Edyta Górska-Drabik

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 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.

The role of selected plant metabolites in host plant choice by caterpillars of Acrobasis advenella (Zincken, 1818) (Lepidoptera, Pyralidae)

Abstract Acrobasis advenella is an oligophagous species feeding on plants of the Rosaceae family. The differences in concentrations of host plant quality components, above all primary metabolites and the presence or absence of secondary metabolites, directly affects herbivore growth and development. The objectives of this research were to determine the food preferences of 1st instar larvae according to the chemical composition of host plants. The highest acceptance of rowan in the free choice test by 1st instar larvae, as compared to hawthorn and black chokeberry, is positively influenced by the high content of total sugars and phenolic acids. The conclusion to be drawn from the results is that the differences in food choice by 1st instar larvae feeding on fruits could have been due to the different chemical compositions of the fruit.

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.