Objectives
The objective of this project was to demonstrate the response of flax to various seed-applied and foliar fungicide options with a focus on establishment, maturity, and yield.
Project Description
Although conditions were not ideal for the purposes of this project, these results were not inconsistent with previous research and demonstrations.
Focusing on seed treatments, past results have been variable with a fairly large percentage of trials showing no measurable benefit but increases in plant populations and, to lesser extent higher yields, occasionally occurring. It can be difficult to predict whether responses will occur but typically seed treatments are most likely to be beneficial when the seed source is contaminated with the pathogen being controlled or under stressful conditions at seeding. Examples of stressful seeding conditions might include cold, waterlogged soils or potentially very dry soils where emergence might not occur for extended periods and/or initial growth is likely to be poor. In the current project, a response (both plant populations and yield) occurred 20% of the time, or at one out of five locations. Other cases where growers should consider using a seed treatment would be when the disease (or insect) being managed has been problematic in the field or region in previous years. Otherwise, with clean seed, no known history of the pest, and normal seeding conditions, measurable benefits are relatively unlikely. It is worth noting, that the need for a seed treatment (and subsequent responses) may be variable across the landscape and, as such, difficult to detect in small plot trials. For example, there may be a greater need for a seed treatment in lower slope positions in wet years, particularly with crops that do not tolerate wet soils well and, as such, are stressed and susceptible to disease. While the response at Prince Albert was stronger with Insure Pulse, substantially more evidence would be required to say that this advantage is repeatable and applicable under a wide of conditions.
With regard to foliar fungicides, previous research and demonstration trials have shown strong responses when disease pressure is sufficiently high and a reasonably high frequency of response, especially through wetter periods. For example, from 2010 to 2016 at Indian Head, yield increases with Headline EC were detected 71% of the time five out of seven years) and provided an overall yield benefit of 10%, or 207 kg/ha (3.3 bu/ac) when averaged over this seven year period. However, there are also a large number of cases, including those in the current project, where disease pressure is low and there are no yield benefits or noticeable effects of fungicide on maturity detected. When noteworthy effects on maturity have occurred, they have always been accompanied by substantial yield increases. The recommendation, at least for wetter regions, would be to scout frequently starting just prior to bloom and through flowering and be prepared to apply a fungicide but only do so if the disease is present and conditions are conducive to further infection. A general recommendation is to apply fungicide about a week after the very first flowers are observed but later applications can be beneficial or even superior if conditions during flowering go from drier to wetter (do not apply outside of label recommended stage). Relative to many field crop diseases, pasmo is relatively easy to scout for as it progresses up the plant with precipitation and can still be managed after there are visible symptoms, unlike sclerotinia or fusarium head blight. Pasmo symptoms first appear on the bottom leaves, eventually moving to upper stems and even bolls if left unchecked and conditions are favorable for disease. In most cases disease will still be limited to leaves on the lower half of the plant at the time of fungicide application and, if it does not progress past this point, any impacts on yield will be negligible. In drier regions, such as Swift Current, flax yield responses to fungicide are unlikely but may occur in wet years; therefore, careful monitoring is still recommended. While crop rotation is certainly a factor to consider, disease can occur in fields where flax has not been grown in many years if the weather is conducive, thus scouting is still recommended under these circumstances as well. With no significant fungicide responses in the current project, no comment can be made on the relative performance of the two products evaluated (Headline EC versus Priaxor); however, utilizing products with multiple modes can help prevent the development of resistance to certain active ingredients and may also provide more complete disease control.
