2017 ASHS Annual Conference

Artilleryweed is an annual or short-lived perennial weed that is becoming increasingly problematic in Florida, Hawaii, and other tropical and subtropical environments. Limited information is available on efficacy of commonly used herbicides on artilleryweed. The objective these experiments were to evaluate preemergence (PRE) and postemergence (POST) herbicides labeled for use in nurseries and/or landscapes for control of artilleryweed. All studies were conducted in Apopka, FL in a shaded greenhouse using standard soilless potting mix (pinebark + peat) and fertilizer amendments. Herbicides evaluated for POST control included diquat, dimethenamid-P, flumioxazin, glufosinate, glyphosate, indaziflam, oxadiazon, pelargonic acid, sulfentrazone and sulfosulfuron applied at 1× their highest label rate to mature (10 to 12 cm in height) artilleryweed. Data collection included bi-weekly visual control ratings for 8 weeks. At 8 weeks after treatment (WAT), shoot weights were determined. As this species often resumes growth soon after herbicide treatment, regrowth was assessed at four weeks after initial fresh weight collection. To evaluate preemergence herbicide efficacy, nursery pots filled with standard substrates and amendments and overseeded with artilleryweed seed and treated with either dimethenamid-P, indaziflam, isoxaben, oxadiazon, oxyfluorfen + prodiamine, oxyfluorfen + pendimethalin, pendimethalin, pendimethalin + dimethenamid-P, prodiamine, prodiamine + isoxaben, or S-metolachlor, or trifluralin + isoxaben. Weed counts, and percent weed coverage ratings were taken bi-weekly for 10 weeks. At 10 WAT, shoot fresh weights were recorded. Results showed that flumioxazin and glufosinate provided effective POST control although regrowth did occur following application with glufosinate. All herbicides evaluated provided over 90% control of artilleryweed when applied PRE with the exception of isoxaben and trifluralin + isoxaben. Results indicate that several effective options exist for artilleryweed management but more effective control will likely be achieved when herbicides are applied PRE. Due to prolific seed production, the addition of a PRE herbicide in a tank-mix with a suitable POST herbicide would be advised in areas that are heavily infested with artilleryweed.