The head scab disease is the same disease that caused the vomitoxin in the corn crop last year.  The combination of a very wet spring during the heading and blossoming period of wheat and high levels of inoculum from the 2009 corn crop; appear to have combined to create this problem.  The wheat crop in Paulding County began to flower in mid-May.  Weather data from the Paulding Reservoir recorded precipitation on 9 of the 15 days between May 10th and May 24th.

The earliest and most obvious symptom of head scab occurs soon after flowering.  Diseased spikelets turn light-straw colored and have a bleached appearance due to premature death of tissues.  Healthy spikelets on the same head retain their normal green color.  One or more spikelets may be infected, or the entire head may be diseased.  When the fungus infects the stem immediately below the head the entire head may die.

At this time, survey results from 73 fields in 16 Ohio counties have indicated the incidence of head scab has been found to be in the moderate to high range in 70% of the surveyed fields.  The incidence in fields surveyed ranges from 3 to 61%, and overall county averages range from 6 to 41%.  Of the fields surveyed, 30% had incidence less than 10 percent, 30% were between 10 and 25 percent, and 40% of the fields had higher than 25 percent incidence.  All of the fields with lower than 10 percent incidence were in the southern, southwestern, or northern part of the state.  Regions with less than 10% incidence may have escaped disease by flowering before or after the period of greatest risk.  The majority of fields with greater than 25 percent incidence are in the west-central and northwestern parts of the state.

Five wheat fields were surveyed in Paulding County.  The percent of heads showing some scab infection from a single spikelet to an entire head, ranged from 29.6% to 50.2%.  These fields were not treated with fungicide.  This survey was conducted in previous years and the results are as follows: 2009 – 4.8%, 2008 – 10.2%, and 2007 – 1.4%.

Head scab can result in vomitoxin in wheat.  The best strategy is to blow as many of the lightweight infected kernels out the rear of the combine as possible.  This could be a year similar to 1996 when vomitoxin was a widespread issue in the wheat crop. The occurrence of scab does not automatically mean that vomitoxin will be present.

The following are web sources for Fusarium Head Blight information: http://www.ces.purdue.edu/extmedia/BP/BP-33-W.pdf  and

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

Jim Lopshire, Extension Educator