Canadian Forest Service Publications
Sequential sampling plan with two critical levels for spruce bud moth (Lepidoptera: Tortricidae). 1988. Régnière, J.; Boulet, B.; Turgeon, J.J. Journal of Economic Entomology 81: 220-224.
Issued by: Laurentian Forestry Centre
Catalog ID: 14421
Availability: PDF (request by e-mail)
A sequential sampling plan, based on Iwao's method, is described for population surveys of the spruce bud moth, Zeiraphera canadensis Mutuura & Freeman, in plantations of white spruce, Picea glauca (Moench) Voss. The plan segregates larval populations into three density classes distinguished by critical levels of two and eight larvae per sample branch at a 68% confidence level. Unrealistically high sample sizeswould be required to achieve the more common levels of 90 or 95% in an insect survey context. The sampling plan's performance in terms of average number of samples required, time consumption, and error rates was assessed by computer simulation and field tests. Average sample sizes attained 20 branch tips at densities near the lower critical level but remained near or below 10 at most densities. Time consumption was a function of sample size and insect density. The plan required, on average, 1-2 h in plantations where > 1.5 larvae per sample are present. Error rates exceeded the nominal 17.5% rate in density ranges of 1.5-3.0 and 6.5-10.0 larvae per sample.