**Acknowledgements**

The first appearance of cabbage flea beetles was in our research detected in the beginning of May, while cabbage stink bugs began appearing in the second half of May. The said findings are congruent with the results of bionomy of the studied groups of harmful pests in the central part of Europe. Feeding of cabbage flea beetles and cabbage stink bugs was noticed on all selected plant species. On the basis of the collected data, we have found out that cabbage stink bugs display particular preference to feeding on oilseed rape, while cabbage flea beetles were

The trap crop method that we studied in our research will be feasible especially in the systems of mid-late cabbage production. The average mass of cabbage was influenced primarily by the selection of a hybrid. Mid-late hybrid 'Hinova' in our research proved to be more productive

On the basis of our research results, which were obtained at two different locations, we can conclude that air temperature has an important effect on the extent of damage by cabbage flea beetles on Brassicasas. Rising average daily temperature of air caused higher extent of damage

The different preferences of the studied groups of harmful pests are conditioned also by natural resistance of plants. One of the factors of natural resistance in Brassicas is also glucosinolate content. Glucosinolates in our research proved to be an important, yet variable factor of natural resistance of Brassicas to attacks by cabbage flea beetles and cabbage stink bugs. We found out that variability of glucosinolates was conditioned by plant species, and the content of these substances differs considerably also between different organs of the same plant species. Our research also revealed variability in the content of glucosinolates between individual geno‐ types of the same plant species, i.e., between individual genotypes of cabbage. In the samples of oilseed radish, we detected the largest amount of glucoraphanin (8.66±1.81 μmol/g mass of dry seed); sinalbin was present in the significantly largest amount in the samples of oilseed rape and white mustard. Although the analysis confirmed sinalbin as the most frequent glucosinolate in the samples of white mustard, the further analysis of the data revealed weak correlation (*r* = 0.36) between its content versus Brassicas and the content of damage by cabbage

Sampling of different plant parts showed that the content of certain glucosinolates, for example glucobrassicin and glucoraphanin in blossoms of oilseed radish or sinalbin and epiprogoitrin in blossoms of white mustard, is much higher than in the leaves of the studied plant species. We found out that cabbage flea beetles were at the time of blossoming very intensively feeding

We have found out that glucosinolate content in plants is influenced primarily by temperature extremes. The results of past studies concerning activities of these secondary metabolites support the notion that they act in a manner that is specific for an individual group of these secondary metabolites. However, we found out that there are differences in their activities also within individual groups of glucosinolates. Glucobrassicin, the only detectable glucosinolate in all studied plant species, belongs to indole glucosinolates. We have found out that this glucosinolate in oilseed radish affects negatively the extent of damage by the species from the

feeding mostly on oilseed radish, which proved the most attractive host for them.

and consequently more suitable for production in our growth conditions.

by cabbage flea beetles on the studied species of Brassicas.

stink bugs on them.

432 Insecticides Resistance

on plants of white mustard and oilseed radish.

This chapter was performed within P4-0013, a program funded by the Slovenian Research Agency. Part of the researchers presented in this chapter was performed within Professional Tasks from the Field of Plant Protection, which are funded by the Ministry of Agriculture, Food, and Forestry of the Republic of Slovenia, Administration of the Republic of Slovenia for Food Safety, Veterinary Sector and Plant Protection. Authors are thankful Dr. Iztok Jože Košir for chemical analysis of Brassica leaves.
