Jun
18

Head Scab Numbers in Putnam County

by Glen Arnold, Putnam County

I have evaluated wheat fields in Putnam County for head scab (Fusarium Head Blight). This disease can occur when we receive rainfall during the flowering period of the wheat crop.

I looked at 15 fields across the county earlier this week. The % of wheat heads showing some scab infection (ranging from a single kernel to the entire head) was 5.4%.  Generally, fields that flowered earliest and showed no evidence of having a fungicide applied, appear to have the most disease. The worst field had 28% of the heads showing infection while other fields had 1% or less of wheat heads showing infection.

 Most, but not all, of the fields I looked at did have a fungicide applied during the growing season for leaf diseases and a fungicide applied for head scab control.

As a reference, here are my head scab numbers for previous years of scouting.

 2010–29.3%

2009–2.5%

2008–10.0%

2007–0.8%

2006–9.4%

2005–0.4%

2004–7.7%

2003–1.0%

2002–1.6%

The earliest wheat varieties in Putnam County began to flower the week of May 24th.  We had rain on Tuesday, Wednesday, Thursday and Saturday that week totaling over 4.5 inches.  The 2011 head scab levels are considerably lower than what I expected to find given all the rain we had in May. This could be due to the use of head scab fungicides or the very dry early June weather.

Wheat in the northern part of the county generally flowered during the week following Memorial Day and benefitted from the dry weather. In 2010 we had excessive rainfall throughout June (planted soybeans right up to the start of the county fair) which seemed to add to the vomitoxin problem.

Another observation I wanted to pass along is that many wheat fields have suffered damage from the very wet April and May. The plants appear to be cannibalizing their leaves (flag leaves are brown but not diseased) in an effort to fill the head. This could be due to the roots dying or at least unable to uptake nutrients. Some fields may also have run out of nitrogen. I would expect lower test weights and poorer yields as a result.

Many local elevators were hoping for good quality wheat this year to blend with some of the poorer quality wheat they are holding from the 2010 crop. Receiving over six inches of rain in April and seven inches of rain in May has really hurt what had the potential to be a good wheat year.

Here are web sources for Fusarium Head Blight information.

 http://www.ces.purdue.edu/extmedia/BP/BP-33-W.pdf

 http://ohioline.osu.edu/ac-fact/0004.html

 http://www.wheatscab.psu.edu/PDF/Fusarium_Head_Blight_.pdf

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