Oak processionary these caterpillars in other areas should be reported to the Forestry Commission. The research agency of the Forestry Commission has issued guidance on the way to contain outbreaks and deal with infestations, so as not to increase the risk to the public. On 31 March 2008 an emergency amendment added the moth to the list of pests in The Plant Health (Forestry) Order 2005, and has required all oak trees coming into the UK from the rest of Europe to have Plant Passports. In 2013 the Forestry Commission announced helicopters would be deployed to "blanket spray woodland" where the caterpillars
Oak "Lymantria dispar", which can defoliate oak and other broadleaved tree species in North America. A considerable number of galls are found on oak leaves, buds, flowers, roots, etc. Examples are oak artichoke gall, oak marble gall, oak apple gall, knopper gall, and spangle gall. A number of species of fungus cause powdery mildew on oak species. In Europe the species "Erysiphe alphitoides" is the most common cause. A new and yet little understood disease of mature oaks, acute oak decline, has been reported in parts of the UK since 2009. Oak processionary moth ("Thaumetopoea processionea") has become a serious threat