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While most of the winter wheat crop is past flowering in many parts of the state, we are continuing to monitor the Fusarium head blight risk especially for later maturing wheat or spring wheat in the state. Today’s risk map has shown a change in the risk of infection in pockets of state since we have seen heavier rainfall amounts the past week in many areas. There are several pockets that are in the medium to high risk of infection but it is important to pay close attention to the wheat growth stage regarding fungicide applications (see previous postings and also the Wisconsin Crop Manager for further information).

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.

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

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.