Influence of floral resource plants on control of an armored scale pest by the parasitoid Encarsia citrina (Craw.) (Hymenoptera: Aphelinidae)

• DOI: 10.1016/j.biocontrol.2005.10.009
• Publication Date: 2005-12-03T12:17:04Z
• Authors: Eric J. Rebek; Clifford S. Sadof; Lawrence M. Hanks
• Keywords: Aphelinidae; Diaspididae

We tested the hypothesis that control of an herbivorous pest would be improved by providing Xoral resources for adult natural enemies. The herbivore was euonymus scale, Unaspis euonymi (Comstock) (Homoptera: Diaspididae), a serious pest of woody ornamental plants. The experimental landscape consisted of 3 £ 3 m plots, each containing a central bed of Euonymus fortunei (Turcz.) that was infested with the scale. Floral resource plants were cultivars of four species that overlapped in bloom periods to provide a continuous supply of Xoral resources during summer: Trifolium repens L., Euphorbia epithymoides L., Coreopsis verticillata L. var. ‘Moonbeam,’ and Solidago canadensis L. var. ‘Golden Baby.’ Plots contained either low or high densities of all four species, or no resource plants. Densities of euonymus scale were typically lower in plots containing resource plants than in plots without them. Parasitism by Encarsia citrina (Craw.) (Hymenoptera: Aphelinidae) was rarely inXuenced by the experimental treatments, Xower biomass, whole-plant biomass, or scale density, but in some cases was inversely correlated with density of scales within a generation and in the subsequent generation. Parasitism occasionally reduced densities of scales in plots containing resource plants, but this eVect apparently was related to vegetative, not Xoral qualities of plants. A steady increase in parasitism rate over the three-year course of the experiment across the entire landscape was associated with decreasing density of scales, suggesting a numerical response by the parasitoid population. These Wndings suggest that the parasitoid is capable of eVectively controlling euonymus scale in ornamental landscapes where environmental conditions are favorable.