Eradication techniques for invasive Berberis aquifolium in coastal dunes (Belgium)

Non-native Berberis aquifolium is notoriously invasive in Belgian coastal dunes. With
its strong clonal growth through suckers, this evergreen shrub outcompetes native
species and affects dune succession. To prevent further secondary spread and
mitigate its impact, there was an urgent need for knowledge on the effectiveness of
control measures, both at the level of individual plants as on habitat level. Here, we
report on two removal experiments. First, small Berberis clones were subjected to one
of four treatments (manual uprooting, foliar herbicide application, stem cutting followed
by herbicide or salt application), with regrowth being monitored up to one year after
treatment. Plants proved most susceptible to foliar herbicide application (5%
glyphosate solution), resulting in 77% of the clones apparently killed. Second,
mechanical removal using a heavy excavator was applied in a highly infested area
(350 m², with nearly 100% Berberis cover) and accompanied by manual removal of
smaller rhizome/stolon fragments. The action was documented in detail and the
outcome monitored in terms of regrowth from different depths. The rooting system
appeared to be relatively shallow (30-40 cm). The limited regrowth from superficially
buried rhizome fragments could easily be pulled out. We present some guidelines that
may serve as a starting base for future control, and may become further refined as
experience builds up.