Early Season Wheat Disease Assessments
Updated: 15 May
We have begun our early season wheat disease assessments at the winter wheat variety trials in Wisconsin. Our approach for disease assessments follows the recommendations we made in the March 26, 2009 Wisconsin Crop Manager article, entitled, “Do I Need to Spray a Foliar Fungicide in Wheat in 2009?” These assessments are also a part of the thesis research for Karen Lackermann, Plant Pathology, to improve the decision management system for controlling wheat diseases in Wisconsin.
At Janesville and Lancaster, wheat growth and development currently ranges from Feekes 4-5 (pseudostem erection; Zadoks 30) to Feekes 6 (1st detectable node; Zadoks 31). In our assessments at those two locations, we have found symptoms of the Septoria leaf blotch complex, leaf rust, and stripe rust. The level of disease is relatively low and specifically, we have only noted symptoms in the lower canopy and nothing on the newest emerged leaf. At this range of growth stages, we do not recommend the use of foliar fungicides for Septoria or the rust diseases. Scouting over the next two weeks, however, will help to determine if these diseases are increasing in the canopy. Furthermore, the use of the thresholds we outlined in our Wisconsin Crop Manager article can help determine the need for a foliar fungicide as we move into flag leaf emergence.
We have also completed our first assessments at the Chilton variety trial location. Wheat was at Feekes 4-5. Similar to the other locations, we observed Septoria leaf blotch, leaf rust, and stripe rust. Of all the samples we have assessed, only 1 had symptoms of leaf rust on the newest leaf. Our recommendation is similar to Janesville and Lancaster at the moment.
We will continue our assessments for the rest of the growing season including Feekes 7 (2nd detectable node; Zadoks 32), Feekes 8-9 (flag leaf emergence; Zadoks 37-38), and Feekes 10.51-11.1 (flowering to soft dough; Zadoks 60-75) at all of the variety trial locations and will continue to update you all on how wheat diseases are progressing around the state.
Verify Wheat Growth Stage Before Applying Growth Regulator Herbicides
Poor wheat stands caused by late planting, decreased tillering, and winterkill have many growers contemplating herbicides in 2009. Make sure you properly growth stage your wheat before applying dicamba or 2,4-D. The mid September and early October planted wheat crop is at or nearing the Feekes 4-5 or Zadoks 30 growth stage (pseudostem erection or hollow stem) (Image 1.). After this stage and when wheat has a visible joint (Feekes 6), wheat can be very sensitive to dicamba and 2,4-D herbicides. Last year we had several reports of 80 bushel wheat dropping to 20 bushel wheat when dicamba was applied at Feekes 6. After jointing there are several other herbicides that can be safely used. Please refer to Pest Management in WI Field Crops Bulletin A3646 for these options.
Image 1. Feekes 4-5 or Zadoks 30 growth stage in wheat
Chris Boerboom
A New Feature – Weather Updates from Winter Wheat Variety Trials
During the winter period, we were able to purchase four new weather stations for use at the winter wheat variety trial locations. To help provide information from those weather stations to growers, we will posting on a near-weekly basis graphs for temperature, relative humidity, and rainfall. We hope you find these useful.
PERIOD: 26 APRIL TO 2 MAY 2009
Location: Arlington
Location: Chilton
Location: Janesville
Location: Lancaster
Small Grain Aphids Have Arrived, but at Extremely Low Numbers
I scouted our winter wheat planting date by barley yellow dwarf virus trial this morning at Lancaster WI. Our earliest planting date (September 17th 2008) survived the winter very well and is nearing the Zadoks 30 (pseudostem erection) growth stage. Crop development of the later planting dates (September 30th and October 13th) are significantly behind the earliest date, Zadoks 13, 22 and 12, respectively. Across all of our plots I found only one Oat Bird Cherry aphid. The established spring threshold for this pest is 50 aphids per linear foot of row.
Oat Bird Cherry Aphid
Drawing Courtesey of Dennis Murphy Wheat Fusarium Head Blight Prediction Center – 2009
The Wheat Fusarium Head Blight Prediction Center and forecast tool is now active for 2009. The site can be accessed at http://www.wheatscab.psu.edu/. I will again be writing state commentary for this site and will update growers on wheat growth stages in relation to our observations of wheat diseases. We will have an active wheat program for 2009, with our disease assessments commencing at Zadoks 30 (Feekes 4-5, or jointing) and continuing through our head blight assessments at approximately soft dough. We recently wrote for the Wisconsin Crop Manager an updated article on making foliar fungicide decisions based on current knowledge of disease thresholds for diseases like rust, powdery mildew, and Septoria leaf blotch. That is available here.
WSMB Offers Free Soybean Cyst Nematode Testing
Shawn Conley, Paul Esker, and John Gaska
The UW-Madison Agronomy Department, in cooperation with the Wisconsin Soybean Marketing Board, is again offering free soybean cyst nematode (SCN) soil testing for Wisconsin growers. This program is intended for growers to sample several of their fields in order to identify if SCN is present and at what levels. Growers will be responsible for collecting soil from fields suspected to have SCN and then sending the sample to the SCN testing laboratory for analysis. They will receive a lab report back with the SCN egg count and a brochure to help plan future rotations and other cultural practices to lower SCN infestation if they exist.
We have a limited number of these free kits available and will furnish them on a first come – first served basis at up to four per farm. Crop consultants, advisors, and crop input retailers are encouraged to request kits for their client’s farms. Each kit has a bag and a prepaid mailer for one soil sample, which should represent about 10-15 acres. Both the postage and lab fees are prepaid. Anytime before, during, or right after the growing season are great times to collect soil samples for routine soil fertility analysis and for SCN monitoring.
Soil sample test kits are available now and can be requested from Colleen Smith at clsmith8@wisc.edu or at 608-262-7702.
For more information on SCN testing and management practices to help reduce the losses from this pest, please contact: Shawn Conley: spconley@wisc.edu; 608-262-7975
Summary – 2009 Winter Wheat Workshops
The first ever Winter Wheat Workshops were recently completed in Wisconsin. We wanted to take this opportunity to thank all of the participants who attended the workshops. We also want to thank our industry sponsors (Partners in Production and Syngenta), as well as Jim Stute (UW-Extension Rock County), Mike Rankin (UW-Extension Fond du Lac County), and Mike Ballweg (UW-Extension Sheboygan County) for being host sites. Based on feedback from participants, we do plan to offer workshops again in 2010 and we will keep you posted on dates and times at a later date. Also, based on requests from participants, we are making available here copies of the slides from the talks (posted in PDF format).
Understanding Wheat Growth and Development and Wheat N Management Decisions
Disease Diagnostics and Foliar Fungicides
Should You or Shouldn’t You – Bin Run Seed?
For further information regarding agronomic, entomological, or plant pathological information pertaining to wheat, please consult our respective websites:
“CoolBean.Info”: http://coolbean.info
“Field Crop Pathology”: http://www.uwex.edu/ces/croppathology
“Field and Forage Crop Entomology”: http://www.entomology.wisc.edu/cullenlab
