insect production services. biology of the fir coneworm...
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Insect Production Services
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Biology of the Fir Coneworm(Dioryctria abietivorella)
IntroductIonThe fir coneworm, Dioryctria abieti-vorella is found throughout most of North America. They are members of the Pyralidae family, better know as snout nosed moths. The larvae feed on a variety of conifers includ-ing Douglas fir, balsam fir, grand fir, subalpine fir as well as spruces, pines, larches, and hemlocks. Fir coneworm were first recorded in Canada in 1939 with outbreaks occurring as local infestations within Ontario and Quebec. These local infestations usually occur at tree nurseries, plantations and cone-seed orchards.
LIfe cycLeIn Canada, fir coneworm typically have only one generation per year but development is not well synchronized and larvae are found in cones from spring to fall. They have a faculta-tive diapause, which is induced by photoperiod or length of daylight. Fir coneworm over-winter as fifth-instars within a hibernaculum spun in the duff layer on the ground. In the spring, still within the duff, the larvae moult into pupae, which are amber to reddish-brown in colour and about 11.0 mm long. Adults emerge a few weeks later as grey moths with distinctive black and white transverse “w” shaped bands lo-cated at the midpoints and the tips of their narrow forewings. Their hindwings are a greyish-white with a narrow dark grey band bordering the perimeter. During the summer months, adults mate and females lay whitish-green oval eggs 1.0 mm long, near or on cones. Within about a week after they are laid these eggs mature and turn orange-red in colour. When larvae first hatch, they have yellow-amber bodies with brown heads
and it is at this stage they burrow into developing cones. As they mature, the larvae turn dark brown and develop two light colored longitudinal bands down the length of their entire body.
damage and nuIsanceFir coneworm larvae prefer to feed within cones on seeds and scales
but will also feed on terminal shoots, bark, branches and twigs. Larvae also have the capability of mining into tree trunks and branches. Signs of damage include ragged holes on the outside of cones surrounded with small amounts of frass and resinous material, mined terminal shoots, new cones stuck together with webbing and chewed needles or pitch masses at entry points on branches and trunks of trees. Fir coneworm typically do not damage trees but can pose a threat to seed and cone crops in seed orchards.
what can I do?For private landowners, controlling fir coneworm may prove difficult. The greatest problem is getting to the larvae because they stay hidden so well within cones, branches and feeding shelters. If there are small trees, few in number, manually removing and burning cones while larvae are still within them ( i.e., before September) may prove effective. Removing the top duff layer surrounding infested trees in autumn may prove effective by exposing over-wintering larvae to predation and eliminating this protection may also subject the larvae to harsher (freezing) environmental conditions, thus reducing survival over the winter.
ContactJohn Dedes, Insectarium SupervisorCanadian Forest Service, Great Lakes Forestry Centre1219 Queen Street EastSault Ste. Marie, ON P6A 2E5(705) [email protected]