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Biological invasions can cause major ecological and economic impacts. During the early stages of invasions, eradication is desirable but tactics are lacking that are both effective and have minimal non-target effects. Mating disruption, which may meet these criteria, was initially chosen to respond to the incursion of light brown apple moth, Epiphyas postvittana (LBAM; Lepidoptera: Tortricidae), in California. The large size and limited accessibility of the infested area favored aerial application. Moth sex pheromone formulations for potential use in California or elsewhere were tested in a pine forest in New Zealand where LBAM is abundant. Formulations were applied by helicopter at a target rate of 40 g pheromone per ha. Trap catch before and after application was used to assess the efficacy and longevity of formulations, in comparison with plots treated with ground-applied pheromone dispensers and untreated control plots. Traps placed at different heights showed LBAM was abundant in the upper canopy of tall trees, which complicates control attempts. A wax formulation and polyethylene dispensers were most effective and provided trap shut-down near ground level for 10 weeks. Only the wax formulation was effective in the upper canopy. As the pheromone blend contained a behavioral antagonist for LBAM, ‘false trail following’ could be ruled out as a mechanism explaining trap shutdown. Therefore, ‘sensory impairment’ and ‘masking of females’ are the main modes of operation. Mating disruption enhances Allee effects which contribute to negative growth of small populations and, therefore, it is highly suitable for area-wide control and eradication of biological invaders.

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Pinus radiata D. Don was grown on its own and with a range of densities of either buddleia (Buddleja davidii Franchet) or broom (Cytisus scoparius L.), two important forest weed species, in a field trial at Rotorua, New Zealand. Tree growth from the time of planting to age 3 was modelled as a function of tree size and a competition modifier. The competition modifier is, in effect, a multiplier that reduces tree growth according to the degree of competition defined by a competition index (CI). A range of CIs, with some sensitivity to both weed and tree growth and development over time, were individually incorporated into the modifier and evaluated. The "best" CI combined measures of weed height relative to tree height, proximity of the weed to the tree, and weed abundance, and was negatively correlated with an index of light availability. For a given value of CI, the effect on tree growth was independent of weed species. For diameter growth, the effect of CI was independent of tree age. However, for height growth the negative effect of a given CI value was much higher in year 3 than in years 1 and 2. This suggest that competition has an immediate effect on diameter but a delayed effect on height growth.