You Are Here: Management Updates 2000 Archive August 25, 2000

Date: August 25, 2000
Category: Diseases
Subject: Gray Leaf Spot, Black Layer, Leaf Spot, Dollar Spot, Rust

The big news this week is the confirmation of GRAY LEAF SPOT (GLS) in a golf course rough in eastern MA. None of the 10 research cooperators have GLS as of the 8/21 sampling. No other samples have been diagnosed. This confirms that we still don't have all the answers for this disease. GLS often begins in the roughs and then develops in the fairways. The area may look droughty despite adequate soil moisture. The disease is specific to ryegrass, so the Poa annua and other grasses will look healthy. Unfortunately, other "routine" leaf spots are commonplace this year, so accurate field diagnosis is difficult.

On golf courses, many greens with poor drainage are showing the effects of too much rain and many rounds of play. When the soil is broken open, the unmistakable odor of ANAEROBIC CONDITIONS and BLACK LAYER confirm that the roots are not getting enough oxygen to grow and function. Aeration, tree pruning, improved drainage are the only solutions. Many complaints have come in about difficult fungicide control of DOLLAR SPOT. The rapid growth and excessive rain have minimized control intervals, but keep in mind that repeated application of products from the same penetrant chemical group can also reduce control due to resistance.

On lawns, LEAF SPOT and RUST are commonly seen. It is difficult to minimize leaf moisture this year, so fungi are very active. At least, the moderate temperatures favor overseeding and re-establishment.

- Submitted by: Dr. Gail Schumann