EFFECT OF EUONYMUS SCALE (HOMOPTERA, DIASPIDIDAE) ON EUONYMUS SPP. SURVIVAL IN SOUTHERN NEW-ENGLAND, WITH ESTIMATES OF ECONOMIC COSTS OF PEST DAMAGE

In the landscape in southern New England, Euonymus fortunei (L.) tagge d plants heavily infested with euonymus scale, Unaspis euonymi (Comsto ck), suffered 12.1% mortality annually, a 4-fold increase compared to noninfested or less infested plants. Of 3,549 landscape euonymus plant s in Massachusetts examined from 1989 to 1992, 20.9% had heavy scale i nfestations. Statewide surveys in 1992 and 1993 in Massachusetts found euonymus plant densities of 0.66 plants per commercial and 0.49 plant s per residential property. Using federal census data (1990) indicatin g that there were 90,896 commercial and 1,622,900 residential properti es in Massachusetts, the number of euonymus plants in Massachusetts wa s calculated as approximately 821,846. Because 20.9% (171,766) of thes e plants are heavily infested and therefore at increased risk of morta lity from euonymus scale, an estimated 15,803 euonymus plant deaths ca n be attributed to euonymus scale annually in Massachusetts (after all owance for mortality rates in uninfested or less infested plants). Ann ual economic losses from euonymus scale in Massachusetts (at $22.50 pe r replacement plant) are therefore approximately $355,568, or for sout hern New England as a whole, approximately $711,135.