Fusarium Head Blight Forecast - 27 May 2010

With the warmer than normal temperatures we have experienced the past week, the winter wheat crop is rapidly progressing. In some of our research trials, we are at full heading into early flowering and now is an important time to consider the risk for Fusarium head blight. As a follow up on my earlier posting from this week, the current risk for FHB around the state is (27 May 2010): low with some small pockets of medium to high risk (highest risk along the Lake Michigan shoreline)

Over the next 1 to 3 days, the forecast risk is low for Fusarium head blight. For those fields where the winter wheat crop is a little further behind, the critical period to monitor will most likely be in the next week or so. Continue to monitor the Fusarium Head Blight Prediction Center for the most up-to-date information.

Seed Treatment Choices for Growers Planting RR2Y Soybean in 2011

In a recent article published in Reuters, "Monsanto making changes amid farmer complaints" by Carey Gillam, Monsanto executive vice president Brett Begemann, indicated that growers will no longer be required to use seed treatments when planting RR2Y® soybean. This change in marketing strategy will effectively give growers the choice in 2011 to use no seed treatment, Monsanto's Acceleron™ seed treatment products or a competitors.

Looking Ahead - Early Scab Forecast and Fungicide Labels

Winter wheat in some areas of Wisconsin is starting to head (Feekes 10.1). With the warm weather we are currently experiencing, it is expected that the wheat crop will remain ahead of 2009 conditions and that we should soon seen evidence of flowering in portions of the state. To better understand the flowering growth stage, please check here for an UWEX You Tube Video by Shawn.

Additionally, I have begun to monitor more closely the forecast for Fusarium head scab and will be providing updates over the next few weeks, especially as we monitor our own studies for the current growth stages. In terms of our observations to date, powdery mildew is still the primary disease of note in the 2010 but there have been reports of Septoria leaf blotch, low levels of leaf and stripe rust, and some evidence of bacterial leaf diseases. The latter is one that we have few options for control (i.e., fungicides are not effective) at this point in the growing season.

In terms of Fusarium head scab risk as of today (May 24), it is low throughout the state and the risk remains low over the next one to three days.

As a reminder, paying attention to the wheat growth stage as we move into flowering is critical. Most commercial fungicide products are only labeled through Feekes 10.5 (full heading) and others have restrictions based on days to harvest. Below is a partial summary of many products and this can also be accessed here. Not all products may be listed and not all products (especially some generic forms of tebuconazole) may be approved in WI. It is important to always check the label for specific use requirements.

Restrictions based on growth stage of Feekes 10.5 = Quadris, Headline, Tilt, Propimax, Bumper, Twinline, Quilt, Quilt Xcel

Restrictions based on a 30 day PHI = Caramba, Proline, Prosaro, Tebuconazole products (e.g., Folicur)

Restrictions based on a 35 day PHI = Stratego

Plant height impact on wheat yield

As wheat begins to move into the flag leaf (Feekes 9) and boot (Feekes 10) growth stages many growers and consultants are commenting on the short stature of the 2010 wheat crop. We must first address the cause of the short wheat before we can assign yield estimates. Let's first address planting date. Late-planted wheat will generally be shorter than on-time planted wheat. The yield loss attributed to late-planted wheat is not merely a function of height but reduced tiller number and biomass capacity (planting date impact on wheat yield).

For our on-time planted wheat, development and in this case height is governed by many factors including water, temperature, as well as light quality and quantity. Data from our 2002-2007 winter wheat variety trials show only one year (2005) where there was a positive relationship between yield and plant height (Chart 1.). This suggests that height alone has no direct influence on wheat yield. As long as the minimum threshold for LAI (leaf area index) is reached wheat yield will then be determined by head number, head size, kernel number per spikelet, and kernel size. Since head number, head size, and kernel number per spikelet are already determined we are just waiting on the grain fill period to finalize our 2010 yield.

Chart 1. Relationship between plant height and grain yield.

Powdery Mildew Update

As noted in Shawn's previous posting, the wheat growth stage is mostly around Feekes 7. Karen Lackermann, graduate student in plant pathology, continues to collect disease data in the winter wheat variety trials and has been paying particular to the powdery mildew situation this year. The levels of powdery mildew have been variable across trial locations, with the highest disease incidence being observed at Chilton. Even within sites, there is high variation in disease incidence and severity. For example, at Chilton, some varieties have 0% incidence and severity, whereas other varieties have higher levels with severity ranging from 5 to 20% on the flag-3 (three leaves below the flag leaf). On the flag-2 leaf (two leaves below the flag leaf), severity has been moderate in these varieties, ranging from 1 to 5%. No symptoms of powdery mildew were observed on the flag-1 (one leaf below the flag leaf) leaf.

As we move into flag leaf emergence at Feekes 8, pay particular attention to symptom severity on the flag-2, flag-1, and flag leaf. If the average number of pustules on the flag-2 leaf and the leaves above it is 5 or greater, a foliar fungicide may be warranted for control of powdery mildew. If symptoms are only being observed in the lower canopy, below the flag-2 leaf, it may not be economic to apply a foliar fungicide.

Predicted Cold Temperatures Should not Impact Wheat

Cold temperatures (30 to 32 degrees F) are predicted across the state of WI for Friday and Saturday mornings. Our winter wheat plots at Arlington and Lancaster WI are arguably the most advanced in the state. Last night (5/5/10) the most advanced winter wheat varieties were in the late Feekes 7 (2-3 detectable nodes and just prior to flag leaf emergence) growth stage. Based on these grow stages the winter wheat crop should be safe down to 28 degrees F. For more detailed information please see "Know Your Wheat Growth Stage to Predict Cold Injury".

Fusarium Head Blight Alerts Available

If you are interested in receiving real-time alerts for Fusarium head blight updates or field reports, the U.S. Wheat & Barley Scab Initiative is offering a free subscription service in 2010. To sign up for these alerts, please click here. The alerts are a summary of commentary made by wheat disease specialists throughout the country as part of the Fusarium Head Blight Prediction Center. You can receive alerts in email and/or text message form. You can also sign up for different types of reports, whether just a national summary or specific regions. For example, if you just want to see a summary from Wisconsin and the corresponding soft winter wheat region, you should mark the "Mid West/Northern Region, Soft Winter Wheat".

If you have any questions about this service, please free to contact me.