By Bayer CropScience
by Troy Basaraba, market development specialist
When it comes to disease protection in cereal crops, spraying a fungicide is a key component of an integrated pest management strategy. However, there are a lot of questions out there on when is the best time to spray. Seven years of field scale replicated research has indicated that waiting until head-timing to apply a fungicide on wheat and barley provides the best opportunity for maximizing both yield and crop quality.
The general rule of thumb has been, protect the flag leaf and you protect the yield, protect the head and you protect the quality. Since 2008, Bayer CropScience has been conducting field scale replicated trials on wheat and barley to determine the effects of fungicides where they looked at different fungicides as well as application timings. Averaged over seven years, many products and application timings provided a strong yield response, and an overall positive return on investment. However, fungicides applied at head timing on average out-yielded flag leaf applications and provided more opportunity for improved crop quality. Further to this, in trials where Folicur EW and Prosaro were applied at both flag leaf and head timing, the head timing averaged +0.7 and +1.8 bushels more per acre respectively. It has also been shown that by applying at the head timing an improved grade was seen 25 per cent of the time relative to the untreated. In order to maximize results at the head timing, growers have a short window of time for an optimally timed application. The question then becomes how to recognize that window.
First and foremost, it's important to understand the overall situation the crop is in. Different varieties will have different genetic disease resistance packages so knowing this will help growers understand the impact of disease on their crop if/when it appears. Cultural practices like crop rotation can have a huge impact on level of disease and tight rotations may set up for high disease levels. It is also important to be cognizant of what diseases have been present on their operation or in the local area in the past as this may indicate what may be coming in the future. For example, Fusarium Head Blight (FHB) has been a common problem for Ontario, Quebec and the Eastern Prairies for several years but it continues to migrate west and is becoming the new reality for growers in Saskatchewan and Alberta.
Secondly it is important for growers to constantly monitor and scout their fields. Keeping a constant eye on the crop is the best way for growers to identify the early warning signs of leaf diseases. How thick is the crop canopy? Are there weather conditions conducive for disease development? Is disease present in the area or moving in? Cereal crop pathogens are widespread in the prairies so if there are the right environmental conditions the pathogen will infect the crop.
Leaf diseases like rust, tan spot and septoria can infect the crop early in the season and can be detected by early scouting. However, given the right environment, leaf disease will continue to progress up the plant and infect newly formed leaves including the flag leaf. Predicting FHB infection is even more difficult as once you see FHB symptoms it is too late to protect the crop with a fungicide application. A preventative application is needed to provide any protection against this disease.
The typical fungicide spraying window spans from flag leaf emergence to full flowering. However the optimal spray timing to maximize both yield and quality in wheat is when the head has elongated from the flag leaf and the first flowers have emerged (see image at left). Fungicides applied at head timing (on average about 10 days after flag leaf timing) protect the head from diseases such as FHB and septoria glume blotch but also provide leaf disease protection. Fungicides applied at the flag leaf timing provide a protective barrier to leaf disease but offer no protection from FHB.
At flag leaf timing, growers should assess the level of leaf disease present and then decide if they can wait until head-timing to apply a registered fungicide and get protection from both leaf and head diseases with just one application. If disease levels are relatively low on the flag leaf there will likely be a window where growers can wait and spray at head timing and receive a dual benefit from their fungicide.
The optimal (but not complete) head timing window of application does not last long so if growers are expecting inclement weather or they don't think they can cover all their acres in that limited time be assured that if an application needs to go on a little later or earlier a clear yield benefit is still seen.
To summarize, it's important to scout and keep abreast of your crop condition and crop conditions in your local area. Seven years and 185 Bayer CropScience replicated trial results have proven that fungicides are a very effective aspect of disease management and applying at head timing has proven to provide growers the best bang for their buck by maximizing both yield and crop quality.
For more information on the research and how to maximize fungicide treatments visit www.itpaystospray.ca.