This summer the West Nipissing/East Sudbury Soil and Crop Improvement Association and the Northern Ontario Farm Innovation Alliance carried out a research project testing Priaxor, a fungicide designed to protect alfalfa against a range of fungal diseases. This trial was specifically aimed at Leptosphaerulina trifolii, which is the fungi that causes a disease called lepto leaf spot.

Lepto leaf spot results in the appearance of small black or brown spots on the leaves of alfalfa, which can reduce the plant’s ability to photosynthesize and can result in leaf death. Lepto is more prevalent in cooler, damper soils.

The trials were conducted by Ben Schapelhouman of TECC Ag at two sites in West Nipissing. Ben has seen lepto leaf spot in his work across the northeast, including at sites in the Timmins, Earlton, and Verner areas. Priaxor was released in 2014, and this is the first formal trial for it in northern Ontario.

In this trial, strips of untreated alfalfa and alfalfa treated with Priaxor were alternated so that a total of 1.87 acres of each were grown. At the first site, Priaxor was applied on May 2, 2021, and the alfalfa was harvested June 8. Yield was measured by baling, wrapping, and weighing the alfalfa and then comparing the weights of the Priaxor-treated alfalfa and the untreated alfalfa.

The treated alfalfa at the first site yielded 2.24 metric tonnes of dry matter, while the untreated alfalfa yielded 1.84 metric tonnes. Assuming a price of $200 per metric tonne and accounting for the Priaxor application cost of $27 per acre, the treated strips resulted in a net income of $382.37 per acre while the untreated fields accounted for $353.90 per acre. This is a $28.47 per acre increase in revenue in the treated strips.

Ben reported very few visible symptoms of lepto leaf spot in either the treated or untreated alfalfa strips. Since Priaxor works preventatively and must be applied prior to the appearance of leaf spot symptoms there’s always the possibility that the treated field would not have developed Lepto leaf spot regardless. The results of this first trial would seem to suggest that there are few downside risks to applying Priaxor, even if it turns out to be ultimately unnecessary.

The data from the second location is not yet available, but it will be interesting to see whether or not it corresponds to the results from the first location.

This trial was funded in part by an OSCIA Tier 1 grant. Tier 1 is the $1500 discretionary grant that is available to all local Soil and Crop Improvement Associations. If you have an idea for a research project, contact your local association secretary or NOFIA at or 705-647-4782.

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