Tools and Resources
Copper fungicides are used routinely in New Zealand to help manage Dothistroma needle blight in their pine plantations. In the summer of 2013 and 2015 Forest Research collaborated with Forestry and Land Scotland and Scottish Forestry to use a Micronair system mounted on a AS 350 B2 Single Squirrel helicopter to make Ultra Low Volume (ULV) applications of the fungicide, copper oxychloride to two areas of Scots pine forest near Inverness. These forests compartments were subsequently monitored for up to three years to determine the persistence of the fungicide and investigate DNB intensity in the treated trees. Two scientific journal articles describing the operations are provided in the Additional Resources section, below.
Large scale aerial pesticide applications have not been carried out in British forestry for two decades, and prior operations have not been well documented, leading to a loss of vital, practical knowledge. Thus, an important aim was to record our experiences to inform any future operations. Specifically, we aimed to:
Traps set up inside and outside the sprayed areas showed good on-target application, with a rapid drop-off in product deposition beyond plot boundaries, and at 100 m, deposition was only 0.5 % that measured inside the plot. Copper products persist on tree foliage for up to three to four months in New Zealand (Bulman et al., 2008), but in our study, foliar copper concentrations were still ten times higher than background levels after four months. Extending monitoring for two years showed a pronounced decline, and movement of copper from the upper levels of the tree canopy downwards, but concentrations were still significantly above background levels in the lower canopy even after this length of time.
Copper concentrations in the needle litter layer and the soil remained above background levels over three years, suggesting the product is relatively immobile in this substrate. Concentrations remained lower than EU maximum permitted concentrations (140 μg g-1; C.E.C, 1986), and at both sites were lower than average values for Scottish soils.
Our investigations indicated no visible phytotoxicity within the tree canopies or in ground-based vegetation or above and below-ground fungal communities.
The applications reduced visible signs of DNB infection but did not lead to any increases in tree canopy density over the two years of monitoring. Trees can however, take several years to recover enough for the impacts of management interventions to be detectable, so future work should include longer term post application monitoring of crown condition.
In any future work we recommend investigating other fungicidal products, as during the second application copper oxychloride was reclassified by FSC as ‘Highly Hazardous, Restricted’ and could only therefore be used for trial purposes. Ground-based trials are currently underway to investigate other compounds active against DNB.
Environmental constraints and certification standards for sustainable woodland management (e.g. ukwas.org.uk) and the Forest Stewardship Council (fsc.org/en) have encouraged a move away from use of synthetic chemical products, and very few pesticides are currently used in British forestry. Despite this, recent landscape-scale disease outbreaks in commercial plantations have renewed interest in chemical control, and the sheer scale of some outbreaks suggests aerial operations could play a significant role. Using as a model the current high profile, widely damaging, DNB, we investigated the feasibility of re-including aerial ULV applications in a forest industry toolkit.
Dothistroma septosporum, the causal agent of Dothistroma needle blight (DNB) in the UK, is a significant tree health issue within Great Britain’s commercial pine plantations and forest tree nurseries Infection causes premature defoliation, and in some cases tree mortality. Pine species vary in susceptibility and, although Corsican and lodgepole pine are very susceptible, there is increasing infection within Scots pine. Scots pine, particularly in Caledonian pine forests, is very important ecologically and culturally and so its protection is a high priority for the forest industry.
Current methods of control involve clear-felling to reduce inoculum loads, changing thinning regimes within infected stands to open-up the crop and decrease humidity, taking statutory action in tree nurseries to remove infected stock, and re-planting in the forest with less susceptible species where possible. In New Zealand however, aerial application of copper compounds is routinely carried out to manage the disease.
Copper is effective against Dothistroma septosporum as:
This experiment was set up in the summer of 2013 and 2015. Both plots were monitored for up to 3 years post application and are now closed. Two scientific papers were recently released, discussing the results obtained during these forest operations.
Tubby, K. & Forster (2021) 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. Forestry: An International Journal of Forest Research, Volume 94, Issue 3, July 2021, Pages 347–362. https://doi.org/10.1093/forestry/cpaa038
Tubby, K. & Forster (2022) High fliers: exploring the potential role of aerial fungicide operations in British forestry. Quarterly Journal of Forestry, July 2022, Vol. 116, No. 3, 184-189