Investigation of chemical and biological control posssibilities of stem canker and black scurf (Rhizoctonia solani) diseases in potatoes

In this thesis study, the effects of some fungicide (fludioxonil, flutolanil, fluxapyroxad, penflufen+prothiconazole and tolclophos-methyl thiram), plant activator (Messenger, Crop-Set, Isr-2000, Aliette) and biological preparations (T-22 Planter Box, Trianum-P, Cedriks, Serenade) on Rhizoctonia solani, which causes stem canker and black scurf in potatoes on mycelial growth have been determined and their effects on disease formation have been investigated by micro parcel trials. From fungicides tolclophos-methyl+thiram and flutolanil prevented mycelial growth by 100% from 5 ppm in vitro, while fluxapyroxad could not show complete inhibition at any concentration. In plant activators, the best effect was seen in Aliette with 31.5% inhibition at 1000 ppm, while Messenger and Crop-set were completely ineffective. Trichoderma harzianum preparations applied with dual culture, volatile antibiotic and antibotic production techniques in liquid medium, limited mycelial growth by 3.8% to 66.9%. Pseudomonas fluorescens was found to be more successful than Bacillus subtilis with an inhibition rate of 82.9% in bacterial preparations applied in dual culture. When the effects of chemicals and biological preparations on Rhizoctonia solani to cause disease are examined, tolclophos-methyl+thiram from fungicides, fosetyl-al from plant activators and Pseudomonas fluorescens from biological preparations were determined as the most successful applications and these applications prevented the occurrence of the disease at 51.6%, 59.7% and 48.6%, respectively. As a result, it has been concluded that establishing appropriate control programs with fungicides, plant activators and biological preparations such as tolclophos-methyl+thiram, Aliette and Pseudomonas fluorescens, which are found to be remarkably successful in preventing the disease, will be useful in combating this pathogen.