Obtained research results will contribute to a more adequate production of high quality healthy food, to the increase of productivity and economy of production and to the decrease of negative influence of agriculture on the environment. They will also contribute to a more intensive development of integrated pest management in Slovenia including the introduction of certain forms of biotic plant protection. While studying problems of harmful organisms we have paid special attention to the development, introduction and use of new detection methods for identification of fungi, viruses, viroids, bacteria and nematodes. Among others the paraquat test and PTA-ELISA with bioamplification for Colletotrichum acutatum, Duncan's test for Phytophthora fragariae var. fragariae, DAS-ELISA and nested PCR for BNYVV, PCR for PPV, isolation of bacteria on selective media, cultivation methods for bacteria identification, determination of presence of plasmid genes tmr, acs and vis with PCR and determination of opines with high-voltage paper electrophoresis for Agrobacterium sp., Biolog for identification of gram negative bacteria, PCR for Globodera rostochiensis and for Bursaphelenchus xylophilus, isozyme gel electrophoresis (PhastSystem) for Meloidogyne spp. and ITS-RFLP for Xiphinema rivesi were introduced to our laboratories. The detection methods introduced are a basis for further study of spreading and ecology of harmful organisms, interspecific variability of some organisms, problems of use of plant protection products and its consequences and the factors influencing negative trends in the Slovene agricultural area. Better knowledge of spreading of harmful organisms will contribute to a more successful assessment of their potential danger. Methods for determination of residues of active substances of plant protection products in agricultural products were developed, which will serve for their successful surveillance. The results of the research done in frame of the study of agricultural area will contribute to a better utilisation of production potential, preservation of cultivated landscape and a more expedient planning of land-use.