• The Plant Pathology Journal
• /
• v.31 no.3
• /
• pp.305-309
• /
• 2015

After four years of cold storage, dimethachlon resistance of two laboratory-induced resistant Sclerotinia sclerotiorum isolates SCG7 and LA50 declined by 99.5% and 98.9%, respectively, and cross resistance to iprodione and procymidone also declined dramatically. Along with the decline of fungicide resistance, osmotic sensitivity to sodium chloride and glucose decreased tremendously; mycelial growth rate, sclerotia number and weight per potato dextrose agar (PDA) plate increased on average by 118.6%, 85. 5% and 64.5%, respectively; and virulence to detached leaves of oilseed rape increased by 72.7% on average. Significant negative correlations were detected between dimethachlon resistance levels and mycelial growth rate on PDA (r = -0.980, P = 0.021), and between resistance levels and lesion diameters on detached leaves of oilseed rape plants (r = -0.997, P = 0.002). These results have profound implications for assessing the potential risk for resistance development to dicarboximide fungicides in S. sclerotiorum.

• Research in Plant Disease
• /
• v.26 no.2
• /
• pp.61-71
• /
• 2020

With 32 fungicides, it was examined the inhibitory effects on the mycelial growth of Alternaria dauci KACC42997 causing Alternaria leaf blight of carrot. Showing the results of the agar dilution method, the fungicides belonging to C2, C5, G1, E2, and E3 group were excellent in inhibiting mycelial growth. Protective fungicides belonging to M group, except for iminoctadine tris-albesilate, and pyraclostrobin belonging to C3 group were effective in inhibiting spore germination of pathogens. The fungicides included into C2 group inhibiting succinate dehydrogenase activity and the G1 group inhibiting demethylase activity showed the excellent inhibitory effect on mycelial growth but the inhibitory effect of spore germination was very low. However, fluazinam belonging to C5 group was excellent in inhibiting spore germination as well as mycelial growth. Especially, when 100 ㎍/ml of fluxapyroxad belonging to the C2 group was treated, 47.1% of spore formation was inhibited on the medium. In comparison of the resistance factors of 3 fungicide groups, as G, C, and E group, in populations of A. dauci isolates collected from Gumi, Pyeongchang, and Jeju, resistance factor in the population of Jeju was the lowest. However, two isolates resistant to fludioxonil belonging to E2 group were found in the isolate group of Pyeongchang, and both showed cross-resistance to iprodione and procymidone.

• The Plant Pathology Journal
• /
• v.19 no.1
• /
• pp.46-50
• /
• 2003

To evaluate the sensitivity of Monilinia fructicola to dicarboximides used in controlling brown rot of peach, the fungus was isolated from commercial peach orchards in Chochiwon (CH), Chongdo (CD), Gyeongsan (GY), and Youngduk (YO) in Korea. The population shift of dicarboximide-resistant isolates of M. fructicola was investigated for 3 years starting 1998. The frequency of procymidone-resistant isolates (PRI) was higher in CD and GY than in CH and YO. The frequency of PRI was higher in the mid season (July-August) than in the rest of the year. Cross-resistance rate of PRI to iprodione was over 87.8% during the investigation, and double-resistance to both procymidone and carbendazim was less than 10%. However, the rate of cross-resistant isolates to vinclozolin was low. In the orchards in GY and CH without any fungicide spray, the PRI population was persistent and did not vary for 3 years. The results suggest that dicarboximide resistance of M. fructicola could be a problem in controlling brown rot and blossom blight on peach trees because it may take a long time to recover the population with sensitive isolates even in the absence of these fungicides.

• Journal of Mushroom
• /
• v.9 no.4
• /
• pp.198-201
• /
• 2011

Cobweb disease symptoms were observed in a mushroom farm in Buye, Korea during a disease survey in 2008-2011. Five isolates of Cladobotryum sp. were obtained from the infected caps and stipes. These isolates of Cladobotryum sp. were identified as C. mycophilum based on their morphological, cultural characteristics and analysis of the ITS sequences. Early symptoms were noticed as round, fleshy, yellowish brown lesions on mushroom caps. Late symptoms progressed when the parasitic fungus formed white cobweb circular colonies on dead or damaged pinheads, spread on the surface of the casing, and covered entirely fruiting bodies. Optimal temperature and pH for mycelial growth on MEA is $23^{\circ}C$ and 6.0. Microscopically the spores of the fungus are large and most 2~3 celled produced on vertically branched conidiophores. Mushroom caps turned dark brown and shrunk due to soft rot. Testing of sensitivity to selected fungicides showed that isolate was highly resistance to Mancozeb and Thiophanate-methyl, moderately sensitivity to Iprodione, and highly sensitivity to Benomyl, Prochloraz-Mn and Carbendazim.

• The Plant Pathology Journal
• /
• v.32 no.6
• /
• pp.570-574
• /
• 2016

Botrytis cinerea is a necrotrophic pathogen causing a major problem in the export and post-harvest of strawberries. Inappropriate use of fungicides leads to resistance among fungal pathogens. Therefore, it is necessary to evaluate the sensitivity of B. cinerea to various classes of fungicide and to determine the effectiveness of different concentrations of commonly used fungicides. We thus evaluated the effectiveness of six classes of fungicide in inhibiting the growth and development of this pathogen, namely, fludioxonil, iprodione, pyrimethanil, tebuconazole, fenpyrazamine, and boscalid. Fludioxonil was the most effective ($EC_{50}$ < $0.1{\mu}g/ml$), and pyrimethanil was the least effective ($EC_{50}=50{\mu}g/ml$), at inhibiting the mycelial growth of B. cinerea. Fenpyrazamine and pyrimethanil showed relatively low effectiveness in inhibiting the germination and conidial production of B. cinerea. Our results are useful for the management of B. cinerea and as a basis for monitoring the sensitivity of B. cinerea strains to fungicides.

• Applied Biological Chemistry
• /
• v.42 no.4
• /
• pp.356-360
• /
• 1999

Growth-inhibitory effects of citrus oils and agricultural fungicides, which were on the market, on several molds isolated from putrefied citrus fruits were investigated. When fungicidal activities of 11 kinds of synthetic agrochemicals against 6 species of molds, Alternaria alternata, Rhizopus sp., Botrytis cinerea, Monilia candida, Penicillium italicum and Penicillium digitatum, were investigated, agrochemicals containing mancozeb or fluazinam as an effective component had the broadest fungicidal spectrum. Agrochemicals containing iprodione, benomyl, azoxystrobin or thiophanate were less effective on the molds and those containing conazole derivative were intermediately effective. Resistance of the molds to the agrochemicals were species- and agrochemical-dependent. Among those molds tested, Penicillium italicum and Alternaria alternata showed relatively higher level of survival in the presence of synthetic fungicides. On the other hand, when the molds were exposed to citrus oils by direct contact, no cell could survive regardless of the species. The fungicidal activity of citrus oils was also confirmed by paper disk method and microscopic observation. These results suggested that citrus oils had broad killing activity against molds. Therefore, it would be necessary to design method for the application of citrus oils in order to improve post-harvest storage of citrus fruits.

• The Korean Journal of Pesticide Science
• /
• v.9 no.4
• /
• pp.429-436
• /
• 2005

As Sclerotinia sclerotiorum causing cucumber sclerotinia rot was the fastest in the mycelial growth at $25^{\circ}C$, its pathogenicity was strong at the same temperature among several temperatures. All the isolates of Sclerotinia sclerotiorum showed a strong pathogenicity against cucumber fruits, which was confirmed by a disk assay and a wound assay. A wound assay was superior to a disk assay to develop the assay system for assessing the fungicidal activity of several fungicides against Sclerotinia sclerotiorum. In a disk assay, it was very difficult to assess the fungicidal activity, because the pathogenicity of isolates used in the experiment was very strong. At 500 and $3.0{\mu}g/mL$, the activity of dichloflouanid and the mixture of carbendazim and diethofencarb against cucumber sclerotinia rot was 14.3 and 42.3%, respectively, by using a disk assay. However, at same concentration two fungicides showed the high controlling activity as 100 and 92.5%, through a wound assay in a laboratory. Also, the activity of two fungicides was good against cucumber sclerotinia rot in the greenhouse where cucumber plants were cultivated in the field, showing the control value as 91.1 and 82.9% at 100 and $825{\mu}g/mL$, respectively. All the isolates of Sclerotinia sclerotiorum from cucumber fruits sampled in the polyvinyl house were subjected to monitoring for the resistance to 7 fungicides. The $EC_{50}$ value of 7 fungicides was as follows: fenhexamid; $0.13{\mu}g/mL$, procymidon and iprodione; 0.18 and $0.24{\mu}g/mL$, carbendazim and the mixture of carbendazim and diethofencarb; 0.13과 $0.05{\mu}g/mL$, iminoctadine and dichlofluanid; 1.94 and $8.95{\mu}g/mL$. Ultimately it was not found that resistant isolates of Sclerotinia sclerotiorum were appeared in the field.