Four field studies were initiated between January and February of 2022 in commercial Christmas tree farms in the Willamette Valley. The trees were Douglas fir and Nordman fir in the second year after transplanting. A single application was made over the top of the young trees mimicking growers’ practices with other herbicides.
The study is ongoing, but I will share some data from 12 weeks after the treatment. To date, no crop injury has been observed in any of the studies in Douglas Fir or Nordman fir treated with Fluridone at the expected field rate and twice that, equivalent to a Brake On! rates 43 and 83 fl oz/A. These encouraging results include growth measurements unaffected to date by these treatments. Growth measurement data are not shown.
Most of the research sites had low weed pressure, making it difficult to assess weed control. Postemergence herbicides were not included in the treatments. One of the fields planted with Nordman firs was infested with false dandelion (Hypochaeris radicata) and rattail fescue (Vulpia myuros). Most of the treatments did not provide good control of false dandelion that was present at the time of the application. Fluridone did not control false dandelion (<28%) regardless of the rate but did control rattail fescue (58 – 85%) (Table 1). When Brake on was used in mixtures, the mixture of simazine + Goal Tender + Brake On resulted in 73% control of false dandelion and 91% control of rattail fescue. Cleantraxx controlled 86% of false dandelion and 92% of rattail fescue.