Canadian Forest Service Publications
Relationships between yellowheaded spruce sawfly, Pikonema alaskensis, density and defoliation on juvenile black spruce. 2006. Johns, R.C.; Ostaff, D.P.; Quiring, D.T. Forest Ecology and Management 228: 51-60.
Available from: Atlantic Forestry Centre
Catalog ID: 26216
Manipulative field experiments and field surveys were carried out to evaluate the relationship between the density of yellowheaded spruce sawfly, Pikonema alaskensis (Roh.), and resultant defoliation on young open-grown black spruce, Picea mariana (Mill.) B.S.P., in central Newfoundland. In sleeve-cage experiments, the number of early and late-instar larvae per current-year shoot explained greater than 73 and 69%, respectively, of variation in mid-crown branch defoliation and 34–75% of variation in leader defoliation. In field surveys, densities of eggs, mid- and late-instar larvae in whorls 2 and 4 explained greater than 34, 46, and 75% of variation, respectively, of defoliation in leaders and in whorls 1 and 2 of black spruce. Estimates of adult femail and male abundance obtained from sticky traps explained 66 and 40% of variations, respectively, in defoliation among trees within stands and almost 90% of variations in defolation among stands. Relationships were slightly improved by incorporating previous defoliation into analyses as a covariate. Our results indicate that density–defoliation relationships for all stages of P. alaskensis on black spruce are robust and suitable for incorporation into a management program for this pest.