The potential role of aerial pesticide applications to control landscape-scale outbreaks of pests and diseases in British forestry with a focus on dothistroma needle blight

Abstract

British forestry is threatened by numerous pests and diseases. This study investigated the potential for re-introduction of aerial pesticide applications for landscape-scale disease management. In North Scotland in 2013 and 2015, copper oxychloride was applied to Pinus sylvestris L. stands infected with Dothistroma septosporum (Dorogin) Morelet. Helicopters distributed ultra-low-volume (ULV) applications of product via Micronair rotary atomisers, following methods used against D. septosporum in P. radiata D. Don stands in New Zealand. Product deposition was quantified on paper catchers and in foliage, soil and water. Catchers 100 m beyond the plot boundaries intercepted 0.5 per cent of within-plot mean deposition. Foliar analysis revealed slightly elevated copper concentrations (+0.07 μg g−1 dw) 250 m outside plot boundaries. Copper in foliage and needle litter remained above background levels for 109 and 157 weeks after application, respectively, longer than recorded during New Zealand operations. Concentrations in the soil increased over 3 years’ monitoring, whilst deposition into water traps resulted in copper concentrations well within limits set by the Scottish Environmental Protection Agency. No deleterious impacts on vascular and non-vascular ground and canopy flora were recorded. Copper fungicide applications significantly reduced foliar infection at both sites but did not affect needle retention. Further ground-based trials will investigate the efficacy of other actives. In Britain, such aerial operations have not occurred for two decades: this study demonstrated aerial and ground teams have the necessary expertise for their re-introduction, whilst highlighting areas needing further optimization.