Happy New Year! It’s too cold in Tulelake for field work, so I’m busy summarizing 2013 research results. Today I posted a progress report on the Intermountain Research and Extension Center (IREC) website summarizing results for our 2013 onion weed control research. The study was conducted at IREC to evaluate rates of DCPA (Dacthal) alone and combined with pendamethalin (Prowl H20) applied at loop stage for control of kochia in onions grown on silty clay soil with high organic matter. Sulfentrazone (Zeus), an unregistered herbicide in onions, was tested at various rates as a preemergence and postemergence herbicide on the same soil type. Prowl H20 application timing was also evaluated by comparing applications immediately after planting and at the loop stage.
Results showed that Dacthal in combination with Prowl H20 at loop stage worked significantly better than Dacthal or Prowl H20 alone for controlling kochia. Kochia control was superior when Prowl H20 was applied immediately after planting compared to Prowl H20 applied at loop stage. Zeus (unregistered herbicide) applied at the 3 fl oz/A rate immediately after planting or at the 3-leaf stage was safe on onions and provided over 88% control of kochia. Zeus applied at 4 fl oz/A immediately after planting and at 2 fl oz/A at the loop stage caused unacceptable onion stand loss and yield reduction, so the rate and application timing of Zeus appears to be a very important in achieving crop safety. For more information and a complete summary of results check out the progress report on the IREC website: http://ucanr.edu/sites/Intermountain_REC/files/179349.pdf