Evaluating Commercially Available Technologies for Weed Management in Blueberries: Saturated Steam and Rotary Brush

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Marcelo Moretti
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Organic growers often list weed control as their most difficult and time-consuming activity. Many blueberry growers still rely on hand-weeding, but labor shortages and higher costs make this practice less viable. The objectives of this research were: (1) to evaluate commercially available equipment such as saturated steam and a brush weeder, and two organic herbicides caprylic acid plus capric acid, and ammonium nonanoate; and (2) to examine the efficacy and crop safety of saturated steam as an alternative to hand-weeding to manage weeds growing at the base of blueberry plants.

More than three years of field studies have confirmed that both steam and the brush weeder are effective options to manage weeds, providing up to 95% weed control. Both tools can control weeds at costs calculated between $32 and $50 per acre per operation, requiring only a driver as labor. However, the poor reliability and slow operation capacity of these equipment on the large scale indicates that they are not acceptable options within commercial systems. The study on hand-weeding alternatives indicated that saturated steam is effective in controlling field bindweed and other weeds growing at the base of the blueberry plants. Steam applications were made using a hand-held applicator, and assessments of the long-term crop impact of multiple applications of steam are ongoing. This two-year study indicates that steam is safe for use near new blueberry shoots when applied at the rate of 730 gallons of saturated steam per acre or less, equivalent to a driving speed of 0.5 mph. Organic herbicides were also compared for this use. Our results indicate inadequate efficacy and crop safety of these chemical tools. Steam has the potential to replace hand-weeding, but further development of tractor-mounted steam applicators able to stand up to use under commercial applications use may improve performance. The poor reliability of the current equipment configuration coupled with lack of local technical support leads us not to recommend adoption of this technology at this time.

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