Hardwood stump sprouts and suckering present a serious problem for pre-commercial thinning. With the benefit of a well-established root system, they can grow as much as two meters of stem in one growing season. If pre-commercial thinning is carried out in a stand with an average height of three meters, after a couple of summers it may be difficult to believe the stand had ever been touched. Wait for the average height of hard-wood stems to reach five or six meters before thinning, and it' s harder to get cut trees to fall to the forest floor. Additionally, very tall, thin trees left standing will be heavily damaged by snow and ice loads.

A new device developed by New Brunswick forester Aboud Mubareka may change all that. His Sprout-less Applicator is a thinning saw attachment which supplies the cutting blade with small amounts of herbicide as needed.

Thinning saw attachments themselves are not new. In the I970s and '8Os, attachments were developed which applied herbicides to cut stumps by dripping herbicide on the blade. The assembly consisted of a tank of herbicide carried on the saw operator's back and a hose running from the reservoir to the blade. This system presented several drawbacks. The tank was heavy and awkward to carry. The hose was susceptible to tangling in brush and breaking. Flow rate was not easily adjustable and if the saw remained at idle, herbicide would build up on the blade and would spin off, spraying the operator.

Mubareka, a native of Iraq who studied forestry in Germany, has worked for Fraser and as a silviculture contractor in New Brunswick and Maine since 1974. He saw the need for an efficient, economic and safe tool for applying herbicide in hardwood pre-commercial thinning. The reservoir holds 110 cc of herbicide and weighs just 500 grams (1.1 pound). No modifications to the saw or blade are require. Depending on the density of cut stems, one reservoir will last between one and three saw re-fueling.

In 1993-94, Mubareka experimented with various materials for the all-important gasket. With the vibration of the cutting blade, herbicide seeps past the gasket and across the bottom of the blade, applying a thin film of herbicide to the top of cut stumps. When the saw is idling or revving up between cuts, there is not enough vibration to allow herbicide to seep between gasket and blade. A possible exception, Moberaka says there may be a small amount of leak age from vibrations set up when, in tuning the saw, it is brought to maximum RPM.

When operated properly, the Sprout-less Applicator emits no spray, mist or fog. The system minimizes the chance of contamination or spills that might affect the operator or the environment' When the operator sees that too much herbicide is seeping onto the blade, it is time to install a more restrictive gasket. Twelve gaskets are available for adjusting the flow rate for various herbicides (and mixes of herbicides) with varying densities. Temperature changes through the day, especially in the autumn, can also affect density and flow- rate.

The Sprout-Less Applicator provides two significant advantages: efficient use of herbicides, and an overall reduction in the amount of herbicide necessary to control hardwood brush. Application rates of Killex (for testing purposes only) using the Sprout-less Applicator averaged 0.72 liters per hectare, compared with the recommended aerial application rate of 12.50 liters per hectare. The suggested aerial and backpack application rate for Vision is six liters per hectare, while Sprout-less Applicator rates were around half a liter per hectare.

The National Research Council and the Research Productivity Council have assisted Mubareka with tests that were conducted in 1990,1995 and 1997. Trials conducted in New Brunswick, Nova Scotia. Ontario and Maine used a variety of herbicides at varying concentrations and application rates. One trial using Release herbicide resulted in a 98-percent control of sprouts, with sprouts that did grow reaching only 10 centimeters in height. In the control area of the trial, where no chemical was applied, sprouts reached 45 centimeters in height.

Because of the complicated nature of the gasket that meters the herbicide, and the risk that in appropriate metering would present, Mubareka requires that Sprout-less Applicator operators be trained and licensed (he undertakes the training himself, working directly with the saw operators). A company using the Sprout-less Applicator requires the same application permits as for conventional aerial or backpack operations.

With more and more jurisdictions across North America restricting aerial application of herbicides, Mubareka, who lives in St. Joseph, Madawaska County, sees a bright future for his applicator as the safer and more efficient alternative

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Articles de journaux

"Le Madawaska", (New Brunswick) June, 1997

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"Forest Engineering Insitute of Canada field note" (Juillet 1999)

July 1999

Field Note No.: Silviculture-117

Previous Reference Sheet No.: None

The Sprout-Less Herbicide Applicator

by Luc Desrochers, F.E., Researcher

Introduction

Aboud Mubareka, a forester and silvicultural contractor, developed a brush saw-mounted device called the Sprout-Less Herbicide Applicator that can be used to apply herbicide to the stump during cutting. Unlike other brush saw-mounted devices developed in Finland in the 1970s (the Windsor/Enso Stump Treater and the TT Brush Saw-mounted Stump Treater), the Sprout-Less applicator does not produce a spray; thus, it can potentially permit low herbicide-application rates. The device is rugged and simple to use, and it requires little or no modification of the brush saw. To date, models have been manufactured for most commonly used saws. In August 1998, FERIC conducted a short-term study of two operators using the device for plantation cleaning on Fraser Papers Inc.'s limits near Edmundston (N.B.).

Tool description

The Sprout-Less Herbicide Applicator consists of a cup-shaped reservoir and a valve system that attaches beneath the brush saw's blade using the existing bolt and nut. It measures approximately 10 cm in diameter, holds 110 mL of herbicide solution, and weighs about 500 g when full. The reservoir was designed to be refilled via two small plugs when the operator refuels the brush saw. The applicator is activated by vibration of the saw's blade. A set of gaskets between the reservoir and the copper cap prevents the herbicide from seeping out until the vibration levels rise above a certain level (i.e., when cutting a stem); at that point, a gap forms between the cap and the reservoir and lets the herbicide solution seep out and spread across the bottom of the blade. Available gasket combinations can match the flow rate to a variety of herbicide mixtures of different viscosities. Gaskets must be replaced approximately every 12 refills, depending on the site and stand conditions and on how fast the gaskets become clogged with dirt or herbicide residues. In 1999, the Sprout-Less Herbicide Applicator cost $695 per unit, including five sets of gaskets. Gaskets cost $36 for 12 sets.

Description of the site and the operation

The study site was approximately 20 km north of Edmundston. After harvesting in 1989, it was planted with black spruce in 1991. The stand density was 20 200 stems/ha, with an average height of 2.2 m and a softwood stocking of 45% (1125 stems/ha); 86% of the crop trees were overtopped by hardwood competition (based on survey data from Fraser Papers Inc.). The target application rate with the Sprout-Less Herbicide Applicator was 55 mL of herbicide solution per refill (75% VisionÒ ). Operators were instructed to change the gaskets whenever less than 30 mL had been applied between two refuelings of the saw. Two operators, who used Stihl FS 420 and FS 550 brush saws, were timed simultaneously over a period of 3 days. They worked in sections approximately 400 m apart, with slightly different vegetation covers.

Results and Discussion

The treatment reduced stand densities from 23 600 and 18 250 stems/ha to 2620 and 2210 stems/ha, respectively. Operators reported that they had to slightly modify their normal working technique, but this was not evident during the study. The operators worked for a total of 17.3 and 22.3 Productive Machine Hours (PMH) to treat 1.16 and 1.27 ha, respectively, with resulting productivities of 0.07 and 0.06 ha/PMH (Table 1). The work cycle included the time between refuelings as well as the refueling itself, and ranged between 50 and 110 minutes. Refilling the applicator's reservoir took between 2.4 and 11.1 minutes, and averaged less than 5 minutes. Operators changed the gaskets about every 12 refills (roughly every second day) and took between 8 and 13.4 minutes to make this change. Servicing the applicator (refilling it with herbicide and changing the gaskets) accounted for 6.5 and 7.5% of total PMH, respectively, for the two operators.

Herbicide refills required between 30 and 100 mL and averaged 61 and 80 mL, respectively, for the two operators. The estimated flow rates were 0.82 and 1.34 mL/minute, respectively, for corresponding application rates of 0.63 and 1.14 L/ha for the two operators. The difference between the two application rates can be explained by the stand conditions, operator work habits, and the setup of the device itself; however, it was not possible to determine which factor most affected the application rate during the study.

The estimated direct cost for the Sprout-Less Herbicide Applicator itself is $17.45/ha assuming a working life of 1000 hours and gasket replacement every 12 gas refills. Under a less-favorable scenario (a working life of 360 hours and gasket replacement every 8 refills), this cost would increase to around $58/ha. This cost is still relatively low compared with that of aerial or ground-based foliar herbicide applications. However, the permits and certificates required by herbicide users in certain provinces could discourage the use of the applicator.

Conclusions

The Sprout-Less Herbicide Applicator appears to be a promising tool; it is simple, sturdy, and easy to use. FERIC's study showed that only 6.5 to 7.5% of the total PMH was attributed to maintenance of the device. Workers were required to adjust their work habits, but no effect on productivity was evident in this study. Development work to improve the design is still necessary, especially in terms of gasket selection and assembly, because proper calibration of the device poses problems and the device must be adjusted for different operators and sites. The overall treatment cost with the Sprout-Less Herbicide Applicator was low compared with a separate herbicide treatment or a second treatment with brush saws. However, the efficacy of its use must ultimately be judged on the treatment's ability to control resprouting; FERIC did not assess this factor.

DISCLAIMER: This report is published solely to disseminate information to FERIC's members. It is not intended as an endorsement or approval by FERIC of any product or service to the exclusion of others that may be suitable.