DOI: 10.5061/dryad.0cfxpnvzq
title: Data from: Comparing biocontrol and herbicide for managing an invasive non-native plant species: efficacy, non-target effects and secondary invasion

description: 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.
description: This dataset if from 5-year field trial compared two
 stakeholder-selected control methods for heather <em>Calluna
 vugarus</em>, 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 <i>Lochmaea suturalis </i>(Coleoptera:
 Chrysomelidae). Data include percentage cover of heather and competing
 plant species and species richness within the study plots
 Twenty-four 5 × 5 m plots (six blocks of four plots) were located
 around the periphery of a developing heather beetle outbreak at 39° 21’
 57.3” S, 175° 42’ 55.1” E during November 2007. In each block one plot was
 randomly assigned to one of four treatments; 1. Control (insecticide spray
 to protect vegetation from beetle feeding), 2. Biocontrol (to expose
 heather to beetle feeding only), 3. Herbicide (herbicide + insecticide to
 protect vegetation from beetle feeding but expose it to herbicide), and 4.
 Biocontrol + herbicide (to expose vegetation to beetle feeding and
 herbicide). The
 herbicide used was Pasture Kleen® @ 6.5ml/L applied in December 2007 and
 2008 to match the method being employed by the NZ Defence Force (NZDF)
 within the WMTA. The insecticide used was a synthetic pyrethroid Karate
 Zeon @ 1ml/15L + 0.3ml/L Vapor Guard, which was found to successfully
 eliminate beetles from treated plots. A concurrent insecticide check
 experiment at a locality where heather beetle was absent indicated that
 insecticide did not directly affect plant cover or species richness
 (Appendix 1 SI). Insecticide applications were made in 2007 (November),
 2008 (January, February, March, September, October (twice), December),
 2009 (January, February, September), 2010 (October), and 2011 (October).
 The frequency was reduced over time because, after the feeding front of
 heather beetles had moved well past the plots, there was less re-invasion
 of the plots by beetles. Herbicide and insecticide were applied
 separately, mostly on different dates, to a 7 × 7 m area to avoid edge
 effects, with a minimum buffer of 3 m to the edge of the next 7 × 7 m
 treatment area. On the one occasion when herbicide and insecticide were
 applied on the same date, the first application was allowed to dry before
 the second application. Both herbicide and insecticide were applied to
 run-off. Plots not treated with herbicide or insecticide were sprayed with
 water to run-off on the same dates the chemicals were applied. The
 insecticide treatment was found to be highly effective at reducing
 defoliation of heather (Appendix 2 SI). Absolute percentage of cover all
 vascular and non-vascular (bryophytes, clubmosses and lichens) plant
 species was assessed visually in four 50 × 50 cm subplots, one in each
 plot corner, between the 1<sup>st</sup> and
 12<sup>th</sup> February in each of 2008, 2009, 2010, and
 2012.
description: We conducted repeated measures ANOVAs on the data. Percentage
 cover ("Raw cover data" worksheet) was converted to proportions
 and analysed for heather, clubmosses, lichens, and bryophytes, and cover
 and species richness were analysed for summed groups of native dicots,
 native monocots, non-native dicots (excluding heather) and non-native
 monocots. To avoid pseudoreplication, the average cover across the four
 quadrats (se, ne, nw, sw)  per plot in the "Raw cover data" was
 analysed and the total number of plant species in all four quadrats was
 summed in the species richness analysis.