EVALUATION OF THE EFFECTIVENESS OF CHILOCORUS-KUWANAE (COLEOPTERA, COCCINELLIDAE) IN SUPPRESSING EUONYMUS SCALE (HOMOPTERA, DIASPIDIDAE)

A field experiment on the ability of a Chinese strain of Chilocorus ku wanae (Silvestri) (Coleoptera: Coccinellidae) to suppress densities of euonymus scale (Unaspis euonymi [Comstock]) (Homoptera: Diaspididae) on Euonymus spp. in southern New England was conducted from 1991 to 19 95. Observations were made at three spatial scales: (1) a set of 27 si tes, 14 of which received C. kuwanae releases and 13 served as checks, (2) a single apartment complex, with approximately 110 euonymus shrub s dispersed over 32 ha, at which a single release was made, and (3) th e statewide Massachusetts residential and commercial landscape as a wh ole. Chilocorus kuwanae suppressed U. euonymi at 9 of 14 release sites . The beetle failed to establish large populations at three sites, and at two other sites the experiment was ended prematurely by shrub remo val by owners. Of 13 check sites, nine were invaded by C. kuwanae over the course of the experiment and the beetle became abundant at three. Of the 10 check sites where C. kuwanae remained absent or rare, scale numbers increased at four locations, decreased at four, and were unch anged at two. At the 32-ha apartment site, C. kuwanae spread to 64% of all euonymus plants within 4 months and the proportion of plants with heavy euonymus scale infestations decreased hom 46 to 13% within 1 ye ar. At the statewide (MA) landscape level by 1994 no significant chang e had yet occurred in the proportion of plants with heavy euonymus sca le infestations. (C) 1998 Academic Press.