You Are Here: Management Updates 2008 Archive July 30, 2008

Date: July 30, 2008
Category: Diseases
Subject: Fungicide Efficacy Influenced By Rainfall

Application of fungicides is a crucial part of disease management on golf courses.  The success of a fungicide application is significantly influenced by many factors before, during, and after application.  Particularly, paying attention to weather forecasts prior to a fungicide application is very important since we have had frequent heavy rain events over the past few weeks.  Here are some general rules to follow:

1. Avoid application when rain is expected.
   
   
2. Contact fungicides (for example, chlorothalonil, mancozeb) are always more sensitive to rainfall or irrigation than systemic fungicides, because their mode of action relies on drying on the leaf surface.  Failure of a contact fungicide to dry on the leaf surface may result in a loss of efficacy.
   
   
3. Systemic fungicides (for example, thiophanate-methyl, boscalid, ipodione, propiconazole) are not as sensitive as contact fungicides, but need a minimum of 3 hours of drying time prior to rainfall or irrigation.
   
   
4. Fungicide formulations containing different sticking agents may vary in effectiveness if post-spray rainfall occurs.

Submitted by: Dr. Geunhwa Jung

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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