The aim of presented investigation was to determine the composition of scale insects species and intensity of their occurrence on some greenhouse’s ornamental plants. The investigations were carried out in the greenhouse of Maria Curie Skłodowska Botanical Garden in Lublin in years 2002–2004. Eight species belonging to seven botanical families were observed: Abutilon striatum cv. Thomsoni, Cyrtomium falcatum Presl., Dizygotheca elegantissima (Veitch), Hedera helix L., Hypoestes phyllostachya Presl., Nerium oleander L., Passiflora guadrangularia L., Ruscus aculeatus L. The quantitative analysis of the studied material was performed making use of the following ecological indicators: number and density. Identification of the scale insects species was performed on the basis of microscope slides. Three species of the scale insects belonging to three families were observed on ornamental plants: Pseudococcidae [Pseudococcus maritimus (Ehrh.)], Coccidae [Saissetia coffeae (Walker)] and Diaspididae (Aspidiotus nerii Bouchè). The scale insects were noted on all species of studied plants. Observed scale insects are typical polyphagous and all of them are considered as harmful pests in greenhouses. Among scale insects inhabiting this group of plants distinctly numerous on particular host plants were S. coffea and A. nerii. On the studied plants scale insects were stated at four degree of density.

We examined the effects of feeding by the polyphagous insect Coccus hesperidum on its host plant Nephrolepis biserrata under different intensities of infestation. As an effect of scale insect feeding there were significant changes in the values of parameters reflecting the state of cell membranes. N. biserrata plants reacted to the biotic stress by increasing guaiacol peroxidase activity and decreasing catalase activity. Our data show that these processes play key roles in plant tolerance mechanisms, here the fern’s response to insect feeding. The observed complex reaction of N. biserrata testifies to actively proceeding, complex and very often contrasting mechanisms triggered with the aim of neutralizing the effects of biotic stress and enabling normal cell functioning in plants attacked by scale insects