You Are Here: Management Updates 1999 Archive July 2, 1999

Date: July 2, 1999
Category: Diseases
Subject: Gray Leaf Spot, Curvularia Blight, Brown Patch, Dollar Spot

Disease Alert:
Jim Skorulski, USGA Agronomist, alerted us that GRAY LEAF SPOT of perennial ryegrass has been reported in Virginia. Watch perennial ryegrass carefully for any unusual problems, especially when other turf species appear healthy. One symptom is the wilting, "fish-hook" symptom. See the photo on the cover of the current issue of the Green Section Record, but keep in mind that other leaf spot fungi can cause similar symptoms. Gray leaf spot usually appears first in higher cut turf, such as roughs, and may appear as drought symptoms. Early fungicide applications are very effective. Send any suspicious samples to the UMass Turf Diagnostic Lab for confirmation. Please call - Submitted by: Dr. Gail Schumann if you have other questions- (413) 545-3413.

Many recent turf problems have been related to the very dry conditions of June. The turf was affected not only by the lack of rainfall, but by the extremely low relative humidity. A number of samples contained plants with straw-colored outer leaves, but healthy green centers and no active fungal problem. CURVULARIA BLIGHT was identified in stressed fairway Poa annua (annual bluegrass) where environmental stress was followed by heavy rain and extended humid conditions. This problem responds well to standard foliar fungicides, but they need to be applied frequently where heavy thunderstorms occur repeatedly over several days. BROWN PATCH and DOLLAR SPOT were active with the advent of wetter weather.

This was probably the worst June in many years to be trying to establish turf. In bentgrass, TAKE-ALL PATCH and PYTHIUM ROOT ROT were diagnosed. Many other fungi will attack young seedlings in moist conditions, and the young plants are particularly vulnerable because they are less able to withstand environmental stresses compared to established turf.

In lawns, insufficient irrigation has allowed leaf spot fungi to cause MELTING-OUT. Some NECROTIC RING SPOT has been identified, particularly in stressed areas. FUSARIUM BLIGHT- a foliar disease that can lead to crown and root rot in relatively large, ill-defined patches- was identified where turf was stressed and excess water had been applied. Excess N fertilizer will exacerbate this problem.In well-fertilized and well-watered perennial ryegrass lawns, PYTHIUM BLIGHT has been a problem.

The holiday weekend will be a challenge for turf managers- hot, humid and frequent rain- the perfect situation for fungal disease outbreaks.

- Submitted by: Dr. Gail Schumann