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Providing evidence to improve practice

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

Key messages

Supporting evidence from individual studies

1 

A small, replicated, controlled, laboratory study conducted between 1999 and 2000 in New Zealand (Hofstra et al. 2006) found that the herbicide endothall reduced the growth of parrot’s feather Myriophyllum aquaticum. After 17 weeks, plants treated with endothall had a lower dry weight (29–57 g) than that of untreated plants (274 g). Plants were grown for approximately two months prior to herbicide application in 60 l plastic tubs. Endothall was sprayed onto plants in three tubs at a concentration of 9 and 15 kg/ha and plants in four tubs were left untreated.

2 

A replicated, controlled field study conducted between 2001 and 2002 in a wetland in the Northern Island of New Zealand (Hofstra et al. 2006) reported that treatment with the herbicide endothall reduced vegetation cover of parrot’s feather Myriophyllum aquaticum plants soon after application, but after 28 weeks cover was similar to pre-treatment levels. Results were not subject to statistical tests. After 10 weeks and following a second herbicide application, vegetation cover of treated plants was lower (2%) than untreated plants (47%). However, after 28 weeks, vegetation cover of treated plants (93%) was similar to that of untreated plants (97%). Authors reported that the increase in vegetation cover resulted from the encroachment of plants from outside sprayed areas rather than due to regrowth in treated plots. Endothall was applied at concentrations of 8.8 and 14.8 kg/ha. Each herbicide concentration was sprayed into three 5 x 5 m plots and three plots were left untreated. Herbicides were applied in early summer (December). A second application took place 51 days after the initial treatment.

3 

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.

Referenced papers

Please cite as:

Aldridge, D., Ockendon, N., Rocha, R., Smith, R.K. & Sutherland, W.J. (2018) Some aspects of control of freshwater invasive species. Pages 525-558 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2018. Open Book Publishers, Cambridge, UK.