Pretassel Applications Of Strobilurin Fungicides Can Cause ‘Beer Can’ Ears

DR. DON HERSHMAN LEXINGTON, KY.

PRINCETON, KY.

Corn ears with the markedly reduced ear size shown in Figure 1 go by several names: “beer can” ears, blunt ear syndrome, ear stunting, and arrested ear syndrome. The length of the husk and number of kernel rows are often normal, but the number of kernels per row is often greatly reduced.

   Cold shock while corn is in the V8-V12 stage is thought to be one possible cause, but the pretassel application of certain strobilurin fungicides can also cause such symptoms. Literature from BASF, the manufacturer of Headline ®, indicates that this has been seen only 0.25 percent of treated fields. This literature also indicates that the problem has only been associated with applications which included an adjuvant such as a nonionic surfactant.

   BASF’s recommendation for Headline® is as follows:

   1. Pre-tassel application. Product may be applied by ground rig but without an adjuvant. If applying by aerial application, apply in at least 5 gal/acre and without an adjuvant. Do not apply Headline® in less than 5 gal/acre.

   2. VT through R2 application. Product may be applied aerially in at least 5 gal/acre or by ground rig; the use of an adjuvant is flexible. If applying aerially in less than 5 gal/acre, include crop oil in spray.

   Although this specific syndrome has only been associated with fungicide application in less than 1 percent of treated fields, it is important to note that yield loss was frequently associated with application of strobilurin fungicides in tests conducted in 2007 by university researchers (Figure 2). We don’t fully understand all the reasons these yield losses occur. Some of these may be explained by natural variation (random chance), but then again, natural variation may also explain some of the yield increases that occur. In any case, the possibility of yield loss is something to be aware of when considering the use of strobilurin fungicides on corn. Δ

    Dr. Paul Vincelli is Extension Plant Pathologist with the University of Kentucky at Lexington and Dr. Don Hershman is Extension Plant Pathologist with the University of Kentucky at Princeton.