Botrytis bunch rot, caused by Botrytis cinerea, poses significant challenges for grape growers. This blog explores findings from the 2006 UC Davis study on chemical and biological control of Botrytis bunch rot in grapes, conducted by W.D. Gubler and his team.

Study Overview

The 2006 grape bunch rot trial was carried out in St. Helena, Napa County, California. The primary objective was to evaluate the efficacy of various fungicides in controlling Botrytis bunch rot. The study utilized a randomized complete block design with multiple treatments, including chemical fungicides and biological control agents.

Key Researchers:

  • Principle Investigator: Doug Gubler, Ph.D.
  • Researchers: Ken Asay, Chris Janousek, Ph.D.

Materials and Methods

Trial Layout:

  • Vineyard: Established in 1991, Johannesburg Riesling variety.
  • Application Method: Backpack sprayers.
  • Replicate Units: Each treatment replicated on 3 vines.
  • Evaluation: Disease severity and incidence measured post-harvest.

Fungicide Treatments:

  • BioNatrol-M + Latron B-1956: A natural fungicide tested at 1400 ml/acre and 1841 ml/acre.
  • Conventional Fungicides: Included V-10135, Vangard, Endura, and more.


The study revealed significant differences in disease severity among treatments, although there was no effect on disease incidence. BioNatrol-M and Vangard treatments exhibited the lowest disease severity, indicating their potential effectiveness in managing Botrytis bunch rot.

Key Findings:

  • BioNatrol-M: Reduced disease severity significantly, demonstrating its effectiveness as a natural fungicide.
  • Vangard: Also showed low disease severity, making it a strong contender among conventional fungicides.


The 2006 UC Davis study underscores the importance of integrated pest management strategies, combining chemical and biological control methods to manage Botrytis bunch rot effectively. BioNatrol-M stands out as a promising natural fungicide, offering an eco-friendly alternative to conventional treatments.