Izabela Kot

The effect of a mealybug infestation on the activity of amino acid decarboxylases in orchid leaves

Changes in the activity of lysine decarboxylase (LDC), tyrosine decarboxylase (TyDC), and ornithine decarboxylase (ODC) within orchid (Phalaenopsis × hybridum ‘Innocence’) leaves, infested by two mealybug species: Pseudococcus longispinus (Targ. Tozz.) and Pseudococcus maritimus (Ehrh.) were quantified. The pattern of changes was dependent on the insect species and duration of infestation. P. longispinus feeding increased LDC and TyDC activity after one week during the total period of observations. This species inhibited ODC activity after one week but increased later. P. maritimus decreased LDC activity in orchid leaves at all studied terms. TyDC action also went up during the first week of the infestation and was reduced after two weeks, while ODC was decreased after one day and induced later. The mechanism for the participation of analysed amino acid decarboxylases in local and/or systemic steps of orchid responses to mealybug infestation is discussed.

Physiological Response of Pedunculate Oak Trees to Gall-Inducing Cynipidae

Abstract Gall-inducing Cynipidae (Hymenoptera) manipulate the leaves of their host plants and induce local resistance, resulting in a diversity of physiological changes. In this study, three gall morphotypes caused by the asexual generation of Cynips quercusfolii L., Neuroterus numismalis (Fourc.) and Neuroterus quercusbaccarum L. (Hymenoptera: Cynipidae) on pedunculate oaks (Quercus robur L. (Fagales: Fagaceae)), were used as a model to examine physiological alterations in galls and foliar tissues, compared to non-galled tissues. Our goal was to investigate whether plant physiological response to insect feeding on the same host plant varies depending on gall-wasp species. In particular, the cytoplasmic membrane condition, hydrogen peroxide (H2O2) concentration and changes in antioxidative enzyme activities, including guaiacol peroxidase (GPX) and ascorbate peroxidase (APX) were examined in this study. All cynipid species increased H2O2 levels in the leaves with galls, while the level of H2O2 in galls depended on the species. The presence of galls of all species on oak leaves caused an increase of electrolyte leakage and lipid peroxidation level. A significant induction of GPX activity was observed in the leaves with galls of all species, indicating stress induction. Conversely, the decrease in APX activity in both leaves with galls and galled tissues exposed to feeding of all cynipid species.

Physiological Response of Orchids to Mealybugs (Hemiptera: Pseudococcidae) Infestation

Abstract The harmfulness of mealybugs resulting from sucking plant sap, secreting honeydew, and transmitting plant viruses can give them the status of serious pests. This study documents the influence of Pseudococcus maritimus (Ehrhorn) and Pseudococcus longispinus (Targioni Tozzetti) infestation on alterations in selected physiological parameters of Phalaenopsis x hybridum ‘Innocence’. The condition of the cytoplasmic membranes was expressed as the value of thiobarbituric acid reactive substances. We have determined changes in the activities of catalase and guaiacol peroxidase and measured the following chlorophyll fluorescence parameters: maximum quantum yield of photosystem II (Fv/Fm), effective quantum yield (Y), photochemical quenching (qP), and nonphotochemical quenching (qN). The strongest physiological response of orchids was recorded in the initial period of mealybugs infestation. Prolonged insect feeding suppressed lipid peroxidation, peroxidase and catalase activity, as well as photosynthesis photochemistry. The pattern of changes was dependent on mealybug species. This indicated the complexity of the processes responsible for plant tolerance. Data generated in this study have provided a better understanding of the impact of two mealybug species infestation on Phalaenopsis and should be useful in developing pest management strategies.

Parasitoid complex associated with the overwintering generation of Swammerdamia pyrella (Lepidoptera: Yponomeutidae) in Poland.

Abstract The study was conducted on fruit trees where bands of corrugated cardboard were attached around the trunks of the trees, which were used to catch the larvae of overwintering generation of the rufous-tipped swammerdamia moth, Swammerdamia pyrella (Villers) (Lepidoptera: Yponomeutidae). Twenty-five species of parasitic Hymenoptera have been described from S. pyrella in Poland including the report in this article of seven species belonging to the family of Ichneumonidae (three species) and superfamily Chalcidoidea (four species). The parasitoids Gelis agilis F. (Ichneumonidae), Chrysocharis aquilegiae (Erdös) (Eulophidae), Catolaccus ater (Ratzeburg) (Pteromalidae), and Eupelmus urozonus (Dalman) (Eupelmidae) had not been reported from the host before. Triclistus pallipes Holmgren (Ichneumonidae), Dibrachys cavus Walker (Pteromalidae) had the greatest effect on the natural regulation of S. pyrella population. Parasitization for the wintering cocoons of S. pyrella changed each year, but it was high throughout the study. The contribution of secondary parasitoids was much higher than primary parasitoids.