Evaluation of the tolerance of lowbush blueberry to pine oil used in weed management

Project Code BPR13-030

Project Lead

Jim Jotcham  Marbicon Incorporated, Nova Scotia, Canada

Objective

To develop crop tolerance data and determine the optimal timing of applications in support of a regulatory submission for AEF-1201 (pine oil) for weed management in lowbush blueberry production

Summary of Results

Background

Lowbush blueberry is a native perennial crop in Canada and grows in low pH soils without associated tillage or cultivation. Weeds thrive in this habitat if not controlled, and can shade and compete with the crop for nutrition, reduce yield and quality and can interfere with harvesting. Therefore, weeds are a major concern in lowbush blueberry production in Canada. There are limited products available currently for weed management in lowbush blueberry production and growers have need of reduced-risk herbicides to manage weeds in organic and conventional production systems.

At the 2012 Biopesticides Priority Setting workshop, AEF-1201 (pine oil) was selected as a potential priority solution for the management of weeds in lowbush blueberry. AEF-1201 is a non-selective biological herbicide, developed by AEF Global, Canada. The active ingredient in this product is pine oil, registered in New Zealand and Australia for weed control on certain horticultural and orchard crops. There is ample evidence and data indicating the efficacy of the product against a number of weed species, so this project aimed to test crop tolerance to the product in both the sprout and crop years of lowbush blueberry production, and to determine the optimal timing of applications of the product.

Approaches

Two tolerance trials were conducted during 2013 in Nova Scotia. Because lowbush blueberries are grown as a biennial cropping system, with a sprout or vegetative year alternating with a crop or fruiting year, one trial was conducted in the spring of the sprout year to treat the crop plants before new blueberry sprout emergence; and another involved treatments of lowbush blueberry plants during the crop year, before bloom and after bloom. Two application rates, 20 per cent (%) and 40% volume per volume (v/v), were used for plant treatments in two trials. The crop tolerance was assessed by measures of the percent cover of blueberry plants in a square metre quadrant placed in the centre of each plot. A total of 10 stems were sampled from each plot to record numbers of flower and leaf buds per stem and measure stem length. Phytotoxicity was assessed with a visual scale from 0 to 100 %, where 0 is no visible injury and 100% is completely brown. In addition, blueberry yield was tested for the trial in the crop year.

Results

In the trial of sprout year, the data showed that neither the low (20%) nor the high (40%) rate produced a difference in percent plant cover in plots when compared to the untreated controls. Neither rate resulted in differences in numbers of flower and leaf buds on the stems and stem length when compared with the untreated control. No phytotoxicity was observed in lowbush blueberry plants treated during the sprout year, except for a slight delay in plant cover development in some plots treated with the high rate of pine oil, however plant cover was not impacted at a later growth stage.

In the trial conducted during the crop year, obvious signs of phytotoxicity were observed one week after both pre-bloom and post-bloom applications. Up to 70% of leaves were damaged a week after treatment with two rates of pine oil in the pre-bloom treatments. Both rates significantly reduced yield in pre- and post-bloom treatments. Overall, data from these trials showed that the pre-bloom treatments with pine oil posed much more serious leaf damage and worse effect on yield than those treated after bloom. In addition, the leaf damage and yield loss were higher with increased in the concentration of pine oil.

Conclusions

Trial data showed that lowbush blueberries are tolerant to early spring applications of pine oil in the sprout year, and that the product could be used in early spring, before leaf bud break to manage the weeds at the early growth stage. In addition, pine oil can be applied as a spot treatment in lowbush blueberry field regardless of the growth stage of the crop, provided care is taken to avoid the crop.

There was very significant yield reduction caused by serious phytoxicity when the product was directly sprayed onto lowbush blueberry plants during the crop year, suggesting that the foliar application is not feasible during the crop year.

The product is currently under regulatory review for this use in Canada.

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