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Eco-Weeder (Puzzy Boy)

The Eco-Weeder is a "weed-burning" device that employs infrared technology to kill weeds. It is manufactured by the Swiss Messerli Sessa, and is marketed and distributed in the U.S. by Forevergreen™, a company dedicated to selling chemical-free weed control products. Forevergreen™ claims that even the most stubborn weeds can be eliminated once and for all with just a few treatments using the Eco-Weeder, with no noise and no pollution. On their website, they also claim that a single person can eliminate weeds at a rate up to 3,000 square meters per hour with minimal fuel consumption. Since The Nature Conservancy of Oregon (with some financial assistance from The Conservancy's Wildland Invasive Species Team) had recently purchased one of these devices, I borrowed the Eco-Weeder and tested it on a few stubborn weeds.

The Device & How it Works
puzzy vs. mullein puzzy vs. thistle
Click the images to see the effects of the Eco-Weeder! (Note that the centers survive.)
The Eco-Weeder uses the combustion of liquid gas in ceramic pyroelements to reach temperatures of up to 1,000 degrees C. This high temperature places intense radiation directly on the weeds and explodes the plants' cells, stopping photosynthesis within a few seconds. According to Forevergreen™, the infrared radiation penetrates only 1 to 2 mm into the soil, and therefore causes little to no damage to soil micro-organisms, while eliminating weeds and pathogenic agents and molds present on the soil surface.

Forevergreen™ states that results are instantaneous, but that previously untreated areas must be treated more frequently at first to be effective. Once a maintenance program has been established, however, these areas can be treated less frequently. They recommend that dry weather and a low degree of relative humidity are the optimal conditions for using the Eco-Weeder, but wet, rainy conditions are also acceptable. Forevergreen™ adds that the Eco-Weeder can control all weeds, but deep-rooted plants will require repeated treatments to achieve full kill.

Eco-Weeders are produced in a variety of different sizes (and prices) ranging from the smallest (the Punto model) for homeowner use costing $225.00, to the largest (the Agri IV model) for agricultural use. The models with wheels can be operated at approximately 1.5 km/hr (1 mph), and stationary machines take about 1.5 seconds to spot-treat a single small plant. It costs about 2 cents to operate per 9 square meters (100 square feet). The Eco-Weeder can be used on many types of surfaces, including stone, paving, gravel walkways, earth and concrete.

A Field Test
I used the Agri Ronco model, which according to Forevergreen™, has an effective width of 200 x 300 mm, uses 0.5 kg/h of gas consumption, outputs 7.8 kW/h, and weighs (without the gas tank) 5.0 kg (11.9 lbs). I measured our infrared plate area to be 135 mm x 365 mm, the propane tank mounted on the backpack to weigh 6.8kg (15 lbs) and the unit with the wheel mounted in front weighed 13.6 kg (30 lbs). This unit was purchased for $1,555.00.

puzzy lowrider Dr. Tu looking casual with her Eco-Weeder
I tried the Eco-Weeder with the wheel mounted on the side as well as in front, and found the front-mount to be the easiest to control. The side-mount required constant pressure on the side-handle to prevent scraping the ground during operation. The front-mount also required constant lifting and attention, but was not as unwieldy as the side-mount. The backpack propane tank was easy to attach to the device (but see sidenote below), the propane hose was of the appropriate length and did not get in the way, and lighting the unit was simple.

According to Forevergreen™, it is not necessary to blacken or incinerate the plants for good kill results, only to turn the foliage dark green--indicating that the cells themselves have exploded. It was difficult for me to tell when sufficient kill was achieved, especially on grasses and sedges. On small seedlings and prostrate plants, the Eco-Weeder performed well, achieving full kill within 30 seconds or so. On perennial plants with a deep taproot or extensive rhizome system, it is unlikely that the plants were severely negatively affected after one treatment. It was difficult to kill the center of the plant (with a deeply buried apical meristem) in perennial or biennial herbs with a basal rosette of leaves, even after a 1.5-minute direct treatment with the Eco-Weeder. In addition, grasses or sedges with any litter material accumulated from past years' growth, may have enough insulating material to protect them from the Eco-Weeder. I found that even after a direct treatment of over 1.5 minutes per plant, that sedges, bunchgrasses, and herbaceous perennials may not have been fully killed by the Eco-Weeder. In order for the Eco-Weeder to be effective against tall plants, the plants will need to be mowed very close to the ground and the surface litter will have to be removed prior to treatment.

puzzy to the rescue!

While Forevergreen™ advertises that their Eco-Weeder is fast and efficient, I found that it took between 10 to 15 minutes to adequately cover a 1 square meter area of low-lying perennial prostrate weeds. I may have been taking more time than necessary at each spot to achieve full kill, but it appears that at this rate it would take several days to treat 1 acre of weeds. On perennial weeds with large taproots or extensive rhizome systems, the Eco-Weeder Agri Ronco model may be less efficient. How well this device actually works on perennial weeds with repeated treatments, remains to be determined. Results will be reported here, within the next year or so.

Sidenote: TNC-Oregon had originally purchased the Eco-Weeder and was sent the device with the assembly instructions in Swiss. The propane attachment of the Eco-Weeder was not readily compatible with standard U.S. propane tanks, and was finally ready for use after obtaining the accompanying propane tank and a few missing attachment parts (which had to be sent from Switzerland). This entire process took several months. Furthermore, paint near the heating element of the Eco-Weeder began to peel-off following only 30 minutes of use.

Safety Notes
puzzy underbits
The Hot Lower Surface
As with all other tools used in weed control, safety comes first! Especially because the Eco-Weeder employs an extremely hot, radiating surface, you should exercise suitable precautions. Be aware of the location of the propane tank, and all ignitable fuels in your work area. Users of this equipment should be prepared and trained to extinguish any fire escapes that may result. While the manufacturers of the Eco-Weeder emphasize that there is little danger in using the Eco-Weeder if used properly and cautiously, I did experience a few small ignitions of plant material, mostly when used over dead leaf material. Unintended ignition of plant material is a particular risk if the Eco-Weeder is being used during times of low humidity and high temperature, i.e. the conditions that Forevergreen™ recommend for most-effective operation of the Eco-Weeder.

Advantages of the Eco-Weeder
  • No permits are required for use.
  • Can be used in areas where there is little or no fine fuel to carry a prescribed burn.
  • Can be used in wet or moist conditions (even when raining!), but works best in dry, low humidity conditions.
  • It is very specific--it can be applied to a single plant, with little or no disturbance to the surrounding vegetation.
  • Proceeding carefully, a single person can use the Eco-Weeder to treat a weed-infested area.
  • Seedlings or small, prostrate, broadleaf herbs are easily killed. Works well in sidewalk cracks or in small areas.
  • Little fuel used, no residual chemicals left in soil.

Disadvantages of the Eco-Weeder
  • An Eco-Weeder, especially a model of sufficient size, can be very expensive.
  • Smaller models may not effective in wildland settings, where there may be much accumulated leaf litter.
  • Does not work instantaneously for deep-rooted plants or for herbs with a basal rosette protecting the apical meristem; may kill these plants after repeated treatments.
  • Mature bunchgrasses, rhizomatous grasses, and sedges are difficult to kill.
  • Damage to native biological soil-crust organisms may be significant.

The Eco-Weeder is a handy (but expensive) device for controlling seedlings or prostrate weeds, especially along sidewalk cracks or in flat, bare areas. It might be very useful in removing weeds from around preserve visitor centers and parking areas. Its utility in wildland settings is limited, especially, where weeds are large, occur in areas with much litter, or are deep-rooted perennials.

More Information
For information on different models, specifications, and purchasing, see the Forevergreen™ website at http://www.chemfree-weedcontrol.com. For personal account information on the Eco-Weeder Agri Ronco model, contact Mandy Tu (TNC-WIST, imtu(at)tnc.org, 503-230-1221)
Debbie Pickering (TNC-Oregon, dpickering(at)tnc.org, 503-230-1221).

--Mandy Tu & Barry Rice, TNC/GIST, January 2002

Updated January 2005
©The Nature Conservancy, 2000