After making a bunch of extension presentations, and following our 2012 publication of “Preemergent control of medusahead on California annual rangelands with aminopyralid” (Rangeland Ecology & Management 65:418-425), I’ve talked with quite a few ranchers who have successfully used Milestone® preemergence at 7 to 14 oz/acre to control medusahead. (See this blog post.) I should note here that 7 oz of Milestone is the maximum broadcast rate; 14 oz is labelled only for spot treatments.
Recently, Matt Rinella (USDA-ARS, Montana) found that aminopyralid controls seed set in medusahead in the greenhouse. He previously demonstrated this effect for Japanese brome in field tests. So in cooperation with Matt, Jeremy James (UCCE Sierra Foothill Research & Extension Center), and Josh Davy (UCCE Farm Advisor, Tehama, Glenn, and Colusa counties), Joe DiTomaso and I are running field tests using spring applications of aminopyralid on medusahead. The advantages to this timing – if the applications successfully prevent seed production – will be (1) it might be possible to use lower rates (we’re trying 3, 7, and 14 oz/acre of Milestone); (2) treatments can be applied after most forage grasses have seeded out, so even if they were susceptible they won’t be affected; and (3) no effect on summer forage.
We will collect seedheads and test for viability, and follow the sites over two years to compare long-term effects of the spring treatments with fall treatments at 7 and 14 oz. Sure hope it works!
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