Pasture pests are often held in check by natural enemies
but we have observed that severe pest attack over a wide
area can occur after large scale land use change. Data
were reviewed from current projects and databases for
pest density and damage records covering the past 30
years. The focus was on areas where large scale land
change has been implemented, including new irrigation
schemes, pasture development from tussock or scrub,
and land moulding for drainage via “flipping” or “hump
and hollow”. In these situations, pest outbreaks reached
unprecedented levels, e.g. 2200 grass grub larvae/m² in
the Amuri irrigation scheme, 770 porina larvae/m² on
the East Otago Plateau and 3500 manuka beetle larvae/
m² at Cape Foulwind on the West Coast. With major
land use change, a new environment is created where
pest species are provided abundant resources and the
initial invaders multiply rapidly, free from the pressure
of natural enemies. Monitoring systems, to provide
early warning of pest attack, and remediation strategies
can be used to overcome damage by these pests.[Show full abstract]
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