• Asian Journal of Turfgrass Science
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• v.13 no.4
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• pp.223-234
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• 1999

Antibiotic activity of selected biocontrol agent Trichoderma harzianum ABGS-95 showed 59% to P. graminicola, 65% to P. aphanidermatum and 57% to Rhizoctonia solani compare to non-treated control. ABGC-95 showed resistant to major agrochemicals such as metalaxyl+mancozeb, etridiazole, propamocarb, toclofos methly, terbuconazole, pencycuron and flutolanil. The biocontrol agent T. harzianum ABGC-95 grew vigorously in low nutrient media and water agar. And sand mixture with wheat bran or mowing debris of zoysia grass also provided good growth of the organism. Application of sand mixture of Trichoderma spp. into aeration cores in golf showed most effective biocontrol of pythium blight. Top dressing application of T. harzianum ABGC-95 reached 83% control efficient while spray application of same biocontrol agent showed only 69% control. The biocontrol agent ABGC-95 successfully suppressed the population density of Pythium spp. in soil. The population density of total Pythium spp. in ABGC-95 treated soil was sustained almost same population at beginning(early May) up to end of August, while the population in untreated control plot was increased 5 times that of beginning and even 10 times in pathogen accumulated soil.

• The Plant Pathology Journal
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• v.39 no.4
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• pp.351-360
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• 2023

Citrus melanose, caused by Diaporthe citri, has been one of the serious diseases, and chemical fungicides were used for protection in many citrus orchards of Jeju Island. Establishing a disinfectant resistance management system and reducing pesticide usage would be important for contributing to safe agricultural production. In this study, monitoring of chemical resistance was performed with 40 representative D. citri isolates from many citrus orchards in Jeju Island. Four different fungicides, kresoxim-methyl, benomyl, fluazinam, and prochloraz manganese, with seven different concentrations were tested in vitro by growing the mycelium of the fungal isolates on the artificial medium potato dextrose agar. Among the 40 fungal isolates, 12 isolates were investigated as resistant to kresoxim-methyl which could not inhibit the mycelium growth to more than 50%. Especially isolate NEL21-2 was also resistant against benomyl, whose hyphae grew well even on the highest chemical concentration. However, any chemical resistance of fungal isolates was found against neither fluazinam nor prochloraz manganese. On the other hand, in vivo bio-testing of some resistant isolates was performed against both kresoxim-methyl and benomyl on young citrus leaves. Typical melanose symptoms developed on the citrus leaves pre-treated with both agrochemicals after inoculation with the resistant isolates. However, no or less symptoms were observed when the susceptible isolates were inoculated. Based on these results, it was suggested that some resistant isolates of D. citri occurred against both systemic fungicides, which may be valuable to build a strategy for protecting citrus disease.

• The Plant Pathology Journal
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• v.35 no.3
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• pp.219-233
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• 2019

Soybean cultivars susceptible to Phytophthora root and stem rot are vulnerable to seed rot and damping-off of seedlings and young plants following an infection by Phytophthora sojae. In this study, the disease responses of Japanese soybean cultivars including currently grown main cultivars during the early growth stages were investigated following infections by multiple P. sojae isolates from Japanese fields. The extent of the resistance to 17 P. sojae isolates after inoculations at 14, 21, and 28 days after seeding varied significantly among 18 Japanese and two US soybean cultivars. Moreover, the disease responses of each cultivar differed significantly depending on the P. sojae isolate and the plant age at inoculation. Additionally, the treatment of 'Nattosyo-ryu' seeds with three fungicidal agrochemicals provided significant protection from P. sojae when plants were inoculated at 14-28 days after seeding. These results indicate that none of the Japanese soybean cultivars are completely resistant to all tested P. sojae isolates during the first month after sowing. However, the severity of the disease was limited when plants were inoculated during the later growth stages. Furthermore, the protective effects of the tested agrochemicals were maintained for at least 28 days after the seed treatment. Japanese soybean cultivars susceptible to Phytophthora root and stem rot that are grown under environmental conditions favorable for P. sojae infections require the implementation of certain practices, such as seed treatments with appropriate agrochemicals, to ensure they are protected from P. sojae during the early part of the soybean growing season.

• Research in Plant Disease
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• v.12 no.3
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• pp.260-266
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• 2006

Pythium blight caused by Pythium spp. is one of major diseases in putting green of golf course. In this study, microorganisms which are anatgonistic to Pythium aphanidermatum, a pathogen of pythium blight, were selected primary through in vitro tests, dual culture method and triple layer agar diffusion method. In vivo test against pythium blight were conducted to select the best candidate biocontrol microorganism by pot experiment in a plastic house. Bacillus subtilis GB-0365 was finally selected as a biocontrol agent against pythium blight. Relative Performance Indies(RPI) was used as a criterion of selecting potential biocontrol agent. B. subtilis GB-0365 showed resistance to major synthetic agrochemicals used in golf course. Alternative application of synthetic agrochemicals and B. subtilis GB-0365 was most effective to successfully contol pythium blight. B. subtilis GB-0365 suppressed the development of pythium bight of bentgrass by 56.4% as compared to non-treated control and its disease control efficacy was 60.9% of a synthetic fungicide Oxapro(WP) efficacy. B. subtilis GB-0365 has a potential to be a biocontrol agent for control of pythium blight.

• Korean journal of applied entomology
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• v.25 no.1 s.66
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• pp.27-32
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• 1986

To establish a method for measuring varietal resistance against rice stem maggot in field and pot, 20 varieties were used in $1981{\sim}1983$. The degree of injured stems by the 1st generation larvae was significantly correlated with that of injured panicles by the 2nd ($r=0.864^{**}$). There was no ovipositional preference in rice stem maggot. The larval mortality after artificial infestation varied widly from 5.6 to 100% in varieties and that of the resistant varieties was high after boring. There was a negative correlation between number of injured leaves and larval mortality after artificial infestation ($'81:r=-0.833^{**},\;'82:r=-0.918^{**}$). It is considered that larval mortality mainly caused by antibiosis and larval mortality 20 days after infestation on rice seedlings is ideal for evaluating the varietal resistance to rice stem maggot. Resistant varieties are Nagdongbyeo, Jinjubyeo and Chucheongbyeo susceptible varieties, Keumgangbyeo, Milyang 23, Baigyangbyeo and Milyang 30.