You Are Here: Management Updates 2006 Archive May 3, 2006

Date: May 3, 2006
Category: Diseases
Subject: Basal Rot Anthracnose, Pythium-Induced Root Dysfunction

Two diseases have occurred repeatedly in specimens submitted to the UMass Extension Plant Diagnostic Lab recently: basal rot anthracnose and Pythium-induced root dysfunction (not Pythium root rot).

Anthracnose basal rot is caused by Colletotrichum graminicola. The fungus survives as a saprophyte in plant debris or as a pathogen in infected tissue and attacks turf growing under low fertility, temperature stress, or both. The disease is most severe in areas of poor drainage, heavy traffic, and soil compaction. C. graminicola usually infects grass blades from the tip down, especially freshly mowed grass and can be present on the leaves, roots, or stolons. Basal rot can be extremely difficult to suppress when it becomes a chronic problem on annual bluegrass greens. Increase mowing height, divert traffic from affected areas, and avoid potentially abrasive grooming practices such as double-cutting, aeration, and brushing. Anthracnose can be managed with light nitrogen applications and fungicide applications. For curative sprays, always include a high rate of chlorothalonil in the mixture. Tank mix with azoxystrobin (Heritage™), fenarimol (Rubigan™), propiconazole (Banner™), or Al-phosphonate (Signature™). Greens should be spoon-fed weekly with nitrogen to encourage the growth and spread of healthy bentgrass in mixed stands of Poa and bentgrass.

Pythium problems have been seen in shaded areas or areas with poor drainage. Pythium-induced root dysfunction is caused by many species of Pythium and can become a chronic problem on old annual bluegrass greens in northern areas due to the greater susceptibility of Poa to ice and low temperature injury. Symptoms mimic basal rot anthracnose; leaves appear yellow to brown and are prone to wilting before plants die. Death of plants results from a combination of disease and the mechanical injury from mowing stressed plants with dysfunctional roots. This disease must be managed by a combination of cultural and chemical means. Drying the soil is essential; reduce automatic overhead irrigation and syringe on an as needed basis. Affected greens should only be mowed when dry, preferably with a lightweight walk-behind mower. Never mow on rainy days or when soil is excessively wet. Increase mowing height to 4 mm and reduce mowing frequency to 4-5 times/week. Avoid other mechanical stresses by delaying top-dressing, brushing and aeration until the turf shows signs of recovery. Apply foestyl-Al + mancozeb (Signature™ + Fore™) followed in 5-7 days with an etradiazole (Koban™) or chloroneb (Terraneb SP™) drench. Or, alternate metalaxyl (Subdue™) and propamocarb (Banol™) applications on a 10-14 day schedule. Be sure to water in all the mentioned fungicides except Signature™ + Fore™. Applications of biostimulants or micronutrients may be beneficial.

Submitted by: M. Bess Dicklow

DISCLAIMER - As always, it is the responsibility of the applicator to verify the registration status of any pesticide BEFORE applying it. Different states have different regulations as well. The author and the University of Massachusetts are not liable for any consequences of any pesticide "recommendations". Mention of any trade name is not to be considered endorsement of a product.

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