Data from: Comparing biocontrol and herbicide for managing an invasive non-native plant species: efficacy, non-target effects and secondary invasion

1. Globally, invasive non-native plants are an increasing threat to
indigenous biodiversity and ecosystems, but management can be compromised
by poor efficacy of control methods, harmful non-target effects or
secondary invasions by other non-native plant species. 2. A 5-year field
trial compared two stakeholder-selected control methods for heather, a
European plant invading native ecosystems in and adjoining Tongariro
National Park in New Zealand. The control methods were a selective
herbicide (Pasture Kleen®; 2,4-D ester) and biocontrol with an introduced
beetle Lochmaea suturalis (Coleoptera: Chrysomelidae). 3. Biocontrol
reduced mean heather cover by 97%, slightly more than herbicide at 87%,
compared with a 20% increase in heather under no management. 4. Cover of
native dicots, the most species-rich plant group, increased following
biocontrol. In contrast, herbicide application had major non-target
effects on native dicots, reducing their percentage cover and species
richness. Native monocot cover and species richness increased following
both herbicide and biocontrol treatments. 5. A similar 8-fold increase in
non-native monocots occurred following both biocontrol and herbicide
treatments. Overall, secondary invasion was greatest with biocontrol
because non-native dicot cover also increased, whereas herbicide almost
eliminated non-native dicots. 6. Synthesis and applications. Biocontrol
and herbicide treatments both controlled heather but herbicide application
was associated with severe non-target impacts on native dicots. Benefits
to the native flora were consequently greatest in the biocontrol
treatment, despite greater secondary invasion. Control strategies for
management of widespread non-native plants to optimize ecosystem outcomes
should include more consideration of biocontrol.