Evaluation of Thermal Weed Control Units for
Selected Weed Species

Researchers
Dr. Nabil Rifai & Dr. Tess Astatkie (NSAC)
Dr. Magda Lacko-Bartosova & Dr. Jan Gadus (Slovak Agricultural University in Nitra)

Research Assistants
Mr. Pavol Otepka & Mr. Ladislav Kosik (Slovak Agricultural University in Nitra)
Mr. James Miller (NSAC)

Background
Thermal Weed control is being developed to provide alternative options for weed management systems. It is used mainly in organic farming for pre-emergence control in slow germinating row crops. In some heat tolerant crops, selective post-emergence treatment is also used. Selectivity can be obtained by directing the heat toward the weeds and away from the crop. The high temperature damages the cellular structure and kills weeds within several hours or few days. First signs of the effectiveness are change of leaf colour and plant withering.
     The three thermal units evaluated in this study were based on flame, infrared radiation and hot water-steam. Flame based thermal units are the most developed with several companies producing "Open Flame Burners". Infrared technology is also rather advanced with several companies producing "Covered Infrared Radiators". Hot steam is currently the least available of the three methods.

Objectives
To evaluate the efficacy of the Flame, Infrared Radiation and Hot Steam thermal units for control of the selected weed species: Amaranthus retroflexus L. (redroot pigweed), Chenopodium album L. (common lambsquarters), and Persicaria maculata (Raf.) S.F.Gray (spotted ladysthumb). Sinapis alba L. (white mustard) was also used as a crop with significant characteristics of weeds.

Duration
This project started in April 2002 and is to be completed in August 2003.

Preliminary Results
The infrared radiation technique is the most effective method, because it reaches highest temperature during treatment. Weeds are mostly destroyed in every life stage, but some perennial weeds can be more resistant. It is necessary to set up the most suitable driving speed to ensure adequate performance. This method can be useful for crops with large row spacing, such as orchard, vineyards etc.
     Flaming should be used as soon as weeds appear in the crop. Larger weeds may survive the flame treatment, because flame is not as intense as the infrared radiation technique but it has more adjustable parts, therefore the heat distribution can be directed toward weeds and away from the crop.
     Hot water-steam reaches the lowest temperature, which means it poses less danger to the crop. This also means it is very important to treat weeds at very slow driving speed when they are in the youngest life stage. The hot water-steam system may be effective when used within an integrated programme using a variety of cultural, physical, mechanical and biological practices to solve the weed problem.
     This experimental work shows thermal weed control is a suitable support especially for organic farmers

Partners
The Organic Agriculture Centre of Canada (OACC) & the Natural Sciences and Engineering Research Council (NSERC) funded this project.