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Fusarium Head Blight, Fungicides and Rye?

Rye too is susceptible to Fusarium head blight or scab. Likewise the presence of deoxynivalenol or vomitoxin will result in steep discounts in rye too.  Interestingly enough the presence of vomitoxin does not influence the suitability to mash it and distill it for whiskey.  Unfortunately very little research has been done to date to look at the efficacy of fungicides in rye.

Rye reaches heading and the grain fill period even a bit sooner than winter wheat; the first hybrid rye fields in southern Minnesota are heading as I write this. Like winter wheat, rye will escape the scourge of FHB most years in Minnesota, simply by being this early. And while escape is a perfectly good approach it is not a failsafe method is a climate as variable as Minnesota’s.

The question of whether a fungicide can help reduce the incidence and severity of FHB rye therefor warrants some attention.  Unlike the other small grains rye is a cross-pollinating species.  If an application of a fungicide to reduce scab at Feekes 10.5 (fully headed) or Feekes 10.51 (beginning of pollen shed) interferes with the pollen shed and/or seed set than any benefits to reduce scab might be offset by reducing grain yields or even an increase in the incidence of ergot as ergot thrives when fertilization and seed set are hampered resulting in the florets remaining open longer than necessary.

Drs. Chad Lee and Carl Bradley at the University of Kentucky have started to evaluate the efficacy of Caramba and Miravis Ace fungicides applied at Feekes 10.5, Feekes 10.51, and 5 days after the beginning of pollen shed on hybrid rye.  Their preliminary findings and conclusions are that rye benefits from fungicides much the same way wheat does while they did not observe any adverse effects in pollination or seed set in each of the 2 years the trial is now underway.  Like with wheat, grain yield and test weight improved significantly while the incidence and severity of scab were reduced significantly.  The yield increases and reductions observed are similar to those observed in trials with wheat, with an up to 80% overall reduction in scab compared to the untreated control. 

They did not report an increase in the incidence of ergot. This in combination with the increase in grain yield suggests that the application at any of the three timings did not interfere with pollen shed or seed set. 

In short, it appears that an application of Caramba or Miravis Ace (Prosaro or formulations of tebuconazole were not tested) can reduce the incidence and severity of scab in rye.  Approach it the same way you would for winter wheat; keep an eye out for the weather, consult the risk models to determine the risk of scab in your area, and apply the fungicide at Feekes 10.51 if you can, or up to 5 days after Feekes 10.51 if you are forced to.

PS) The disease forecasting systems and the weekly commentaries about diseases and pests in small grains will resume after this Memorial Day weekend.

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