Project Code: BPR12-010
Project Lead
Nancy Cain - Cain Vegetation Incorporated, Ontario
Jim Jotcham - Marbicon Incorporated, Nova Scotia
Objective
To develop efficacy and crop tolerance data in support of a regulatory submission for Munger Vinegar Plus for the management of sedges and rushes in cranberry
Summary of Results
Background
In Canada approximately 79,000 metric tonnes of cranberry are produced annually with a farm gate value of $73.5 million. The impact of weeds on cranberry yield and quality is of great concern to growers in Canada. In an effort to minimize herbicide risk and develop reduced-risk integrated pest management programs, Munger Horticultural Vinegar Plus (MHVP), developed by Munger Lawnscape Distribution Incorporated, was selected as the priority solution for the management of weeds in cranberry by growers at the 2011 Biopesticides Priority Setting Workshop.
MHVP (20% acetic acid) is a post emergent, foliar active, weed management product. The product is non-selective to green foliage and non-residual in soil. The active ingredient of MHVP, acetic acid, damages plant tissues and thus dries out the plant.
Approaches
Two field trials were conducted on sedges in cranberry bogs in Ontario and Nova Scotia in 2013. In the trials, MHVP was applied by foliar sprays at the rates of 3 and 6% volume per volume (v/v) or by soil injection at the rates of 6 and 9% (v/v). The application volume varied from 1500 to 2000 Litres per hectare (L/ha). Two applications were made on June 23 and July 31 in Ontario and June 6 and August 6 in Nova Scotia. Water was applied as the untreated control and Callisto (mesotrione) as the commercial standard, both at the same frequency as the test treatments.
MHVP was evaluated for efficacy by percent weed control with a 0 to 100% scale, where 0 represents no weed killed and 100% represents all weeds killed.
Phytotoxicity to the crop was measured visually by recording the percent necrosis/discoloration to the leaves and green tissue of treated cranberries for foliar spray application or the point of injection.
Results
Efficacy of MHVP was assessed weekly starting one week after the first treatment.
The trial data showed that the foliar and soil injection applications of MHVP provided varying levels of weed control in Nova Scotia and Ontario. In Nova Scotia, neither foliar nor soil injection applications performed well, reducing weeds by less than 30% in both cases. In Ontario, however, when sprayed at the rates of 3% and 6%, the product gave up to 65% and 50% control of sedge plants, respectively. The soil injection reduced weeds by 59-66% 3 weeks after the first injection and up to 97% of weeds after the second injection at the rate of 6%. Increased product rate provided greater efficacy. When injected at 9%, the product provided 71% of weed reduction by the first injection and 94% of weed reduction by the second injection at the end of trials.
Crop tolerance data from Nova Scotia and Ontario indicated that the rates of MHVP applied by foliar or injection into soil in the trials all caused significant localized injuries to cranberry plants compared to the untreated control. In general, localized crop injuries were increased with the increase in the MHVP rate. The significant injuries by foliar and soil injection applications reduced cranberry yields, with highest concentration resulting in greatest yield reduction.
Conclusions
MHVP provided significant efficacy for the suppression of sedge weeds by foliar and soil injection applications in cranberry; however both application methods caused significant injuries of cranberry plants, thus reducing the yield. Thus, the results of this study suggest MHVP should be used at 6% or soil injected at 9% only as a spot treatment for the control of sedges, avoiding contact with cranberry plants, including root systems. This use pattern would be appropriate for both conventional and organic farms for spot control of weeds. For new cranberry bogs, the product can be used for broadcast spray at high concentration rates to kill sedges prior to planting cranberries.