Contribution to the Life History and Dynamics of the Pine Needle Scale, Phenacaspis pinifoliae,1 in Central New York2

Abstract

Mugho, Scots, and red pine were sampled intensively to study the population dynamics of Phenacaspis pinifoliae (Fitch). Change in population intensity in 1 year (2 generations) ranged from a decrease of 50% on 1 red pine to a 3- to 5-fold increase on 2 Scots pines and a 4- to 20-fold increase on 2 Mugho pines. Survival of scales in the spring and summer generations was strikingly different, spring crawler survival being much lower than in summer. Hatch synchrony and weather explain this difference. Host species also was an important factor in spring scale survival. Populations increased markedly on Mugho pine, remained static on Scots pine, and crashed on red pine in the spring of 1969. Survival of summer scales was not different on different pine species. Chilocorus stigma (Say) (Coleoptera: Coccinellidae) consumed many scales in all stages of development and contributed to scale population decline. But this beetle was not important in the dynamics of all scale populations that were studied. One eulophid parasite, Prospaltella bella Gahan, was a variable and important scale-mortality factor. Parasitized female scales failed to oviposit, and percent parasitism increased as scale density increased. Though parasites and predators were associated with all scale populations studied, their impact was not significant until after the economic injury level was reached.