The Elongate Hemlock Scale, Fiorinia Externa Ferris (homoptera: Diaspididae): a New Look at an Old Nemesis

The elongate hemlock scale, Fiorinia externa Ferris, and a circular one, Nuculaspis tsugae (Marlatt) (Homoptera: Diaspididae) attack eastern hemlock, Tsuga canadensis Carriere in the eastern United States. They often co-exist with hemlock woolly adelgid, Adelges tsugae Annand, and hasten the decline of hemlock. Aspidiotiphagus citrinus Craw (Hymenoptera: Aphelinidae) was the only parasitoid species recovered from emergence cages or observed during microscopic examination of samples taken from five hemlock forests in Connecticut and one in New York during 2001. Parasitization rates of F. externa by A. citrinus were highly variable at all six sites. In Connecticut, parasitization on new needles (indicative of 2001 parasitoid activity only) averaged 6.3% (range 3.4% to 9.4%) and on old needles (indicating cumulative parasitoid activity during the past two years) averaged 16.2% (range of 10.2% to 24.2%). Parasitization rates of F. externa were substantially higher at the site in New York (18.6% and 40.6% for scales on new and old needles, respectively). These levels of parasitization are similar to those reported in Connecticut decades ago and are insufficient for biological control of F. externa. Larvae and adults of C. stigma and unidentified lacewing species were collected at each site, but in insufficient numbers to suggest their importance in biological control at this time. No pathogens of F. externa or N. tsugae have previously been reported. Microscopic examination of samples collected from 20 trees along a 2.5 km transect through the hemlock forest at Mianus River Gorge Preserve in Bedford, New York on 31 October 2001 revealed that an unknown fungal pathogen has established an epizootic on F. externa and on N. tsugae. The highest infection rates observed for F. externa on the new needles (indicative of 2001 fungal activity only) and the old needles (indicating cumulative fungal activity during the past two years) were 13% and 27%, respectively. Infection rates for N. tsugae were 7.5% and 43.0% on new and old needles, respectively.