Return on investment by spraying tebuconazole for leaf rust in 2009, 2010, and 2011 on these four varieties was marginal at best (Tables 2, 3, and 4). Leaf rust pressure on all of these varieties was very low. The positive returns we observed on Terral LA 841 and Pioneer 25R47 in 2009 were achieved by controlling glume blotch, not leaf rust.

Leaf rust pressure was also very low in 2012. However, we did experience a damaging glume blotch infection across the region, and spraying tebuconazole provided a very good return on investment at the Howe location (Table 5).

Over the period from 2009 through 2011, tebuconazole did not provide a positive return on investment in 13 out of 28 observations, even though the breakeven cost of this application was just a little over a bushel per acre. With a few exceptions, this was a measure of the value of controlling leaf rust in Terral LA 841, Magnolia, Pioneer 25R47, and Coker 9553. Control of glume blotch was the reason we saw a positive return on investment with tebuconazole with these varieties in 2009 in Royse City and 2012 in Howe.

These data demonstrate that a grower cannot afford to spend very much money on a foliar fungicide to spray commercial varieties with some level of rust resistance. If we had used a $16.00 fungicide instead

of tebuconazole from 2009-2011, the breakeven would have been 3.5 bushels per acre, and the fungicide would have only been profitable 5 out of 28 times (Table 6). Rust pressure is usually too low on these varieties to damage them, and a fungicide will not consistently provide a positive return on investment. The decision to use a fungicide on varieties resistant or moderately resistant to leaf rust should be based primarily on the threat of glume blotch.

CONCLUSIONS

The formula for success in growing wheat in Northeast Texas is quite simple. Plant several high yielding resistant varieties in a timely manner, manage for optimum yet realistic yields, and use an inexpensive foliar fungicide to protect yourself against a leaf rust race change or late season glume blotch infection.

 

 J. Swart, Entomologist (IPM), Texas A&M AgriLife Extension; A. Braley, Research Technician, Texas A&M University-Commerce; R. Sutton, Assistant Research Scientist, Texas A&M AgriLife Research; Scott Stewart, Research Technician, Texas A&M University-Commerce, Donald Reid, Agronomy Professor (retired), Texas A&M University-Commerce

 

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