Comparison of subsurface and foliar herbicide applications for control of parrotfeather (Myriophyllum aquaticum)

Parrot’s feather: Use of herbicides - diquat

A small, replicated, controlled, laboratory study conducted between 2007 and 2008 in the USA (Wersal & Madsen 2010), found that the application of the herbicide diquat reduced growth in parrot’s feather Myriophyllum aquaticum. After six weeks, the dry weight of parrot’s feather plants treated with diquat was reduced compared to untreated plants (2–6 vs 18 g/pot). Six weeks after application, diquat had controlled parrot’s feather plants by 50–70% (visual assessment, with 0% corresponding to no control and 100% to complete control). Parrot’s feather shoots were propagated in 3.78 l pots and placed inside 246 l containers filled with water. Each herbicide rate (subsurface: 0.19 and 0.37 mg/l; foliar: 4.5 kg/ha) was applied to four 246 l containers, each holding four plants. Number of plants used as control is not presented and control in the context of the visual assessments was not clearly defined.

Parrot’s feather: Use of herbicides - endohall

A small, replicated, controlled, laboratory study conducted between 2007 and 2008 in the USA (Wersal & Madsen et al. 2010), found that the application of the herbicide endothall above a certain concentration reduced the growth of parrot’s feather Myriophyllum aquaticum. After six weeks, the dry weight of parrot’s feather plants treated with endothall at a concentration of 5 mg/l was lower than that of untreated plants (12 vs 18 g/pot) but the dry weight of plants treated with endothall at a concentration of 2.5 mg/l did not differ from untreated plants (17 vs 18 g/pot). Visual assessment revealed no reduction in vegetation by endothall at either concentration six weeks after herbicide application (0% change relative to untreated plants). Parrot’s feather shoots were propagated in 3.78 l pots and placed inside 246 l containers filled with water. Each herbicide rate was applied to four 246 l containers, each holding four plants. Number of plants used as control is not presented. Visual assessments were expressed in percentage, with 0% corresponding to no control and 100% to complete control.

(Summarised by: Ricardo Rocha)

Parrot’s feather: Use of herbicides - triclopyr

A small, replicated, controlled, laboratory study conducted between 2007 and 2008 in the USA (Wersal & Madsen, 2010), found that the application of the herbicide triclopyr reduced growth in parrot’s feather Myriophyllum aquaticum. After six weeks, the dry weight of parrot’s feather plants treated with triclopyr was lower than that of untreated plants (3–6 vs 10 g/pot). Subsurface and foliar herbicide applications led to similar changes in biomass. Six weeks after application, triclopyr had controlled parrot’s feather by 15–70% (visual assessment with 0% corresponding to no control and 100% to complete control). Parrot’s feather shoots were propagated in 3.78 l pots and placed inside 246 l containers filled with water. Each herbicide rate (subsurface: 1.25 and 2.5 mg/l; foliar: 6.7 kg/ha) was applied to four 246 l containers, each holding four plants. Number of plants used as control is not presented and control in the context of the visual assessments was not clearly defined.

(Summarised by: Ricardo Rocha)

Parrot’s feather: Use of herbicides - carfentrazone-ethyl

A small, replicated, controlled, laboratory study conducted between 2007 and 2008 in the USA (Wersal & Madsen 2010) found that the application of the herbicide carfentrazone-ethyl reduced growth of parrot’s feather Myriophyllum aquaticum. After six weeks, the dry weight of parrot’s feather plants treated with carfentrazone-ethyl was lower (10–12 g/pot) than that of untreated plants (18 g/pot). Six weeks after application, plants treated with carfentrazone-ethyl were reduced by 0–15% (visual assessment with 0% corresponding to no reduction in cover relative to untreated plans and 100% to complete elimination). Parrot’s feather shoots were propagated in 3.78 l pots and placed inside 246 l containers filled with water. Each herbicide rate (0.1 and 0.2 mg/l) was applied to four 246 l containers, each holding four plants. Number of plants used as control is not presented.

(Summarised by: Ricardo Rocha)

Parrot’s feather: Use of herbicides - 2,4-D

A small, replicated, controlled, laboratory study conducted between 2007 and 2008 in the USA (Wersal et al. 2010), found that the application of the herbicide 2,4-D above a certain concentration reduced growth in parrot’s feather Myriophyllum aquaticum. After six weeks, the dry weight of plants treated with subsurface 2,4-D at a concentration of 5 mg/l was lower than that of untreated plants (10 vs 18 g/pot). However, the dry weight of plants treated with 2,4-D at a concentration of 2 mg/l did not differ from that of untreated plants (15 vs 18 g/pot). Dry weight of plants exposed to foliar application of 2,4-D (1 g/pot) was lower than untreated plants or those treated with 2,4-D underwater. Parrot’s feather shoots were propagated in 3.78 l pots and placed inside 246 l containers filled with water. Each herbicide rate was applied to four 246 l containers, each holding four plants. Number of plants used as control is not presented.

Parrot’s feather: Use of herbicides - other herbicides

A small, replicated, controlled, laboratory study conducted between 2007 and 2008 in the USA (Wersal & Madsen, 2010) found that the application of the herbicide copper chelate did not affect the growth of parrot’s feather Myriophyllum aquaticum. After six weeks, the dry weight of parrot’s feather treated with copper chelate (14–16 g/pot) did not differ significantly from the biomass of untreated plants (18 g/pot). Visual assessment revealed no reduction in plant vegetation by copper chelate compared to untreated controls six weeks after herbicide application. Parrot’s feather shoots were propagated in 3.78 l pots and placed inside 246 l containers filled with water. Each herbicide rate (0.5 and 1 mg/l) was applied to four 246 l containers, each holding four plants. Number of plants used as control is not presented and control in the context of the visual assessments was not clearly defined.

(Summarised by: Ricardo Rocha)