May 2011 has been one of those wet starts to the growing season. Wet and warm weather provides good disease growing conditions. Disease pressure makes for poor spring cereal yields and grain quality.
Is Fungicide Always Warranted?
The question is, “when are fungicides warranted on spring cereals?” Timing application to the crop stage impacts the effectiveness of fungicides to suppress disease pressure, whether it is leaf, stem or grain disease. If the weather turns dry, fungicides may not be needed. It is always important to consider the weather conditions and potential disease pressure at the time of application.
Figure 1. 4 Leaf Ceral Stage (Zadock’s 14)
Another question is, “with the wet weather this May, should an earlier application of fungicide be applied?” From past research and on-farm trials, the use of a fungicide for leaf diseases when there is disease pressure present at weed control timing (or when the cereals are in the 4 – 5 leaf stage), has shown only about a 1 – 2 bushel per acre yield increase.
Leaf Diseases at Flag-Leaf Emerged Stage
For oats and barley, the greatest yield response from leaf disease control is when the fungicides are applied at the flag leaf emerged stage. This stage is when the last leaf emerges from the stem before the head emerges (Figure 2).
Figure 2. Flag-Leaf Emerged Cereal Stage (Zadock’s 37)
Crown Rust in Oats
In southern Ontario, oats need to have a fungicide applied at flag-leaf emerged stage (Zadock 37) for leaf diseases such as crown rust. Leaf diseases can be very devastating to both yield and quality, since the genetic tolerance of most of the oat varieties has broken down (Figure 3). In a 2008 oat fungicide trial in eastern Ontario, there was a 20% yield increase with the use of a fungicide at the flag-leaf stage on a variety where the genetic rust tolerance has broken down.
In northern Ontario, leaf diseases are less frequently an issue. However, growers should scout their fields as the oats approach the flag-leaf emerged stage, monitor the progression of the disease in southern areas and be prepared to apply a fungicide if conditions are favourable for leaf disease development.
Figure 3. 2008 Fungicide Trial on Oats – Note lodging in unsprayed strips
Fungicide Products For Leaf Diseases
There are several fungicide products available for control of leaf diseases in cereals. Tilt 250E, Bumper 418 EC, Stratego 250 EC, and Headline EC can be used for crown (leaf) rust. For other diseases such as leaf blotch, Quilt can also be applied. The retail price of the fungicides ranges from $9 to $14 per acre plus application costs.
Fusarium Head Blight
For fusarium head blight (FHB) suppression, fungicides such as Prosaro and Caramaba are most effective if applied when the cereal is at the 20% flowering stage (Figure 4 – the beginning of flowering in wheat) and proper nozzles are used.
The proper nozzle setup is the Turbo FloodJet, – alternating forward and backward nozzles to target the fungicide on both sides of the cereal head (Figure 5). On-farm trials have shown a 4 to 8 bushel per acre grain yield advantage and about a 30 – 50% reduction in the percentage of fusarium damaged kernels (%FDK).
Figure 4. Beginning of Flowering Stage of a Wheat Head – note pollen sacks
Figure 5. Turbo Floodjet – alternating forward and backward nozzle set-up for fungicide application for FHB suppression