Flame weeders are used by a few Ontario farmers but in general have not been popular in this area. There are both hand-held flame units and larger ones that are pulled behind the tractor. Units vary in size, and the speed of operating ranges from 4-7 km/hr.

This technique works by rupturing plant cells when the sap rapidly expands in the cells due to heating. After flaming weeds may at first look unaffected, and then will wilt and die later in the day, similar as if they were injured by a morning frost.

Weeds are most susceptible to flaming when they are seedlings, 1 to 2 inches tall. Bigger weeds will not be killed and will regrow. Broadleaf weeds are more susceptible to lethal flaming than grasses. Grasses develop a protective sheath by the time they are approximately 1 inch tall and may require a second flaming. Perennial weeds may be suppressed but generally regrow and are not controlled.

Crops are sensitive after the growing point emerges from the soil. The correct stage to safely flame crops will vary with species. Broadleaf crops can be particularly sensitive to the flame and care should be taken with these crops. To protect crops, either direct the flame away from the crop or use a protective shield to keep the flame off the crop leaves.

Two websites that give more information are:

http://attra.ncat.org/attra-pub/flameweedveg.html

Red Dragon - http://www.flameengineering.com/Agricultural_Flaming_Guide.html

Hugh Martin

OMAF, Organic Crop Production Lead