Edmunds, G.F., & Allen, R.K. 1958 Comparison of black pine leaf scale population-density on normal ponderosa pine and those weakened by other agents.. Proceedings of the Tenth International Congress of Entomology. Vol. 4. Ottawa 1115 pp.

Notes: [Conference held August 17-25, 1956 in Montreal, Canada] A study of an infestation of black pine leaf scale, Nuculaspis californica (Coleman), on ponderosa pine revealed a direct correlation between the degree of damage to the tree and the population-density of the scale insects.