Dothistroma needle blight (DNB) is caused by the fungus Dothistroma septosporum. It has been found on a range of conifer species, but pine are by far the most common hosts, with Corsican pine, lodgepole pine and Scots pine all now affected. Defoliation can continue year on year and gradually weaken the tree, significantly reducing timber yields and eventually leading to mortality. DNB is now widespread in all Forestry Commission districts in England and Scotland and in three out of four districts in Wales. An aerial spray trial was carried out in Scotland in 2013 using a copper-based product from New Zealand but detailed results have not been published. The use of aerial treatment in New Zealand is widespread, regular – and necessary.