• The Korean Journal of Mycology
• /
• v.30 no.2
• /
• pp.157-165
• /
• 2002

Of 125 isolates collected from 35 golf courses, sensitivity of 44 isolates of Pythium species to metalaxyl was determined on corn meal agar with various concentrations of metalaxyl (0.1, 1.0, 10.0, 50.0, 100.0, and $250.0{\mu}g\;a.\;i/ml$). The isolates were able to be categorized into the sensitive and resistant groups based on hyphal growth measured in terms of colony diameters on the medium with $1.0\;and\;10.0{\mu}g\;a.\;i./ml$. When compared with hyphal growth on the medium without metalaxyl, hyphal growth of the sensitive group which included 31 isolates was inhibited by $66{\sim}98%$ on the medium with $1.0{\mu}g\;a.\;i./ml$, whereas that of the resistant group which included 13 isolates grew well and the hyphal growth was inhibited only by $6{\sim}26%$. When $10.0{\mu}g\;a.\;i./ml$ of metalaxyl was included in the medium, hyphal growth of the sensitive and resistant groups was inhibited by $82{\sim}99%\;and\;27{\sim}47%$, respectively. Occurrence of metalaxyl-resistant isolates of Pythium spp. not only from turfgrasses on golf courses but also from other crops was observed for the first time in Korea. Metalaxyl-resistant isolates occurred most frequently in P. graminicola. Control effects of metalaxyl were determined by applying metalaxyl after and before inoculation of 4 and 3 isolates of sensitive and resistant isolates of P. graminicola, respectively, to creeping bentgrass in pots. The minimum concentration of metalaxyl to control metalaxyl-sensitive isolates was $6.25{\mu}g\;a.\;i./ml$, whereas the disease caused by the metalaxyl-resistant isolates could not be controlled with $12.50{\mu}g\;a.\;i./ml$ of metalaxyl. The disease was controlled more effectively by an application of metalaxyl prior to inoculation than after occurrence of the disease.

• The Korean Journal of Pesticide Science
• /
• v.13 no.4
• /
• pp.283-289
• /
• 2009

Isolation frequency of resistant isolates of Phytophthora capsici to metalaxyl was reported to be 38.9% through the resistance monitoring for metalaxyl in P. capsici causing pepper Phytophthora blight. Metalaxyl was very effective to mycelium growth, while not to zoosporangium germination and zoospore release. $EC_{50}$ values of metalaxyl in the inhibition of mycelium growth were 0.204, 0.151, 0.379, and $0.215\;{\mu}g\;mL^{-1}$ against each isolate sensitive to the fungicide as P. capsici 06-119, 06-143, P08-7, and P08-31, respectively, whilst those were 5.242, 5.724, 6.621, and $5.377\;{\mu}g\;mL^{-1}$ in P. capsici 06-125, 06-155, P08-50, and P08-60. For the field fitness, several factors, which were mycelium growth, zoosporangium germination, zoospore release, virulence to pepper plants, and the zoosporangium and the oospore production, were investigated with 4 sensitive isolates and 4 resistant isolates. Between 2 groups differentiated by the sensitivity of metalaxyl, there was no significance in mycelium growth, zoosporangium germination, zoospore release, and virulence to pepper plants. However, the zoosporangium and the oospore production in each resistant isolate, which were related to survival of P. capsici in fields, were superior to those of sensitive isolates. Based on results of this study, it was suggested that the increase of the percentage of resistant isolates to metalaxyl resulted from the high capacities of the zoosporangium and the oospore production.

• Proceedings of the Korean Society of Plant Pathology Conference
• /
• 2000.10a
• /
• pp.23.1-23
• /
• 2000

• The Korean Journal of Pesticide Science
• /
• v.14 no.4
• /
• pp.456-462
• /
• 2010

Baseline sensitivity to benthiavalicarb, iprovalicarb and dimethomorph included into carboxylic acid amide (CAA) group was evaluated in 180 isolates of Phytophthora capsici over 4 years from 2005 to 2008. $EC_{50}$ (effective concentration inhibiting mycelial growth by 50%) value of benthiavalicarb ranged from $0.015{\mu}g\;mL^{-1}$ to $0.049{\mu}g\;mL^{-1}$ with a mean of $0.033{\mu}g\;mL^{-1}$. The mean values of $EC_{50}$ of iprovalicarb and dimethomorph were 0.411 (0.197 - 0.556) ${\mu}g\;mL^{-1}$ and 0.271 (0.101 - 0.798) ${\mu}g\;mL^{-1}$, respectively. Although there was no increasing tendency in $EC_{50}$of benthiavalicarb and iprovalicarb during 4 years, $EC_{50}$ of dimethomorph was increased gradually by laps of time. There was no cross-resistance between each fungicide used in this study and metalaxyl. Among fungicides included into CAA group, there was a positive correlation between benthiavalicarb and iprovalicarb, and between dimethomorp and mandipropamid.

• The Plant Pathology Journal
• /
• v.17 no.6
• /
• pp.382.5-383
• /
• 2001

• The Korean Journal of Pesticide Science
• /
• v.3 no.1
• /
• pp.29-36
• /
• 1999

A series of N-phenyl-O-phenylthionocarbamate derivatives were synthesized and determinated fungicidal activities in vitro against gray mold (Botrytis cinerea) and capsicum phytophthora blight (Phytophthora capsici) which showed resistance and sensitivity to benomyl and metalaxyl as systemic fungicides, respectively. The structure-activity relationship (SAR) was investigated by Free-Wilson analysis method and Hansch method. From the basis on the findings, the N-phenyl(X) groups had more contributions than O-phenyl(Y) groups did and ortho-substituents on the N-phenyl group showed high fungicidal activities. Especially, 4-cyano substituent, 2 as X-group showed 50% inhibition($pI_{50}=5.50$) of hyphae growth at 0.8ppm against resistance P. capsici (RPC) And hydroxyl substituents, 12 and 23 displayed the highest fungicidal activity against resistant B. cinerea (RBC), sensitive B. cinerea (SBC), and sensitive P. capsici (SPC). Antifungal activities of SPC were dependent upon molar refractivity (MR) constant and those of others relied on hydrophobic parameters (${\sigma}$ and logP). For increasing fungicidal activity against RPC and SBC, the optimum values of the sigma (${\sigma}$) and field(F) constants as electron withdrawing groups were 0.32 and 0.18, respectively.