Pythium Efficacy Summary – 2022

Collapsed roots of columbine in potting media with Thielaviopsis     Research Summary Abstract

At the IR-4 Environmental Horticulture Program Workshops in 2009 and 2019, Pythium Efficacy was selected as a high priority project to expand the knowledge and list of fungicides available to growers for these diseases. In addition to research collected through the IR-4 program, this summary includes a review of experiments conducted from 1999 to 2013 on environmental horticulture crops. During this time period, numerous products representing 47 active ingredients were tested as drench, foliar or soil applications against several Pythium species causing root rot and damping-off. Pythium species tested included: P. aphanidermatum, P. irregulare, P. dissotocum, P. ultimum and P. vipa. Most trials were conducted on P. aphanidermatum and P. ultimum. Although there were insufficient data for definitive conclusions, several relatively new products that are included in the Pythium efficacy project looked promising for managing P. aphanadermatum. These were BW159, BW161N, Daconil ZN, MBI-121, Picarbutrazox 20WG and Picarbutrazox SC. The established standards and recently registered materials (Adorn, Fenstop,Subdue Maxx and Terrazole/Truban) generally performed well. The data from these trials suggest that the effectiveness of some fungicides in controlling Pythium root rot may vary, depending on the species of Pythium or crop.

Link to Summary: Pythium Efficacy