The foundations for establishing and the operation of the Plant Protection Department were set up in 1898 when the then Ministry of Agriculture in Vienna, with its decision no. 22713 that was issued on 20 October, temporarily authorised the statute of the Agricultural and Chemical Test Site for the Carniola Region in Ljubljana. In the statute that was finally confirmed on 19 March 1902, it was stated that the purpose of the test site was to be an independent institute: “with strictly scientific tests is to facilitate the development of agriculture in the Carniola Region, to research and test (analyse) matters in close relation with actual agriculture as well as the associated plant diseases”. The institute, which in 1914 was renamed the Provincial Agricultural and Chemical Test Site and Animal Feed Test Site, was, before the First World War, the only research laboratory in the Carniola region that performed chemical, physiological, bacteriological and microscopic analyses and other research for the requirements of agriculture, food science and nutrition, industry and crafts. After the First World War, the patronage of the “test site” was taken over by the National Government for Slovenia, and the national assembly of the Kingdom of Serbs, Croats and Slovenes in 1919 issued the rules (12 December 1919) and act (12 February 1922) on agricultural tests and control stations based on which the institute was reorganised and renamed the Agricultural Trial and Control Station in Ljubljana. Some of the fundamental tasks of the station were researching plant diseases and pests and prescribing methods for their destruction and for protection against them. The above mentioned act prescribed that the stations must have suitable buildings, laboratories, greenhouses, test fields and other conditions. The agricultural test and control station in Ljubljana was composed of four sections (departments), of which we shall mention only the phytopathological section, which can certainly be considered the beginning of the later Plant Protection Institute. The phytopathological section was headed from 1935 to 1951 by prof. dr. Franjo Janežič. At the time, the test, research and control work was done mainly by studying of the California scale, scab, powdery mildew, black spot disease, leaf spot on endive and viruses on potato.
1953 - implementation of post-control of seed potato for virus infections, which means we have been testing the entire seed production of potato from the middle of the 20th century.
1954 - an anti-downey mildew service was established at the Agricultural Institute of Slovenia in cooperation with the Hydrometeorological Institute, which was later joined by the anti-phytophthora service.
Beginning of 1960s - start of virological research, mainly on grapevine and potato. At the time, it was discovered that the cause of the deterioration of grapevines in the Primorska region was not only fungal diseases but also the high level of infections, mainly with Grapevine Fanleaf Virus (GFLV) and Grapevine Leaf Roll Virus (GLRV). At the beginning, the testing was performed with test plants and indicators, but by the end of the 1980s, the tests were done with the help of the ELISA test.
1963 - establishment of the nematological laboratory; soil analysis for potato cyst nematodes (PCN). The study of free-living, mainly plantparasitic nematodes.
1986 - due to a stronger occurrence of the Plum Pox virus (PPV) in the Posavje region in 1986, we started testing parent trees, nursery plants and individual trees in stone fruit tree plantations.
1988 - the start of intensive research of economically important and extremely virulent strain of potato virus Y (PVYntn) that in 1988 almost completely prevented the production of seed potato.
1991 - with the independence of Slovenia and subsequent socio-economic changes, not only did the status of the Agricultural Institute of Slovenia change, but so did the status of the Plant Protection Department, which in the former country (ex-Yugoslavia) operated only as a regional department and after 1991 took over the function of the central professional institute for plant protection in Slovenia.