Fiorinia externa and Tsugaspidiotus tsugae (Homoptera: Diaspididae): Distribution, Abundance, and New Hosts of Two Destructive Scale Insects of Eastern Hemlock in Connecticut

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Abstract
A winter survey for scale insects of Tsuga canadensis Carrière, Eastern hemlock, at 279 sites in 31 towns in Fairfield and New Haven Counties, CT, indicated that Fiorinia externa Ferris and Tsugaspidiotus tsugae (Marlatt) (Homoptera: Diaspididae) are serious pests throughout much of the area. A 3rd diaspidid scale, Phenacaspis pinifoliae (Fitch), occurred only in low densities at 4 sites and was not considered a pest of hemlock. The heaviest infestation of F. externa was in the town of Greenwich where trees at 15 of the 18 sites sampled supported high densities (>75 scales/100 needles). In the 9 towns comprising the major area infested, F. externa occurred on hemlocks at 81 of the 113 sites (71.7%) sampled. T. tsugae occurred in all 31 towns surveyed but only at 89 of the total 279 sites (31.9 %) were hemlocks infested. At one site each in New Canaan and in Westport, densities of T. tsugae were high (>75 scales/100 needles). At 58 sites, both species occurred together on the same trees and occasionally on the same needles. A survey conducted at the Montgomery Pinetum and the Bartlett Arboretum, Fairfield County, CT, revealed that F. externa and T. tsugae were able to colonize and mature on a wide variety of exotic conifers. Adult female F. externa occurred on the following conifers examined: all 9 Abies spp.; all 3 Cedrus spp.; all 12 Picea spp.; 12 of 14 Pinus spp.; Pseudotsuga menziesii Britton; both Taxus spp.; and all 4 Tsuga spp. F. externa was not observed on Pinus griffithi McClelland or on Pinus lambertiana Douglas indicating possible resistance of these pines to scale attack. Adult T. tsugae occurred on 3 Abies spp., Cedrus atlantica Manetti, 3 Picea spp., and 2 Tsuga spp.