Weed Wiper


Weed Wiper Evaluation For Drainage Ditch Brush Control

J. Kemble, D. Belt, M. Vangessel, P. Krishnan and K. Henning

During the summer and fall of 1996 a preliminary study to chemically control vegetation on tax ditch slopes and horizontal areas by environmental friendly means was funded by the Department of Natural Resources and Environmental Control Division of Fish and Wildlife, First State Resource Conservation and Development Council Inc. and Kent and Sussex County Conservation Districts. The University of Delaware, Bioresources Engineering Department was responsible for designing and field testing the application equipment. The concept was to wipe targeted tall growing woody vegetation with herbicides leaving low growing vegetation to maintain stability on the horizontal and slope areas of the tax ditch. This approach also worked well as a way to provide wildlife habitat and filter zones. The preliminary results were so promising that an expanded study was suggested by the Department of Natural Resources and Environmental Control. Beginning June 1, 1997 work began on a pilot program with support coming through the Kent and Sussex Conservation Districts. With the success achieved using the wiper approach, on July 1, 1999, Kent and Sussex Conservation Districts implemented a cost share program for the tax ditch districts. This now made the unit available to ditch managers as an alternative to continuous mowing.

The initial testing in 1996 started with a 10 foot long side applicator for the ditch slopes and a 10 foot front width for treating the horizontal area. The applicator surface was a rough carpet material attached to an aluminum channel. A distribution tube released the herbicide onto the applicator surface. The actual application was .4 gallon per acre when driving the equipment at 1.7 miles per hour. The carpet unit worked well in controlling vegetation but did not hold up well in heavy aggressive brush.

A second set of applicators was installed in the early fall of 1997 which utilized industrial grit abrasive bonded to an aluminum channel. A redesigned distributor tube, a front edge scrapper and a wiper brush were other features included in the new unit. This unit proved to be very durable and currently has performed application on 2,400 plus acres on a 12 month treatment schedule.

To date the wiper unit has performed over 600 miles of treated area on tax ditches involving a variety of plants and varying degrees of vegetation growth. At this point in the research some observations can be drawn based on the units performance criteria. The evaluation of the effectiveness of the unit to control vegetation takes into consideration; type of applicator, season, herbicide type and rate, type and age of vegetation, and cost of application. The following preliminary results can be presented based on the previous considerations; the grit bar is durable and performs well, early summer to late fall applications are most effective, winter and early spring applications show promise because of secondary disease effects, .2 to .3 gallons per acre of a 20:1 glyphosate to arsenal mix is effective, Sweetgum, Cherry, Tulip popular, Sumac, Oak, Birch, Devils walking stick, and Maple have been controlled to 90% or greater with one application. Black locus and Pines show slow response and usually require a retreat the following year, I to 3 year growth is desirable however 4 year growth has been treated successfully, a second treatment two years after initial treatment is usually needed to spot treat, the acre cost of chemicals at .2 gallons per acre is $8.42, with tractor and wiper unit depreciation, replacement parts, fuel service, herbicides, safety equipment, transporting costs, labor, administrative and overhead for commercial application the cost per acre at the .2 application rate is $34.00.

Initial cost figures comparing the weed wiping concept to other methods have demonstrated cost savings with the wiper approach. Current costs at $34.00 per acre for wiping one mile of ditch 30 feet wide on each side equals $247.18 at the .2 gallon per acre application rate. Increasing the application rate to .3 gallon per acre, results in a total of $284.00 per mile. Broadcast spraying costs, for just herbicides, to treat the same area can exceed $500.00. Cost alone for broadcast spraying is not only prohibitive but total eradication of vegetation along the ditch is not desirable. Mowing is currently being performed on I or 2 year cycles. For the same width as wiping or less, mowing costs are averaging $300.00 to $350.00 per mile of ditch. Some areas are as low as $275.00 and others go as high as $500.00. Vegetation growth and accessibility are partly responsible for the range in mowing prices. Because of the application concept being utilized with the wiper unit, cost variation per mile of ditch is minimized.

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