New and Revised Disease Fact Sheets

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A new UW Extension disease fact sheet on Aphanomyces root rot has recently been developed and ready for download.  The fact sheet describes symptoms of Aphanomyces root rot, gives details about the pathogen that causes the disease, and gives some management ideas. You can download the fact sheet by visiting the ‘Fact Sheet’ section of the UW-Madison Field Crops Pathology website or CLICK HERE.

Revisions to fact sheets describing symptoms and management of Ergot of small grains and Fusarium head blight of wheat are also now available for download. To access these fact sheet, visit the ‘Fact Sheet’ section of the Field Crops Pathology website or CLICK HERE FOR THE ERGOT FACT SHEET or CLICK HERE FOR THE FUSARIUM HEAD BLIGHT FACT SHEET.

Wisconsin Winter Wheat Disease Update – June 24, 2014

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Figure 1. FHB Risk Map for June 24, 2014

Figure 1. FHB Risk Map for June 24, 2014

Damon L. Smith – Extension Field Crops Pathologist, University of Wisconsin

I have spent the last several days rating winter wheat variety trials and fungicide trials at the Arlington Agricultural Research Station in Arlington, Wisconsin, Columbia Co.  Wheat in this area is mostly in the mid-to-late milk stage.

Leaf rust was observed at low levels in border rows and plots not sprayed with fungicide.  Incidence (number of plants with symptoms) in some plots is near 50%.  However, severity (area of leaf covered by rust pustules) on flag leaves is low at 5% or less.  At this stage impact on yield by leaf rust will likely be low and fungicide sprays to control the disease at this stage are NOT recommended.

Septoria/Stagopsora leaf blotch was also observed on lower leaves of most plots.  Very few plots had leaf blotch symptoms on the flag leaves, and if they did, severity was in the 5% range. Impact on yield by leaf blotch at this location will be low.  Again, fungicides are NOT recommended on winter wheat at this growth stage.

Very little Fusarium head blight (scab) has been observed on winter wheat from Arlington, Wisconsin on up through to Chilton, Wisconsin. Currently the Fusarium Head Blight Prediction Center (http://www.wheatscab.psu.edu) is predicting moderate to high risk for head blight for much of the state of Wisconsin (Fig. 1).  Winter wheat in much of the state is likely past flowering now, and thus the window of opportunity to treat for head blight has passed. However, some late-planted barley may be emerging from the boot at this time and this is the window of opportunity to control scab on barley, especially with the risk being moderate to high.

If a fungicide is warranted for control of scab on barley, products such Prosaro, Caramba, or similar that contain triazole active ingredients can offer suppression of scab and reduce deoxynivalenol (DON) accumulation in harvested grain.  These products should be applied within a week from the beginning of flowering for reasonable control.  Products containing strobilurin fungicides should be avoided after heading.  Research has demonstrated that levels of DON can be higher after treatment with strobilurin products after heading.

Wisconsin Winter Wheat Disease Update – June 19, 2014

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Damon L. Smith – Extension Field Crops Pathologist, University of Wisconsin

I have scouted winter wheat fields and variety trials from Arlington Wisconsin up through Chilton Wisconsin this week, between rain showers.  Wheat in these areas is nearly finished flowering.  The window of opportunity to spray fungicides in these areas to control Fusarium head blight (scab) in winter wheat has now passed.

Figure 1. FHB Prediction Center Risk Assessment for June 19.

Figure 1. FHB Prediction Center Risk Assessment for June 19.

Currently the Fusarium Head Blight Prediction Center (http://www.wheatscab.psu.edu) is predicting moderate to high risk for head blight for the Door county peninsula and areas immediately adjacent to Green Bay (Fig. 1).  Winter wheat that is currently flowering in this area of the state is at high risk for infection by the fungus that causes scab. The prediction center is currently predicting low levels of scab in other parts of the state. This should be monitored closely by growers with barley. Some late-planted barley will be emerging from the boot soon and this is the window of opportunity to control scab if conditions are conducive.  With all the rain and warm temperatures across the state this week, I would suspect that the risk for scab on barley and any remaining flowering winter wheat will be elevated this weekend across much of the state.

If a fungicide is warranted for control of scab on winter wheat in the Door County area or barley, products such Prosaro, Caramba, or similar that contain triazole active ingredients can offer suppression of scab and reduce deoxynivalenol (DON) accumulation in harvested grain.  These products should be applied within a week from the beginning of flowering for reasonable control.  Products containing strobilurin fungicides should be avoided on wheat that has headed.  Research has demonstrated that levels of DON can be higher after treatment with strobilurin products after heading.

Figure 2. Cephalosporium Stripe symptoms on Winter Wheat.

Figure 2. Cephalosporium Stripe symptoms on Winter Wheat.

While scouting winter wheat fields at University of Wisconsin variety trials in the southern and eastern part of Wisconsin this week, I observed no rust or powdery mildew.  Trace levels of barley yellow dwarf were noted at all locations. At the Fond du Lac variety trial, high levels of Cephalosporium stripe (Fig. 2) were noted on certain varieties.  This location has seen short rotations between wheat crops, likely contributing to this epidemic.  We also noted high incidence (90%) of bacterial leaf blight on several varieties at this location. Some bacterial leaf streak was also observed, but incidence was less than 10%. Very low levels of Stagnospora/Septoria leaf blotch were noted. Most varieties had just completed flowering at this location and no scab was observed as of yet.

At the Chilton Variety trial, diseases are nearly absent.  The only disease noted on several varieties was bacterial mosaic at low incidence (<5%).  Cereal leaf beetle damage was moderate across many varieties in this trial.  Larvae were also found on flag leaves, but levels were below the economic threshold as of Tuesday.  Again at this location, most varieties had just completed flowering and no scab was observed as of yet.

Wisconsin Winter Wheat Disease Update – June 2, 2014

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FHB Update for Wisconsin - June 2, 2014

FHB Update for Wisconsin – June 2, 2014

Damon L. Smith – Extension Field Crops Pathologist, University of Wisconsin

Winter wheat in the southern portion of Wisconsin is at, or past, the flag leaf stage of growth. Disease reports have been few and far between this year.  This is because wheat looks very healthy. No diseases where observed on the wheat I inspected this weekend. Septoria leaf blotch I had observed very early this season has subsided and cannot be found now.  No powdery mildew was observed in these fields.  However, there have been several reports of very minor powdery mildew on wheat near the Janesville area.  Weather conditions have been very conducive for powdery mildew, so continue to scout for this disease.  If powdery mildew is observed at high levels of severity on flag leaves, then a fungicide application might be warranted.

No wheat rusts have been observed in the fields I have scouted this season.  I have received no reports of rusts on wheat in Wisconsin either.

In the next week or two, much of the wheat in Southern Wisconsin will be heading and flowering.  This is a critical time to control Fusarium head blight (scab).  If conditions are wet and warm during the flowering (anthesis) period, the risk for scab will be higher.  To assist in making decisions about scab management, consult the Fusarium Head Blight Prediction Center at http://www.wheatscab.psu.edu.  Currently, the risk for scab is low in most of the state.  However, as temperatures get warmer and if it continues to rain, the risk can increase quickly.

If a fungicide is warranted for control of scab, products such Prosaro, Caramba, or similar that contain triazole active ingredients can offer suppression of scab and reduce deoxynivalenol (DON) accumulation in harvested grain.  These products should be applied within a week or so of the beginning of flowering for reasonable control.  Products containing strobilurin fungicides should be avoided on wheat that has headed.  Research has demonstrated that levels of DON can be higher after treatment with strobilurin products after heading.

Continue to scout wheat regularly over the next couple of weeks.  This will be a critical time to make in-season disease management decisions.