Evaluation of a late summer imazapyr treatment for managing giant reed (Arundo donax).

Giant reed has invaded riparian habitats throughout California and the United States. Imazapyr, which can be used for California habitats with an appropriate application regime, has only been recently approved for use in controlling this species in California; therefore, little published data exists on its efficacy. We monitored a site where imazapyr had been applied with the purpose of testing the hypothesis that a 1.5% solution of imazapyr applied as a foliar spray was effective at killing giant reed. Plants treated with 1.5% imazapyr had reduced leaf chlorophyll content less than 30 days after treatment but recovered the following spring. Treatment with 1.5% imazapyr did not significantly reduce the proportion of living stems or prevent the production of new stems during the spring following treatment. 1