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Observe preharvest intervals for small-grain fungicides

Agriculture.com Staff 07/03/2008 @ 9:25am

The recent temporary embargo on 40 Kansas wheat fields is still a reminder to observe fungicide preharvest intervals (PHI).

In question were late applications of Quilt and Bumper, fungicides that require a waiting period between application and harvest. Quilt requires 45 days and Bumper 40 days. Their active ingredients have a low toxicity in humans. However, residue on grain must not exceed limits established by the U.S. Environmental Protection Agency and the U.S. Food and Drug Administration.

Some of the wheat samples pulled from these fields showed no detectible traces of Quilt fungicide residue at all, while others showed levels below the tolerance established the U.S. Environmental Protection Agency and the U.S. Food and Drug Administration. Fields treated with Bumper, a fungicide similar to Quilt, also tested below federal tolerances.

"Now that the integrity of Kansas wheat is assured, we can focus on gathering facts that will tell us whether the products were applied at the proper stage of plant growth," Polansky says.

Because the crop matured later than usual due cool, damp weather, Polansky says it's possible the timing of the applications was appropriate for the plant's development but ill-advised, given the PHIs for the fungicides.

The KDA currently is not placing any restrictions on harvest. However, they remind producers that failing to abide by a PHI violates state and federal law and opens the producer to enforcement action.

Marcia McMullen, North Dakota State University (NDSU) Extension plant pathologist, notes in North Dakota, the following PHIs apply for registered small grain fungicides:

Product / PHI

  • Headline* / Feekes 10.5 (approximately 40 days PHI)
  • Quadris / 45 days
  • Caramba / 30 days
  • Folicur** / 30 days
  • Proline / 30 days wheat, 32 days barley
  • Tilt** / 40 days
  • Quilt / 45 days
  • Stratego / 35 days

* Headline is the only product that doesn't specify number of days in their PHI. Feekes (a wheat growth scale) 10.5 is approximately 40 days before harvest in North Dakota, depending on air temperatures. Hot temperatures push the crop to flowering, Feekes 10.51, more quickly.

** Additional tebuconazoles such as Orius, etc., or additional propiconazoles, such as Propimax, etc., have North Dakota state supplemental labels that specify the same PHIs as the original registered products.

Products recommended by NDSU for heading or flowering application for Fusarium head blight suppression all have 30 day PHIs in wheat (32 days for Proline in barley), a duration that should allow ample time in ND for maturity before swathing or harvest.

"Producers and applicators need to take heed of these PHIs, as what happened in Kansas is a very strong reminder that labels are the law and must be followed," she says.

The recent temporary embargo on 40 Kansas wheat fields is still a reminder to observe fungicide preharvest intervals (PHI).

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