Colletotrichum sp: A potential candidate for biocontrol of scentless chamomile (Matricaria perforata) in western Canada

Abstract

Based on an assessment of 706 fungal isolates obtained from Canada and Europe, a group of Colletotrichum sp. isolates, tentatively identified as C. truncatum, was moderately efficacious for biocontrol of scentless chamomile (Matricaria perforata). In this study, 19 C. truncatum isolates, 11 from Canada and eight from Europe, were compared for virulence, crop safety, and minimum dew requirement for infection to narrow the selection of candidates. Applied at 1×10⁶ spores mL⁻¹, these isolates expressed variable virulence under controlled environments, with slightly higher variations observed on the Canadian isolates. There was also a slight difference in host specificity among the isolates tested; most isolates caused disease only on chamomile species (M. perforata and M. recutita) but two Canadian isolates also infected lentil, flax, or both. At 20°C, most isolates required more than 20 h dew for maximum infection. This requirement can be an impediment for using this fungus as a biocontrol agent in western Canada where the climate is semi-arid. Treatment of scentless chamomile at the 10-leaf stage with the herbicide metribuzin 48 h prior to fungal inoculation increased weed control to 72%, compared to 40 and 47% by the herbicide and fungus applied alone. However, a similar treatment using the herbicide bentazon did not enhance the weed control significantly as compared to the herbicide alone.

Keywords:

• Matricaria perforata
• scentless chamomile
• biological control
• bioherbicide
• Colletotrichum truncatum
• host specificity
• synergy

Acknowledgments

This research was partially funded by grants 19990354 and 20000051 from the Agriculture Development Fund, Saskatchewan Agriculture, Food, and Rural Revitalization, and we are grateful for the financial support. The authors also wish to thank S. Leung, K. Jackson, and M. Molloy at AAFC Saskatoon Research Center, and M. Cripps, J. Hiltbrunner, and J.P. Marelli at CABI Bioscience, Switzerland for their technical assistance.