Oak - Diseases and Pests

Diseases and Pests

See also: List of Lepidoptera that feed on oaks

Sudden Oak Death (Phytophthora ramorum) is a water mould that can kill oaks within just a few weeks. Oak Wilt, caused by the fungus Ceratocystis fagacearum (a fungus closely related to Dutch Elm Disease), is also a lethal disease of some oaks, particularly the red oaks (the white oaks can be infected but generally live longer). Other dangers include wood-boring beetles, as well as root rot in older trees which may not be apparent on the outside, often being discovered only when the trees come down in a strong gale. Oak apples are galls on oaks made by the gall wasp. The female kermes scale causes galls to grow on kermes oak. Oaks are used as food plants by the larvae of Lepidoptera (butterfly and moth) species such as the Gypsy Moth, 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 as yet little understood disease of mature oaks, Acute oak decline, has been reported in parts of the UK since 2009.

Additionally, the Oak Processionary Moth (Thaumetopoea processionea) has become a serious threat in the UK since 2006. It defoliates the trees, and is hazardous to human health.

Recently, a new infestation of a hazardous moth has effected the population of oak trees in London. The oak processionary moth has been discovered but the caterpillars of this moth are especially harmful to oak trees because they eat the leaves leaving it vulnerable to other types of diseases.