The paper reports results of investigations concerning the influence of saponin extract of quillaja on the food choice and development of Colorado potato beetle. Choice tests with the use of potato leaf discs treated and untreated with tested saponins’ extract were made. The influence of the presence of saponins on the food choice and intensity of insect feeding were observed. It was stated that saponins significantly restrain feeding and disturb development of this pest.

The influence of saponins isolated from alfalfa (Medicago sativa L.) leaves and glucosinolates isolated from mustard (Sinapis alba L.) seeds on the fertility of Colorado potato beetles (Leptinotarsa decemlineata Say) reared on potato leaves treated with these substances was tested. It was observed that both compounds restrained the process of egg laying however, the action of saponins was stronger.

The content and composition of glucosinolates in green parts of mustard plant iSinapis alba L.), at different stages of plant development were analysed. Four mustard varieties: Salvo, Metex, Ascot and Nakielska were taken under consideration. It was stated that in green parts of mustard sinalbin was dominating component of glucosinolates, but also glucotropeolin and small amounts of glucobrassicanapin apeared. The content of these compounds changes during vegetation and it is different in particular plant organs. Biological activity of mustard glucosinolates towards cabbage aphid was also studied. The correlation between the content of glucosinolates in plant and its susceptibility to aphid iBrevicoryne brassicae L.) infestation was checked. It was found that higher level of glucosinolates in plant caused some limitation of this pest development. Also the activity of water and alcohol extracts from mustard leaves was tested in relation to cabbage aphid. Disadvantageous influence of these extracts on aphids' survival was observed and this effect depended on extracr's concentration.

The influence of glucosinolates isolated from oilseed rape seeds on the growth of pathogenic fungi infecting oilseed rape was studied. The activity of those compounds against 3 fungal species was tested in vitro. It was stated that glucosinolates present in the medium did not totally inhibit the growth of the fungi, but considerably confined the area of colonies of 2 out of 3 fungal species studied.

The influence of oilseed rape glucosinolates on the grown in vitro pathogenic fungi was studied. Two pathogenic to oilseed rape fungi species: Fusarium roseum and Rhizoctonia so/ani were taken into consideration. It was observed that glucosinolates added to the medium limited the growth of both tested fungi to some extent, especially when higher concentrations of glucosinolates was supplied.