Influence of the disease rate scouting method on the evaluation of efficacy of fungicides for control of grape wine powdery mildew (Uncinula necator (Schwein) Burrill)

Ocenjevalci na terenu uporabljajo različne metode za ocenjevanje stopnje napada bolezni na vinski trti. Da bi ugotovili, ali metode ocenjevanja stopnje napada bolezni vplivajo na dobljene rezultate pri določanju učinkovitosti fungicidov za zatiranje oidija vinske trte, smo na Fakulteti za kmetijstvo in biosistemske vede v Mariboru izvedli praktičen in teoretičen poskus. V okviru teoretičnega poskusa smo izbrali več nizov podatkov, na katerih smo opravili statistične izračune na različne načine. Potem smo preverili, ali smo dobili primerljive rezultate pri različnih načinih izračuna stopnje napada bolezni. Praktični poskus smo izvedli v letu 2007 in sicer v vinogradu na lokaciji Nebova pri Mariboru, kjer smo ocenjevali stopnjo napada oidija na trsih sorte \u27Laški rizling\u27. Stopnjo napada bolezni smo vizualno ocenjevali po prilagojeni boniturni lestvici 0-5 (Thownsend-Heuberger metoda), katera se v praksi pogosto uporablja. Dobljene rezultate smo primerjali z rezultati pridobljenimi po neposredni metodi ocenjevanja odstotka napadene površine. Z analizo variance smo ugotavljali statistično značilne razlike med rezultati, dobljenimi z eno in drugo metodo. Ugotovili smo, da je bolj smiselno neposredno ocenjevanje (% površine) kot uporaba lestvic.Evaluators use various methods for assessing infection rates of grapevine diseases in the field. To determine whether the disease rate assessment methods have any influence in determining the effectiveness of fungicide treatments on the degree of grapevine powdery mildew control, theoretical and practical experiments were performed at the Faculty of Agriculture and Life Sciences in Maribor. Several data sets were chosen on the basis of which the degree of disease rate was calculated according to different methods. Later results of different methods were compared to determine whether they yielded comparable results. Theoretical part of the experiment served as a basis for practical part, i.e., for the field experiment carried out on \u27Laški rizling\u27 vineyard in 2007 at Nebova. The degree of disease infection was firstly assessed visually according to adjusted bonitur scale 0-5 (Thownsend-Heuberger calculation), which is commonly used in practice. Results were compared to those obtained by direct method of assessment of percent diseased area. Analysis of variance was used to determine statistically significant differences between results obtained by aforementioned methods. The results show that the direct assessment method could be more suitable than different scouting scales for the assessment of percent diseased area