The Bioherbicide Phoma macrostoma: A Glimpse Into the Future for Broadleaved Weed Control in Turfgrass

by Karen Bailey and Louis Simard

A healthy, green lawn is not only pleasing to the eye, but also provides other benefits to people and the environment.

Grass cleanses our air by neutralizing pollutants, diminishes soil erosion, traps dirt and dust, moderates temperature and noise, and creates a pleasant surrounding. Weeds in turf compete for light, nutrients, moisture, and physical space disrupting the uniformity and the vigour of the grass.

Legislative changes across Canada often restrict the types of herbicides that may be used in urban areas, but Phoma macrostoma is a new bioherbicide that received full regulatory approval in 2016 by the Pest Management Regulatory Agency for its use in turfgrass to control many broadleaved weeds.

Phoma is a fungus indigenous to Canada that causes affected plants to come up white and eventually die. It was discovered by scientists with Agriculture & Agri-Food Canada in Saskatoon. Host range testing showed that broadleaf weeds such as Canada thistle (Cirsium arvense), dandelion (Taraxacum officinale), scentless chamomile (Matricaria perforata), chickweed (Stellaria media), and white clover (Trifolium repens) were damaged by the fungus, but grassy weeds were not harmed.

Environmental fate studies have shown no dispersion of the pathogen from the area of placement and a low risk of survival from year to year. Field testing across Canada and the USA have determined the application parameters to obtain good efficacy under a broad range of environments when used as either a pre-emergent or post emergent application.

Phoma may be applied from spring through fall when the mean day time air temperature is between15-30°C and the soil is relatively moist. Extreme moisture events around application may reduce the level of weed control attained, especially on sandy soils. The bioherbicide may be applied with commercial granular fertilizers and result in a 10-15% enhancement in weed control.

Recently, the bioherbicide was licensed to Premier Tech who is working to bring this innovation to the market place. Efforts are currently made to optimize the processes and the industrial scale production of the fungus.