The UMass Plant Diagnostic Lab has been struggling over a number of cases of bentgrass thinning and dying. In most cases, no plant pathogenic fungi have been noted in the foliage, crown or roots. In some cases, ectotrophic root-infecting fungi, consistent with the take-all fungus, have been noted but not in significant amounts. Superintendents have had a broad spectrum of fungicide coverage with little if any response by the turf. It is likely that environmental conditions and/or cultural practices are playing a primary role. A syndrome referred to as Bentgrass Decline, largely the result of high temperatures has been written about for several years.
Pythium blight has been noted on several golf courses, and occurred in S. Deerfield during the very first heat wave. This disease does not usually occur until the hot humid days of July and August. However, its here now and will return whenever conditions are favorable (hot and humid days, with warm nights). Chloroneb, etridiazole, mefanoxam and fosetyl-al are all materials specific for Pythium blight. When Pythium is active and the grass is wet, do not mow. Pythium blight weather also means brown patch activity and you will need a different set of chemistry for brown patch management. Stobilurins, DMI’s, polyoxin (Endorse), thiophanate methyl, chlorothalonil are among materials active against brown patch. Both Pythium blight and brown patch are stimulated by high levels of nitrogen.
Submitted by: Dr. Robert Wick