Action: Introduce an organism to control problematic plants
Key messagesRead our guidance on Key messages before continuing
- One study evaluated the effects, on peatland vegetation, of introducing an organism (other than large vertebrate grazers) to control problematic plants. The study was in a fen meadow.
- Plant community composition (1 study): One controlled, before-and-after study in a fen meadow in Belgium found that introducing a parasitic plant altered the overall plant community composition.
- Vegetation cover (1 study): The same study found that introducing a parasitic plant reduced cover of the dominant sedge but increased moss cover.
- Overall plant richness/diversity (1 study): The same study found that introducing a parasitic plant increased overall plant species richness.
This section considers biological control: controlling problematic organisms by managing their enemies. Typically, this involves releasing natural enemies of target problematic organisms, such as microorganisms (e.g. a virus or a fungus), insects or parasitic plants. More enemies usually equals more damage to the target organisms. Biological control could be particularly effective for non-native problematic plants: their success in their new range may be due to escape from natural enemies in their native range (Keane & Crawley 2002).
Caution: Organisms introduced for biological control can themselves become problematic pests (e.g. the harlequin ladybird; Roy et al. 2016) or could damage non-target plants. Introductions should not be carried out without thorough assessment of likely negative impacts, non-target effects and effectiveness of control.
Key peatland types where this action may be appropriate: bogs, fens/fen meadows, tropical peat swamps.
Keane R.M. & Crawley M.J. (2002) Exotic plant invasions and the enemy release hypothesis. Trends in Ecology and Evolution, 17, 164–170.
Roy H.E., Brown P.M.J., Adriaens T. et al. (2016) The harlequin ladybird, Harmonia axyridis: global perspectives on invasion history and ecology. Biological Invasions, 18, 997–1044.
Supporting evidence from individual studies
A controlled, before-and-after study in 1994–2012 in a degraded fen meadow in Belgium (Decleer er al. 2013) found that a plot sown with parasitic marsh lousewort Pedicularis palustris developed a different plant community to unsown plots, less dominated by acute sedge Carex acuta, and with greater moss cover and more plant species. After six years, plots with and without lousewort contained a significantly different overall plant community (reported as a statistical model result). The plot with lousewort contained less acute sedge than the plot without lousewort: less biomass (80 vs 540 g/m2), shorter plants (100 vs 40 cm) and less cover (after 18 years; 20 vs 80%). After six years, the plot with lousewort also contained less overall plant biomass (460 vs 670 g/m2), but greater moss cover (49 vs 6%) and more plant species (21 vs 14 species/400 m2). Before intervention, vegetation was similar in both plots (acute sedge biomass: 870 g/m2; acute sedge cover: 100%; overall plant biomass: 960 g/m2; other data not reported). In July 1994, one 20 x 20 m plot dominated by acute sedge was sown with 500 lousewort seeds. An adjacent plot was not sown and lousewort plants were continually removed. Biannual mowing had been resumed in 1992. Data were recorded in each plot in 1994, 2000 and 2012: height of 30 random sedge plants, dry above-ground biomass from six 1 m2 quadrats, and plant species and moss cover in ten 1 m2 quadrats.