Phoma macrostoma: An update on the new turfgrass bioherbicide

K.L. Bailey (Agriculture & Agri-Food Canada, Saskatoon) and S. Falk (The Scotts Company, Marysville, OH)

For several years, the fungus Phoma macrostoma has undergone extensive evaluation by Agriculture & Agri-Food Canada and The Scotts Company to see if a bioherbicide could be developed to control broadleaved weeds in turfgrass. In 2009, the summer issue of Sports Turf Manager reported on its discovery as a potential bioherbicide, and some of the research demonstrating its efficacy and crop safety.

In June of 2011, the Pest Management Regulatory Agency approved a conditional registration for Phoma macrostoma to be used domestically and commercially for control and/or suppression of weeds such as dandelion, scentless chamomile, English daisy, white clover, black medic, Canada thistle, chickweed, broadleaf plantain, and ragweed. The bioherbicide may be used safely on a variety of turf types such as Kentucky bluegrass, bent grass, perennial or annual ryegrasses, fescues, bromegrasses, timothy, and Bermuda grass.

The fungus is formulated into granules which may be applied to either newly-seeded or well-established lawns from a ready-to-use applicator for spot treatments or by broadcasting the granules as either pre-emergent or post-emergent applications. The product may be applied anytime from spring through fall, but it works best when the mean day time air temperature is hovering above 20°C (15-30°C range) and the soil is relatively moist. The product does not need to be “watered-in” but some precipitation or irrigation (up to 1-3 inches) within 24-72 hours after application would be beneficial particularly if the soil is not friable or moist.

Continuing research has expanded our knowledge of how the bioherbicide will perform in the field. Studies have shown that extreme moisture events around application will reduce the level of weed control attained, especially on sandy soils. The bioherbicide may be applied at the same time as commercial granular fertilizers which may result in a 10-15% enhancement in weed control.

Currently, Phoma macrostoma is undergoing scale-up development to be able to efficiently produce commercial quantities and so a commercial launch is still a few years away.

Additional Reading Zhou, L., Bailey, K.L., and Derby, J. 2004. Plant colonization and environmental fate of the biocontrol fungus, Phoma macrostoma. Biological Control 20: 634-644.

Bailey, K.L., Pitt, W.M., Derby, J., Walter, S., and Taylor, W. 2010. Efficacy of Phoma macrostoma a bioherbicide for control of dandelion (Taraxacum officinale) following simulated rainfall conditions. The Americas Journal of Plant Science and Biotechnology 4 (Special Issue 2): 35-42.

Bailey, K.L., Pitt, W.M., Falk, S., and Derby, J. 2011. The effects of Phoma macrostoma on nontarget plant and target weeds species. Biological Control 58 (3): 379-386.

Bailey, K.L. and Falk, S. 2011. Turning research on microbial bioherbicides into commercial products – A Phoma story. Pest Technology 5 (Special Issue 1): 73-79.