You Are Here: Management Updates 2000 Archive June 9, 2000

Date: June 9, 2000
Category: Diseases
Subject: Red Thread, Leaf Spot/Melting-Out, Bacterial Wilt, Take-All, Anthracnose

Despite the rain, the cooler weather has reduced many of the stress diseases that we often see starting around now. In lawns and grounds, RED THREAD continues to be active. LEAF SPOT is progressing into MELTING-OUT where infections are severe due to excessive moisture and/or excessive nitrogen fertilization. Melting-out often looks like a sunken, sometimes circular area where infection is most severe. Examine individual plants by pulling down the leaves to expose the crown. Look for brown, rotted areas. If many of the plants look badly infected, they are not likely to survive. Overseeding thinned areas with resistant cultivars is probably the most cost-effective approach.

On golf courses, another sample of BACTERIAL WILT on annual type Poa annua (annual bluegrass) was diagnosed, but the turf was growing on very poorly drained, compacted soil that had not been aerated in many years. In other words, the turf was very stressed which probably contributed to the problem. It is notable that the spread of the bacteria followed the mowing pattern exactly. Care to wash mowers thorougly when moving from affected areas many help localize disease problems when they occur.

TAKE-ALL PATCH was also diagnosed on newly established bentgrass in several areas. We now have excellent fungicides for control of these root-infecting fungi, but it is important to deliver the fungicides to the crowns and roots where the pathogen is causing the problem.

ANTHRACNOSE is likely to make an added appearance with the continuing wet weather. Avoid spreading the sticky spores from affected areas to healthy ones. The best chemical control appears to be a DMI fungicide (e.g. Banner, Bayleton, Eagle, etc.) plus chlorothalonil. Many turf problems are not actually specific diseases and have no "spray solution."

- Submitted by: Dr. Gail Schumann