Action: Floating pennywort: Chemical control using herbicides
Key messagesRead our guidance on Key messages before continuing
- A controlled, replicated study in the UK found that the herbicide 2,4-D amine applied at 4.2 kg/ha achieved near to 100% mortality, compared with the herbicide glyphosate applied at 2.2 kg active ingredient/ha (without an adjuvant) which achieved negligible mortality.
Application of chemical herbicides may offer a localised tool for management of floating pennywort Hydrocotyle ranunculoides provided regulatory approvals are in place. It is possible that efficacy will be enhanced by use of agents called adjuvants to bond the herbicide to the leaf surface, and the most effective adjuvants may show seasonality. For example, an information sheet published in the UK suggests that applications of 4-6 L/ha in 200 L water with an adjuvant called TopFilm at 1.2 L/ha work up to the middle of July whereas applications of 4–6 L/ha with a Codacide Oil adjuvant work from July onwards (Newman & Duenas 2010).
Newman J.R. & Duenas M.A. (2010) Information sheet: control of floating pennywort (Hydrocotyle ranunculoides). Centre for Ecology & Hydrology, Wallingford, UK. 3pp.
Supporting evidence from individual studies
A controlled, replicated field experiment in 1997 in the Addlestone Bourne flood relief channel England, UK (Newman & Dawson 1999) found that the herbicide 2,4-D amine achieved near to 100% mortality, compared with the herbicide glyphosate which achieved negligible mortality. The chemical 2,4-D amine applied at 4.2 kg/ha achieved 76% decrease in floating pennywort Hydrocotyle ranunculoides biomass and almost 100% mortality over the first four weeks of treatment. In comparison, treatment with glyphosate applied at 2.2 kg/ha (without an adjuvant) resulted in a 20% decrease in biomass over the first four weeks and negligible mortality. Two trial plots in a 65m section of the channel were marked out and subdivided into six treatment blocks. Two blocks were sprayed in 2,4-D amine, two in glyphosate, and two were left untreated in control plots. Wet weight of root and shoot material/m2 was taken before treatment, and each week after treatment for four weeks following herbicide application. Percentage cover measurements were made each week until nine weeks after spraying.