Project Leaders: Tim and Claudia Ferrell, Berry Patch Farm, Brighton, CO
Technical Advisor: Thaddeus Gourd, CSU Adams County Cooperative Extension Service
Project Year: 2002
The purpose of this study was to examine if thermal treatment of weeds will provide effective control on an established certified organic farm. Also, to determine whether steam treatment of crops and field borders in the spring, summer, and fall can reduce annual, biennial, and perennial weeds common along the Colorado Front Range. A flame treatment was compared to a steam treatment for the control of weeds and insects in alfalfa. Steam treatment weed control was investigated for use in non-cropland applications such as irrigation ditch banks, irrigation pipelines, and walkways between beds, edges of the beds, and roadsides. The viability of this project was determined by: 1) researching the importance of application timing of steam or flame treatments for weed control in organic specialty crops; 2) researching the effectiveness of application timing of steam and flame treatments for weed control in non-cropland areas; and 3) determining the economics of flame and steam applications.
The research project looked at three different studies: horticulture crops which includes strawberries, raspberries, vegetables, and orchard fruits; agronomic crops including alfalfa; and non cropland, including irrigation ditches and pipes, and fence lines.
The experimental design and treatments for weed management for each of the horticulture crops included: one steam application, three steam application, six steam application, hand-weeded treatment, mechanical application, and the untreated check (control).
The experimental design and treatments for the agronomic crop (alfalfa) included: steam application, flame application, and the untreated check (control)
For the non cropland, the treatment included: steam application, flame application, tillage, and the untreated check (control).
Flame versus Steam treatment- advantages
Steam treatments allow one to eliminate fire risks and flame damage to sensative environments. The use of steam also eliminates the potential of human or wildlife exposure to pesticide residues and does not contaminate water, air, or soil.
The Atarus Ranger thermal weed control device (for flame treatments) uses propane for fuel. It weighs forty pounds and supplies 45 minutes of use per tank of propane when used on a high setting. This piece of equipments costs $550.
The Sioux Weed Blaster Steamer weed control device uses diesel as a fuel source. It applies two gallons of water per minute which produces 350 degree F saturated steam at 250 psi and it holds 125 gallons of water. This piece of equipment costs $4,000.
The weed control methods were tested for the horticulture crops on peaches and strawberries. The weeds tested on for the peaches were kochia, lamsquarter, rye, and alfalfa. The mechanical treatment worked best to eradicate rye and alfalfa, controlling about 90% of each. The flame treatment worked, controlling about 65% of kochia and lambsquarter. The steam treatment was ineffective, only controlling about 10% of all weeds. The weeds tested in the strawberries were kochia, dandelion, and downy brome. At the end of the testing, it was shown that hand weeding killed most weeds, from 80-90%. The steam application (3 treatments) was successful at eradicating 85% of downy brome. Dandelion and kochia did not respond to the treatment, controlling 50% and 15%, respectively.
Annual weeds of alfalfa include kochia and netseed lamsquarter. In this part of the project, the use of the herbicide Pursuit was used in comparison to the steam, flame, and untreated applications. Shown by this test, the flame treatment performed best, getting rid of about 95% of kochia and 90% of netseed lambsquarter. The steam and Pursuit treatments were ineffective.
In the perennial non-cropland, the flame treatment averaged 87.5% control after two applications on stinging nettle, scouringrush, and poison hemlock. After four applications, the treatment averaged 97.25% control of stinging nettle. Poison homelock was controlled with just three applications. Twenty-five days after the fourth treatment, the average control of stinging nettle was 93.75%. Poison hemlock was completely controlled, and scouringrush averaged 85% control.
In the annual non-cropland testing, 13 days after the second flame treatment, the average control of kochia was 99.5%. Twenty-seven days after the second treatment, the averaged control of kochia was 98.5%. These two treatments of flame gave excellent control of kochia for 68 days following the second application.
A comparison was done between the steam and flame treatment on perennial weed control of poison hemlock and stinging nettle. Nine days after the first application of steam and flame, the flame treatment showed fair activity on stinging nettle and good activity on poison hemlock. At this time, the steam application showed very little activity on either stinging nettle or poison hemlock. The evaluation of weeds taken nine days after the second application of flame showed greater than 83% control of stinging nettle and 88% control of poison hemlock. The steam treatment showed 21% control of stinging nettle and 42% control of poison hemlock. Twenty-five days after the second treatment, stinging nettle and poison hemlock control dropped to 77% in the flame treatment. No poison hemlock or stinging nettle contol was observed in the steam treatment 25 days after the second application.
These results, specifically the ineffectiveness of the steam treatment and the herbicide Pursuit, may be attributed to the drought conditions at the time. It was shown that the flame treatment is the most effective in weed control.