Research to Fungicide Sensitivity of Colletotrichum spp. Isolated from Apple Fruits in Cheongsong, Korea

Apple grower in the Cheongsong region, Korea has reported the increased loss of apple yield due to severe bitter rot incidence. We noticed that this indience is because the Colletotrichum population has developed resistance to commonly used fungicides. We isolated 39 Colletotrichum isolates from 13 orchards in Cheongsong, and all the isolated Colletotrichum species were identified as C. siamense or C. fructicola. These 39 strains were tested for mycelial growth and conidial germination against 12 fungicides. trifloxystrobin (30–55% in recommended concentrations) was shown lower inhibitory effect on mycelial growth. However, the inhibition of conidial germination was shown higher than mycelial growth (62–100%). Kresoxim-methyl was shown lower inhibitory effect on mycelial growth (29–55%). conidial germination inhibitory effect was shown 51% to 96%. dithianon was shown diversity response to inhibition of mycelial growth (43–100%). tebuconazole was shown high inhibitory effect on mycelial growth (84–100%) and conidial germination inhibitory effect was shown to be 64 to 100%. metconazole has been found to display with high inhibitory effect on mycelial growth (79–100%) and conidial germination (70–80%). fluazinam was shown to possess high inhibitory effect on mycelial growth (87–100%) and conidial germination (94–100%). This study provides basic information for the effective management of apple bitter rot.