Collected Evidence: Collected Evidence: Procambarus crayfish control: Encouraging predators Two replicated, controlled studies in Italy found that eels fed on the red swamp crayfish and reduced population size. One replicated, controlled study from France in 2001 found that pike predated red swamp crayfish.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1030https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1030Fri, 03 Jul 2015 15:15:43 +0100Collected Evidence: Collected Evidence: Procambarus crayfish control: Trapping combined with encouragement of predators A before-and-after study in Switzerland found that introducing predators, combined with trapping significantly reduced red swamp crayfish populations in a pond. A second replicated, controlled study from Italy demonstrated that trapping and predation in combination was more effective at reducing red swamp crayfish populations than predation alone.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1031https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1031Fri, 03 Jul 2015 15:16:05 +0100Collected Evidence: Collected Evidence: American bullfrog control: Direct removal of adults One replicated study in Belgium found catchability of adult bullfrogs in small shallow ponds using one double fyke net for 24 h to be very low. One small study in the USA found that bullfrog adults can be captured overnight in a single trap floating on the water surface. One replicated, controlled study in the USA found that bullfrog populations rapidly rebounded following intensive removal of the adults. One before-and-after study in France found a significant reduction in the number of recorded adults and juveniles following the shooting of metamorphosed individuals before reproduction, when carried out as part of a combination treatment.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1045https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1045Fri, 03 Jul 2015 15:20:46 +0100Collected Evidence: Collected Evidence: American bullfrog control: Direct removal of juveniles One replicated study in Belgium found double fyke nets were effective in catching bullfrog tadpoles in small shallow ponds. One before-and-after study in France found a significant reduction in the number of recorded adults and juveniles following the removal of juveniles by trapping, when carried out as part of a combination treatment.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1046https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1046Fri, 03 Jul 2015 15:20:59 +0100Collected Evidence: Collected Evidence: Brown and black bullheads: Application of a biocide A study in the UK reported that use of a piscicide containing rotenone achieved eradication of black bullhead. A study in the USA found that rotenone successfully eradicated black bullhead, but one of two ponds required two separate doses.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1050https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1050Wed, 07 Oct 2015 10:41:27 +0100Collected Evidence: Collected Evidence: Red-eared terrapin: Direct removal of adults A replicated field study in Spain found that Aranzadi turtle traps were effective in trapping red-eared terrapins from a river but did not eradicate the population. A study in the British Virgin Islands found that using sein nets to trap adults and juveniles was not successful in eradicating the population.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1055https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1055Tue, 13 Oct 2015 11:56:26 +0100Collected Evidence: Collected Evidence: Ponto-Caspian gammarids: Control movement of gammarids A replicated, controlled laboratory study in the USA found that movements of invasive freshwater shrimp slowed down or stopped when they were placed in water that had been exposed to different species of predatory fish, compared to those not exposed to fish. A replicated laboratory study in the UK found carbonating the water stunned invasive killer shrimp.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1088https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1088Tue, 13 Oct 2015 13:28:18 +0100Collected Evidence: Collected Evidence: Ponto-Caspian gammarids: Change salinity of the waterOne of two replicated laboratory studies (one controlled) in Canada and the UK found that increasing the salinity level of water killed the majority of invasive shrimp within five hours. One found that increased salinity did not kill invasive killer shrimp.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1091https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1091Tue, 13 Oct 2015 13:36:28 +0100Collected Evidence: Collected Evidence: Skunk cabbage: Physical removal A study in Switzerland found that annual physical removal of recently established skunk cabbage plants over five years removed the entire stock. A study in the Netherlands found that manual removal of mature skunk cabbage plants was effective for a small outbreak of a small-growing plant. A study in Germany reported that after the first four years of a twice yearly full removal programme of skunk cabbage, a large number of plants still needed to be removed each year. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1101https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1101Tue, 13 Oct 2015 14:11:52 +0100Collected Evidence: Collected Evidence: Skunk cabbage: Chemical control using herbicides A study in the UK found that two herbicides, glyphosate and 2, 4-D Amine, both killed all skunk cabbage plants in test areas. However, another study in the UK found that although using 2,4-D amine at 9 litres/ha, successfully eradicated skunk cabbage, using glyphosate was unsuccessful at eradicating skunk cabbage, with only limited reduction in growth of the plants. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1102https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1102Tue, 13 Oct 2015 14:18:08 +0100Collected Evidence: Collected Evidence: Asian clams: Add chemicals to the water A replicated laboratory study in the USA found that dosing with the biocides chlorine, potassium and copper killed Asian clams. A controlled, replicated laboratory study and a controlled, replicated field study in the USA found that higher concentrations of chlorine and bromine, delivered at higher temperatures, shortened the time required to kill the Asian clams. A controlled field-based trial in Spanish irrigation systems showed that fat-coated particles called BioBullets could kill 100% of the Asian clams within pipes. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1118https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1118Tue, 13 Oct 2015 14:59:51 +0100Collected Evidence: Collected Evidence: Water primrose: Chemical control using herbicides A controlled, replicated laboratory study in the USA found that the herbicide triclopyr TEA applied at concentrations of 0.25% killed 100% of young cultivated water primrose within two months. A before-and-after field study in the UK found that the herbicide glyphosate controlled water primrose, causing 97% mortality when mixed with a non-oil based sticking agent and 100% mortality when combined with TopFilm. A controlled, replicated, randomized study in Venezuela3, found that use of the herbicide halosulfuron-methyl (Sempra) resulted in a significant reduction in water primrose coverage without apparent toxicity to rice plants. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1139https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1139Tue, 13 Oct 2015 16:14:37 +0100Collected Evidence: Collected Evidence: Crassula helmsii: Chemical control using herbicides Seven studies (including one replicated and controlled study) in the UK, found that applying glyphosate reduced Crassula helmsii. In one before-and-after study at a single site glyphosate applied in combination with diquat reduced C. helmsii by 98%. Another before-and-after study at a single site found that covering C. helmsii with carpet before treating with glyphosate resulted in an 80% reduction in the plant. Three out of four studies (including one controlled study) in the UK found that applying diquat or diquat alginate reduced cover or eradicated submerged C. helmsii. One before-and-after study at a single site found that applying both diquat and glyphosate reduced C. helmsii by 98%. One small, before-and-after trial found no effect of diquat or diquat alginate on cover of C. helmsii. One out of two studies (including one replicated, controlled study) in the UK, found that treating submerged C. helmsii with dichlobenil in container trials led to partial reduction in its biomass. One small before-and-after field study found no effect of dichlobenil on C. helmsii. One replicated, controlled container trial in the UK found that treatment with terbutryne partially reduced biomass of submerged C. helmsii. The same study found reductions in emergent C. helmsii following treatment with asulam, 2,4-D amine and dalapon. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1279https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1279Tue, 05 Jul 2016 16:29:26 +0100Collected Evidence: Collected Evidence: Crassula helmsii: Use hot foam to control plants One replicated, controlled study in the UK found that treatment with hot foam, along with other treatments, did not reduce cover of Crassula helmsii. One before-and-after study in the UK found that applying hot foam partially destroyed C. helmsii.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1286https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1286Tue, 12 Jul 2016 08:56:05 +0100Collected Evidence: Collected Evidence: Crassula helmsii: Use salt water to kill plants Two replicated, controlled container trials and two before-and-after field trials in the UK found that seawater eradicated Crassula helmsii.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1288https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1288Tue, 12 Jul 2016 09:14:42 +0100Collected Evidence: Collected Evidence: Crassula helmsii: Use lightproof barriers to control plants Five before-and-after studies in the UK found that covering Crassula helmsii with black sheeting or carpet strips eradicated or severely reduced the cover of the plant. However, C. helmsii was reported to have progressively recolonized two of the sites where it had been had initially been reported as eradicated.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1294https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1294Tue, 12 Jul 2016 09:39:41 +0100Collected Evidence: Collected Evidence: Crassula helmsii: Use grazing to control plants One of two replicated, controlled studies in the UK found that excluding grazing reduced the abundance and coverage of Crassula helmsii. The other study found no difference in cover of C. helmsii between ungrazed and grazed plots. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1301https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1301Tue, 12 Jul 2016 10:48:03 +0100Collected Evidence: Collected Evidence: Parrot’s feather: Biological control using herbivores One replicated, controlled laboratory study in Portugal found that grass carp did not reduce biomass or cover of parrot’s feather. Two replicated, randomized field studies in Argentina and the USA found that stocking with grass carp reduced the biomass or abundance of parrot’s feather. One field study in South Africa reported reduced growth of parrot’s feather following the release a South American leaf-feeding Lysathia. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1599https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1599Fri, 20 Oct 2017 14:58:11 +0100Collected Evidence: Collected Evidence: Parrot’s feather: Reduction of trade through legislation and codes of conduct One randomized, before-and-after trial in the Netherlands reported that the implementation of a code of conduct reduced the trade of aquatic plants banned from sale (group that included parrot’s feather Myriophyllum aquaticum). One study in the USA found that parrot’s feather plants were still traded despite a state-wise trade ban. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1604https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1604Fri, 20 Oct 2017 15:14:50 +0100Collected Evidence: Collected Evidence: Parrot’s feather: Use of herbicides - 2,4-D Three laboratory studies (including two replicated, controlled studies and one randomized, controlled study) in the USA and Brazil found that the herbicide 2,4-D reduced the growth of parrot’s feather. One replicated, controlled laboratory study in Brazil found that 2,4-D led to a greater reduction in growth of parrot’s feather than the herbicides diquat, glyphosate or imazapyr. One replicated, randomized, controlled field study in Portugal found that 2,4-D amine reduced the biomass of parrot’s feather. One randomized, controlled field study in Portugal found that the combined application of 2,4-D and MCPA completely eliminated parrot’s feather. One randomized, controlled laboratory study in the USA found that the combined application of 2,4-D and carfentrazone-ethyl led to a higher reduction in the cover of parrot’s feather than the application of the herbicide dichlobenil eight days after treatment but not 45 days after treatment. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1606https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1606Fri, 20 Oct 2017 16:31:34 +0100Collected Evidence: Collected Evidence: Parrot’s feather: Use of herbicides - carfentrazone-ethyl Five laboratory studies (including one replicated, controlled, before-and-after study) in the USA found that carfentrazone-ethyl reduced growth in parrot’s feather. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1676https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1676Mon, 23 Oct 2017 08:54:36 +0100Collected Evidence: Collected Evidence: Parrot’s feather: Use of herbicides - diquat Two laboratory studies (including a replicated, randomized, controlled study) in the USA found that diquat reduced the growth of parrot’s feather. One replicated, randomized, controlled field study in Portugal found that growth was not reduced after the application of diquat. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1680https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1680Mon, 23 Oct 2017 09:11:46 +0100Collected Evidence: Collected Evidence: Parrot’s feather: Use of herbicides - endohall Two replicated, controlled laboratory studies in New Zealand and the USA found that endothall reduced the growth of parrot’s feather. One replicated, randomized, controlled field study in New Zealand found that parrot’s feather plants treated with endohall presented lower cover soon after herbicide application but cover later increased to levels similar to pre-treatment. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1681https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1681Mon, 23 Oct 2017 09:16:19 +0100Collected Evidence: Collected Evidence: Parrot’s feather: Use of herbicides - triclopyr Two replicated, controlled laboratory studies in New Zealand and the USA reported reduced growth of parrot’s feather following treatment with triclopyr. One replicated, before-and-after and one replicated, controlled field study in New Zealand found that cover was reduced after treatment with triclopyr. However, one of the studies noted that cover later increased to levels close to pre-treatment. One replicated, controlled laboratory study in New Zealand found that the application of triclopyr led to a greater reduction in cover than the application of glyphosate. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1689https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1689Mon, 23 Oct 2017 10:03:03 +0100Collected Evidence: Collected Evidence: Parrot’s feather: Use of herbicides - other herbicides One replicated, controlled laboratory study in New Zealand found that the application of dichlobenil reduced the growth of parrot’s feather. Two replicated, randomized, controlled field studies in Portugal and New Zealand found that the application of dichlobenil reduced cover less than the combined application of the herbicides 2,4-D and MCPA eight days after treatment but not 45 days after treatment and that plants treated with dichlobenil presented lower vegetation cover soon after herbicide application but cover later increased to levels close to pre-treatment. Three laboratory studies (including two replicated, controlled studies and one randomized, controlled study) in the USA found that the herbicides imazamox and imazapyr reduced the growth of parrot’s feather. One replicated, randomized, controlled field study in Portugal and one replicated, controlled, laboratory study in the USA reported reduced parrot’s feather biomass after treatment with glyphosate. One replicated, randomized, controlled field study in Portugal found that the application of gluphosinate-ammonium reduced the biomass of parrot’s feather. Three replicated, controlled laboratory studies in New Zealand and the USA found that treatment with fluridone, clopyralid and copper chelate did not reduce growth of parrot’s feather. One replicated, controlled laboratory study in the USA found that the application of flumioxazin reduced the growth of parrot’s feather. One replicated, randomized, controlled laboratory study in the USA found that the application of florpyrauxifen-benzyl reduced the growth of parrot’s feather. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1699https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1699Mon, 23 Oct 2017 11:11:47 +0100
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 21

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.


Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust