20th Annual Illinois Wheat Tour

May 22, 2003
co-sponsored by the Illinois Wheat Association & the Wheat Quality Council

written by J. Quinton


Wheat yield prospects across the southern half of Illinois and southwestern Indiana are potentially better than last yearís disappointing crop. The 2003 crop was seeded in very favorable conditions last fall and broke dormancy in very good condition this spring. Tiller populations are about 4% larger than last year. Thatís a nice positive. However, grain development is at risk. Frequent rains and heavy dews during the first half of May favored rapid development of wheat diseases. Septoria leaf and glume blotch has shown up this week on a considerable portion of the acres scouted. Bleached florets and the telltale pinkish residue of Head Scab (fusarium) were just becoming apparent as we counted tillers on this yearís Tour. This outbreak may not have run its course yet so we canít say what degree of yield loss and quality degradation may finally result. While the proportion of heads that were obviously infected with Head Scab on May 22nd ranged from less than 1% to about 20%, itís somewhat likely that more heads are going to be showing these effects over the next several days. Just how many additional infected heads there will turn out to be is the key question.

If it werenít for the lingering Head Scab assessment we could say that head size this year was generally much improved. During April and May of 2002 this area received widespread excessive rains, leaching fertilizers out of the root zone and causing extensive water damage to developing wheat. We recognized that we had to reduce the ratio of tillers-to-bushels in last yearís assessment to about 80% or so. Taking the 60 tillers per square foot observation from the 2002 Tour and applying that reduced ratio gave us a yield equivalent of only about 48 bushels per acre for the sampled counties. If it turns out that the fusarium outbreak this year is somewhat limited Ė much cooler temperatures arrived before heading was fully complete Ė we could say that a ratio closer to 1:1 will apply to this yearís average tiller count. Weíre crossing our fingers and hoping for that outturn, but follow up visits to scouted fields will tell us which way to go.

It was very apparent that wheat acreage is increased in Illinois and southwestern Indiana this year. Improved varieties, better wheat management know-how, and improving prices encouraged producers to put winter wheat back into their crop rotations last fall and to expand acreage where the wheat enterprise had never been taken out of the rotation. Itís a little soon to be certain, but it appears some of the newer varieties now being grown in the area have greater tolerance for the conditions that bring on Head Scab. Resistance to other diseases also has been successfully bred into the more recent soft red wheat lines and even better varieties are ready to be introduced.

The tendency is for people to want to compare this Tourís results with official statistics for the entire state, but that would be a fallacy. The data collected in this Tour are not exclusively from Illinois. We always include southwestern Indiana counties because of the similarity in climate and soil types. Even if we separated out the Illinois county data, the Tour information would not represent all Illinois wheat, but only about 75% to 80% of it. The value of this data set is mainly relational. Year-to-year differences should be the emphasized when citing the Tour results rather than comparison to official crop estimates. The percentage changes in tiller population are more useful than the absolute number of tillers. The apparent ratio of tiller densities to yield should also be highlighted rather than the yield per acre. In these ways the Annual Illinois Wheat Tour results are supplementary to the fuller, more carefully estimated official yield and production figures.


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7-yr avg tiller counts



Ohio & Miss Valley         (ILL/SW Ind)
























Remember:    With greater than normal head size we ought to boost the ratio above the 1:1 rule of thumb.  Two years ago the Tour determined that an enriched ratio would be appropriate.  With obvious stress we would want to reduce the ratio.


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