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Providing evidence to improve practice

Action: Parrot’s feather: Use of herbicides - diquat Control of Freshwater Invasive Species

Key messages

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Supporting evidence from individual studies

1 

A replicated, randomized, controlled, field study conducted in summer 1986 in Portugal (Moreira et al. 1999) found that the application of the herbicide diquat did not reduce the biomass of parrot’s feather Myriophyllum aquaticum. For three out of three comparisons, the fresh weight of parrot’s feather plants treated with diquat did not differ from untreated plants (15–25 vs 22–26 kg/m2). Additionally, the biomass of parrot’s feather plants treated with diquat (15–25 kg/m2) was higher than that of plants treated with 2,4-D amine (2–9 kg/m2) for three out of three comparisons, was higher than that of plants treated with gluphosinate-ammonium (9–22 kg/m2) for five out of nine comparisons, and was higher than of plants treated with glyphosate (9–14 kg/m2) for two out of three comparisons. Parrot’s feather biomass was assessed in 20 x 7 m plots and each herbicide rate was tested in four replicates. Herbicide rates were 2 kg/ha for diquat, 6.5 kg/ha for 2,4-D amine, 1–2.4 kg/ha for gluphosinate-ammonium and 3.6 kg/ha for glyphosate.

2 

A small, replicated, randomized, controlled, laboratory study conducted in 2006 in the USA (Wersal et al. 2010), found that the application of the herbicide diquat reduced growth of parrot’s feather Myriophyllum aquaticum. After four weeks, the dry weight of parrot’s feather plants treated with diquat was lower than untreated plants (1–3 vs 6 g/pot). Daytime and night-time application of the herbicide resulted in similar results. Parrot’s feather shoots were propagated in 3.78 l pots and placed inside 246 l containers filled with water. Each herbicide rate (0.19 and 0.37 mg/l) was applied to three plants.

3 

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.

Referenced papers

Please cite as:

Aldridge, D., Ockendon, N., Rocha, R., Smith, R.K. & Sutherland, W.J. (2019) Some aspects of control of freshwater invasive species. Pages 569-602 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.