The Spruce Budworm, Choristoneura Fumiferana

02-01370 Spruce Budworm Bro 10/10/02 11:09 AM Page 1 MORE INFORMATION The he spruce budworm, Choristoneura fumiferana For more information on Spruce Budworms call: The Tree Line Spruce (Clemens), is the most destructive and widely (204) 945-7866. Or write: Budworm distributed forest defoliator in North America. Manitoba Conservation Forestry Branch In Manitoba T Forest Health and Ecology The destructive phase of this pest is the larval or caterpillar 200 Saulteaux Crescent Winnipeg, Manitoba R3J 3W3 stage. Massive budworm outbreaks occur periodically, Web site: www.gov.mb.ca/natres/forestry/ destroying hundreds of thousands of hectares of valuable fir and spruce. Aerial view of budworm damage In eastern Canada the budworm’s preferred food is balsam fir, Photos courtesy of Canadian Forest Service, Great Lakes Forest Research Centre, white spruce and red spruce. In Manitoba, the budworm Sault Ste. Marie, Ontario and Northern Forest Research Centre, Edmonton, Alberta. feeds primarily on white spruce and balsam fir, and, less frequently, on black spruce. 02-01370 Spruce Budworm Bro 10/10/02 11:09 AM Page 2 DESCRIPTION OF LIFE STAGES LIFE CYCLE DAMAGE CONTROL The adult moth has a wingspread of The female moth lays In light and moderate infestations Various insecticides are used 21 to 30 mm. It is grey-brown in its eggs in July on the damage is restricted to a partial against the spruce budworm to colour with silvery white patches on underside of needles. loss of new foliage, particularly in protect valuable spruce and fir the forewings. Normally, the eggs the upper crown trees. Large-scale chemical and hatch in 10 days. of the tree. biological control operations are Adult moth Light green eggs are deposited on (Not actual size) the underside of needles in elongate The tiny larvae spin Repeated loss carried out aerially in various parts 1 masses consisting of two to 60 silken covers called of new foliage of Canada to reduce tree mortality. eggs. Eggs are laid in two “hibernacula” under buds and in over a number Currently, registered products 2 rows, which overlap like bark crevices. The larvae molt to of years results to control spruce budworm in Egg mass the second instar and remain in the in reduced vigor commercial aerial operations the shingles on a roof. (Not actual size) shelter until the following spring. of the trees. include the biological insecticide They emerge with the warm These weakened trees become Severe budworm Bacillus thuringiensis (Bt), a defoliation A mature weather in early May just prior to more susceptible to secondary naturally occurring bacterium, and larva is bud expansion. Larvae mine old insects and diseases. During severe Tebutinozide (Mimic), a growth about needles, unopened buds or, when persisting infestations all of the new regulator hormone. 20 to 23 mm long. available, staminate foliage plus some old foliage may Ground spray equipment is often Its head is dark brown. flowers. Later they be destroyed for several successive used when spraying ornamentals Rows of small pale spots feed in the expanding years. Vegetative buds and devel- around the home or cottage. are present on the back buds and as the new shoots oping shoots may be killed in Currently, registered products for of the dark greenish-brown grow, they spin fine silk threads their formative stages. domestic use include malathion, body. There are six and among the needles and between Branch and top carbaryl, dimethoate, permethrin, sometimes seven stages called shoots. During epidemic popula- mortality of white acephate, aminocarb, trichlorfon “instars” during larval development. tions, old foliage will also be eaten spruce results and Bacillus thuringiensis. The pupa is pale green when first once all new foliage has been after three to formed. Later it turns reddish- consumed. The needles are seldom four years of Insecticides are applied when larval brown and is about 12 mm long. completely consumed, but are severe infestation. development has reached third to fourth instar (approximately six often clipped at the base and 3 Complete tree webbed together. Heavy feeding mortality can often to 10 mm in length), in synchrony Mature with the elongation and flaring gives trees a scorched appearance in larva occur following five to six years of Pupa mid-summer. Feeding is completed (Not actual size) severe infestation. Balsam fir, pos- open of current shoots. At this (Not actual size) in approximately five weeks sessing less foliage than spruce, may point, larvae are exposed and 4 depending on weather conditions. be killed after three years of severe vulnerable to the insecticide. Adults emerge in early July, mate, feeding damage. Successful application controls the and lay their eggs. There is only larvae before they reach the fifth one generation per year. and sixth instars, when the majority of feeding takes place..

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