Canadian Forest Service Publications

Mortality and height growth losses of coniferous seedlings damaged by the black army cutworm. 1992. Maher, T.F.; Shepherd, R.F. Canadian Journal of Forest Research 22: 1364-1370.

Year: 1992

Issued by: Pacific Forestry Centre

Catalog ID: 3150

Language: English

Availability: PDF (download)

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Abstract

Growth and survival of seedlings were determined for 1 to 3 years following defoliation by black army cutworm, Actebia fennica (Tausch.). Ten data sets were collected on three sites and included four species of seedlings: interior Douglas-fir, Pseudotsuga menziesii var. glauca (Beissn.) Franco; lodgepole pine, Pinus contorta Dougl.; western larch, Larix occidentalis Nutt.; and Engelmann spruce, Picea engelmannii Parry. Mortality following defoliation cannot be assessed until after the flush in the next growing season because completely defoliated seedlings often regenerate new foliage and survive. More than 90% of the total mortality that did occur was detected at that time. Mortality of up to 39% occurred when seedlings were defoliated more than 60%; most of this occurred when planting was carried out concurrent with defoliation. Synergistic root stress effects caused by poor planting, dry sites, or drought significantly increased mortality. Height growth was significantly reduced when defoliation was greater than 60%; the greatest effects occurred when terminal bud destruction accompanied needle loss. Growth losses were greatest the year of defoliation; recovery of height growth of lodgepole pine was complete by the 2nd year on good growing sites. On poor sites, retardation of lodgepole pine height growth was still evident after 3 years.