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The distinctive caterpillars of this moth feed on a wide range of shrubs and trees but they are rarely present in sufficient numbers to cause significant problems.
Vapourer moth (Orgyia antiqua) female laying eggs.
Vapourer moth, also known as rusty tussock moth, are sexually dimorphic (males and females are different in appearance as adults). The males have plain orange-brown wings (wingspan 25-30mm) with a white spot near the trailing edge of the forewing, whilst the females have an enlarged light grey-brown body with greatly reduced wings and are unable to fly. Males are attracted to the female by a scent that she emits (sex pheromone). After mating, the female deposits her eggs over the surface of the pupal cocoon. These eggs will overwinter and hatch during the following spring.It is the caterpillars that are particularly eye-catching and it is this stage that is most often noticed in gardens. The caterpillars are predominantly grey-black with small red spots running in rows down both sides of the body; the most easily recognisable features are the four yellow tufts of hair-like setae found towards the head end.
Caterpillars cause a slight defoliation of host plants. Larval food plants include most native broadleaved trees and shrubs such as birch, blackthorn, elm, hawthorn, hazel, lime, oak and willow, as well as many cultivated plants including cotoneaster and pyracantha. In some cases evergreen trees and shrubs are eaten.The caterpillars are present on plants from late April to August and when fully grown will pupate within a silken cocoon on or nearby their host plant. The adult moths emerge August to September.
The presence of the caterpillars of this moth rarely cause significant damage in gardens and it can usually be tolerated. Caterpillars, and associated moths, are important as a food source for other garden wildlife and so should be preserved where possible.
Control measures are only required if the caterpillars are causing a significant amount of defoliation. If the caterpillars are spotted at an early stage on small plants they can be removed to a larger plant; on larger trees and shrubs whilst some parts of the plant may be defoliated this will have no effect on the long term health of the host plant and so can be tolerated. When handling the caterpillars gloves can be worn as a precaution, although the hairs are visually striking they do not usually cause irritation.If the egg-covered cocoons, on which this species overwinters, are spotted these could be removed to another host plant elsewhere in the garden.
Chemical control is rarely necessary in gardens, but if caterpillars are too numerous to be removed by hand an insecticide spray could be considered. Control can be achieved by spraying synthetic pesticides such as deltamethrin (e.g. Sprayday Greenfly Killer), lambda-cyhalothrin (e.g. Westland Resolva Bug Killer), cypermethrin (e.g. Py Bug Killer) or the organic pesticide pyrethrum (e.g. Defenders Bug Killer). The older caterpillars are more tolerant of pesticides than young larvae. These products can be used on some edible plants, check the label and ensure instructions are followed. Plants in flower should not be sprayed due to the danger to bees and other pollinating insects.
Inclusion of a pesticide product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener.
Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)
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