You Are Here: Management Updates 2000 Archive June 2, 2000

Date: June 2, 2000
Category: Diseases
Subject: Leaf Spot/Melting-Out, Dollar Spot, Fairy Ring, Bacterial Wilt

We are seeing a mixture of the end of spring diseases and the beginning of early summer diseases at this time. In many areas of excessive moisture LEAF SPOT has progressed to MELTING-OUT. If crown and roots are badly infected, plants may not recover, but the drier conditions will favor recovery of many plants.

RED THREAD continues to be common on golf course fairways and lawn areas.

DOLLAR SPOT is active in many areas. This is the most common disease for which fungicide resistance is a problem. Golf courses should be using a fungicide rotation to avoid this problem. COTTONWOOD TREES are producing their "cotton" these days which can be mistaken for dollar spot mycelium. If you role the "cotton" between your fingers, you can feel the fibers. Dollar spot mycelium will disappear immediately when touched.

FAIRY RING is also common. The "rings" can be round or very irregular, with or without mushrooms, with or without browning. Fairy ring is the only cause of extra greening at the leading edge of areas. Brown rings alone can have other causes. If you choose to apply a fungicide for fairy ring, keep in mind that the mycelium is in the soil and may be hydrophobic. Spiking or aeration followed by watering in of the fungicide is necessary.

In hopes that this report does not create a panic, one sample of a very early stage of BACTERIAL WILT on Poa annua (annual bluegrass) was diagnosed. The disease begins as small reddish spots. The bacteria clog up the vascular tissue of the plants (the xylem). Junction is labelled for disease control and contains copper hydroxide which may help protect plants or prevent spread by foot traffic. The disease is specific to Poa annua and only certain types of it (mostly the annual types). There is no real cure for a bacterial disease of turf because of the nature of its management- frequent mowing that wounds the plants and spread the bacteria to the wounds. There is speculation that the disease is increasing because of low mowing heights which stress the plants and increased use of sand topdressing which causes wounds for entry of bacteria.

- Submitted by: Dr. Gail Schumann