopy (Figure 5). Fungicide applications are an effective means for controlling brown patch, especially Prostar or those from the strobilurin class. However, limiting nitrogen fertilization and irrigation during hot periods can significantly suppress the disease in the absence of fungicides. However, if you manage tall fescue or experience prolonged periods of hot and wet summer weather, fungicides may be required for effective brown patch control. 1. Figure 4: NECROTIC RING SPOT can be devastating on recentlysodded turf, something quite common on athletic fields. SUMMER PATCH This root-infecting disease (Magnaporthe poae) is similar to, and often confused with, necrotic ring spot but has a few key differences. Like necrotic ring spot, summer patch is a root-infecting fungus that primarily impacts Kentucky bluegrass (though ryegrass and fine fescues can also be impacted). Like necrotic ring spot, At this point, all you can do is manage or 'baby' the turf and its weakened root system the best you can through more frequent irrigation and fertilization. If you repeatedly observe this disease on your field, implement any healthy rooting practices you can think of to increase the number of healthy roots and help the plant ward off symptoms. In addition, use acidifying fertilizers or other acidifying amendments because the disease is more severe when soil pH is above 7.2. Since excessive thatch layers can harbor the fungus, work to minimize the thatch layer to one half inch of thickness or less. As a last resort, some granular fungicides may be able to provide suppression if applied at the proper soil temperature and watered in. 2. BROWN PATCH If you manage a field with a significant amount of tall fescue, you likely know all about brown patch (Rhizoctonia solani). This foliar fungus requires prolonged periods of hot, humid weather to cause disease and can ravage tall fescue plants if left 22 SportsTurf | September 2013 Figure 6: OFTEN similar in appearance to necrotic ring spot, summer patch can be destructive even on high-end athletic fields because of the inability to detect its presence until the damage has been done. www.sportsturfonline.com