Quantifying the economic cost of invertebrate pests to New Zealand’s pastoral industry

Abstract

Two exotic pests, Argentine stem weevil (ASW) and clover root weevil (CRW) are causing damage estimated at up to $200 M p.a. and $235 M p.a. respectively in dairy and sheep and beef pastures. While CRW is subject to successful biological control management it still causes considerable losses. Lesser pests also contribute to lost production, particularly as they often coexist with more major pests. However, their economic cost to New Zealand is difficult to calculate due to the variable nature of infestations on both temporal and spatial scales. At farm and paddock level, it is abundantly clear that substantial savings could be made if pest management is achieved. It is equally clear that in many instances the tools to do so are limited but if developed would contribute substantially to farm profitability.

Development of a Yersinia entomophaga bait for control of larvae of the porina moth (Wiseana spp.), a pest of New Zealand improved grassland systems

“…The bait treatment reduced the porina population to less than 20 larvae per m 2 , a population density predicted to be below the threshold for pasture damage . Larval densities of 20–40 porina per m 2 caused the same reduction in DM as one ewe with lamb . However, in the control plots, the mean density of approximately 50.4 ± 5.71 larvae per m 2 (Table ) remained at economically significant levels.…”

“…Adult eclosion is strongly influenced by climate. Adult emergence is generally synchronised so that peak flight periods occur for most species and haplotypes . The adults do not feed and live only a few days.…”

“…The adults do not feed and live only a few days. The time of these peaks varies with species, haplotype and location . W. signata and W. umbraculata emerge over longer periods and peaks are less obvious for these species.…”

“…The females fly at least several hundred metres (possibly much longer) indiscriminately scattering eggs over vegetation. Each female can produce over 3000 eggs . For both species the time taken for the eggs to hatch varies between species and with temperature, but in pasture is generally between 3 and 6 weeks.…”

“…However, initial investigations of larval populations in pasture suggest that W. copularis (early-and late-flying haplotypes) is the most common and widespread species, followed by W. cervinata. 6,8 Several species (W. jocosa, W. mimica and W. fuliginea) may be locally important, particularly in the southern South Island, 6 but others such as W. signata and W. umbraculata are rarely found in pasture.…”