Brazilian peppertree and mangrove species response to foliar-applied novel auxin-type herbicides

Abstract

AbstractBrazilian peppertree (Schinus terebinthifoliaRaddi) is an invasive shrub that is problematic in both freshwater wetlands and brackish mangrove communities. The complex structure, geographic remoteness, and general herbicide sensitivity of mangrove systems have resulted in great technical challenges for managers attempting selectiveS. terebinthifoliacontrol. Recent advances in auxin herbicide technologies warrant herbicide screening to address this growing problem. Therefore, greenhouse experiments were conducted in 2018 and 2019 to evaluate four non-target mangrove species andS. terebinthifoliaresponse to the three herbicides: aminocyclopyrachlor, aminopyralid, and florpyrauxifen-benyzl. Aminocyclopyrachlor controlledS. terebinthifolia, but was highly injurious to black mangrove [Avicennia germinans(L.) L.], red mangrove (Rhizophora mangleL.), white mangrove [Laguncularia racemosa(L.) C.F. Gaertn.], and buttonwood mangrove (Conocarpus erectusL.). Aminopyralid also controlledS. terebinthifoliabut its impact varied across mangrove species.Laguncularia racemosaandC. erectuswere highly sensitive to aminopyralid,R. mangleexhibited dose-dependent tolerance, andA. germinanswas highly tolerant. Florpyrauxifen-benzyl failed to controlS. terebinthifoliaand resulted in severe injury to all four mangrove species. These results indicate differential responses to newer auxins in both the target response and non-target plant community of interest. The efficacy of aminopyralid onS. terebinthifolia, coupled with its selectivity onA. germinanswarrants further testing.