Under the microscope: Pythium blight

Pythium blight (pathogen: Pythium spp. P. aultimum, P. aphanidermatum) during hot humid weather can be a serious problem on creeping bentgrass (Agrostis stolonifera) and annual bluegrasss (Poa annua) greens and to a lesser extent bermudagrass (Cynodon dactylon). Generally, this disease is most severe on turf sites that are wet or poorly drained and where the turf is under summertime stress. These areas include high traffic areas where compaction occurs, like the ends of fairways where mowers may turn. On tees, Pythium blight may initially appear around divots where the turf is under additional stress.

Pythium blight is active when temperatures occur between 86 and 95 F and nighttime temperatures remain above 70 F. However under extremely humid and wet conditions Pythium blight will occur at nighttime temperatures below 70 F. The risk of Pythium blight increases on turf growing in low-lying areas where water accumulates, on compacted soils, and on thatchy turf.

Symptoms on putting greens normally start off as small patches that rapidly increase in diameter becoming more irregular shaped. If you rub some of the leaves early in the morning they will appear oily (thus, the common name “grease spot”). Leaves become a light tan color as they shrivel. The leaves can become matted and covered with a white mass of mycelium. Generally speaking fungicide control is most effective when applied preventatively.

-- Karl Danneberger, Ph.D.

Focusing Irrigation on Priority Areas

In case you missed it, here's yesterday's Puttin' Down Roots, by Karl Danneberger.

What do you think? In times of drought, does the rough deserve a drink? Leave us a comment below! 

With drought conditions hitting many parts of the United States this year, watering is a critical issue not only in the amount available but how it should be used. In areas where water is limited, prioritize the critical areas on a golf course that need to receive water. Obviously, greens are at the top of the list, followed by tees.

But from a golfing perspective, areas like greens surrounds/complex and associated fairway and rough landing areas may need to be considered. The green complex provides not only a visually aesthetic area but also an important area for playability. Golfers don't want to miss the putting surface by a few yards and see their golf balls bounce 30 to 50 yards away.

One of the most difficult areas to decide how to water is fairway landing areas. In some cases where water is plentiful even with a drought, the tendency is to overwater. This results in the ball plugging or causes little roll. To the golfer this is extremely disappointing, especially if a playing partner misses the fairway slightly but gets an additional 30 yards because of drought conditions in the rough.