While cool weather conditions over the last few weeks have worked to slow wheat down considerably, the development of the crop is still at least a week or two ahead of what is considered to be normal in Ohio at this time of year, according to an Ohio State University Extension wheat researcher.
Current growth stages range from Feekes 6, jointing, to Feekes 8, flag leaf emergence, says Pierce Paul, who is also a plant pathologist with the Ohio Agricultural Research and Development Center.
But, the difference between growth stages cannot be determined by looking at the height of the crop from the road, since relatively low temperatures and dry conditions may have prevented some varieties from reaching the height that is expected when the crop is between Feekes GS 6 and 8, he said.
"Short-looking wheat does not mean that the crop is not developing and advancing through the different growth stages," Paul says. "Growers who rely on the height of the crop as an indicator of crop development may miss Feekes GS 6, a critical growth stage for herbicide application, and Feekes 8, a critical stage for managing foliar diseases with fungicides."
Instead, growers need to walk their fields, pull tillers from multiple places, remove the lower leaves, and examine these tillers for the presence of nodes and the emergence of the flag leaf, Paul says.
"At Feekes 6, the first node is visible at the base of the stem, about an inch or so above the soil line; at Feekes 7, two nodes are visible, one about 2 inches above the soil line and the other about 3-4 inches above the first; and at Feekes 8, in addition to the two nodes seen at Feekes 7, the tip of the flag leaf, the fourth leaf above the first node, is visible," he says.
When fields reach Feekes 8, growers should start scouting their fields to see if disease is present and if so, how much, he said.
"Septoria blotch is typically one of the first to show up, and it already has been reported in some fields," Paul says. "This disease is favored by cool (50-68 F), rainy conditions, and although it usually develops early in the season, it really does not cause yield loss unless it reaches and damages the flag leaf before grain fill is complete.
"Like many other foliar diseases such as Stagonospora, Septoria reduces grain fill and the size of the grain."
Paul recommends that growers apply a foliar fungicide application at or after flag leaf emergence, noting that the greatest benefits occur when applications are made between Feekes 8 and 10.
This is largely because most major foliar diseases usually develop and reach the flag leaf after Feekes 8-9, he says.
Growers have several choices in fungicides available for use on wheat, including:
- If powdery mildew is the target disease, then Tilt or PropiMax should be applied.
- Tilt, PropiMax, Quadris, Quilt, Stratego, and Headline have good efficacy against Stagonospora leaf blotch, other leaf blotch diseases and leaf rust.
Growers should get current pricing of fungicides to determine their most economical control option, Paul says.
"Use 20 gallons of water per acre with ground equipment and 5 gallons of water per acre if applying by airplane," he says. "Using less water will lower effectiveness. Check labels for application timing restrictions."
For more on wheat fungicides, go to www.oardc.ohio-state.edu/ohiofieldcropdisease/images/NCERA_184_Wheat_fungicide_chart_2009_v22_modified.pdf