Determination of fungal diseases encountered in outdoor shrub group ornamental plants widely produced in Sakarya province and their control possibilities

This thesis aimed to identify fungal pathogens causing diseases on Aucuba japonica Thunb., Buxus sempervirens L., Euonymus japonicus Thunb., Hebe × franciscana (Eastw.) Souster 'Variegata', Nandina domestica Thunb., Photinia × fraseri Dress. 'red robin', and Viburnum lucidum Mill. grown in Sakarya, and to investigate control strategies against them. Surveys were conducted in Adapazarı, Akyazı, Arifiye, Erenler, Hendek, Sapanca, Serdivan, and Pamukova. A total of 170 fungal isolates were obtained, 73 of which were found to be pathogenic. Pathogens were identified using classical morphological methods and molecular analyses based on ITS, tef1, tub2, rpb2, LSU, and ACT gene regions. The most common pathogens were Fusarium solani (21%), Alternaria spp. (15.06%), A. alternata (9.58%), Epicoccum nigrum (6.84%), Pestalotiopsis spp. (5.46%), Colletotrichum boninense (4.10%), F. acuminatum (2.73%), and Rhizoctonia spp. (2.72%). Additionally, Botrytis cinerea, Ceratobasidium sp. AG-A (anamorph: Rhizoctonia sp.), Diplodia seriata, Neopestalotiopsis sp., Nigrospora sphaerica, Pseudonectria buxi, and Rosellinia corticium were each detected at 1.36%. Fusarium spp. were widespread in 50% of the surveyed areas, followed by Alternaria spp. (47%) and E. nigrum (20.58%). The prevalence of other pathogens remained relatively low across the surveyed locations. For the highly pathogenic Pestalotiopsis sp. 2A6 isolate from Photinia × fraseri, fungicide trials under laboratory conditions and biological control trials in a climate chamber were conducted. In the fungicide trials, tebuconazole (99.23%), difenoconazole (91.83%), and captan (81.20%) showed the highest antifungal efficacy at a concentration of 100 µg/ml. Pseudomonas fluorescens (78.61%) and Beauveria bassiana (65.79%) were the most effective biocontrol agents.