• Korean Journal of Organic Agriculture
• /
• v.24 no.4
• /
• pp.919-929
• /
• 2016

This study investigated the effect of organic materials (Bordeaux, Loess-sulfur) and the removal of apical shoot against downy mildew disease on cucumber cultivated in greenhouse. Five kinds of Bordeaux were made by adjusting mixing ratio of lime and copper sulfate in order to elucidate the optimal combination. The 4-6type Bordeaux was selected as the most effective combination for controlling cucumber downy mildew. Loess-sulfur showed inhibitory activity against cucumber downey mildew, but it was less effective than Bordeaux. It was confirmed that apical shoot cutting could reduce the incidence of cucumber downy mildew disease by 56.3%. When apical shoots of susceptible cucumber variety were cut at different leaf stages, disease incidence by early apical shoot cutting treatment was lower than that of late apical shoot cutting treatment. However in a resistant variety, 'Heukryungsamcheok', disease incidences of all cucumber apical shoot cutting treatments were lower than that of non-cutting treatment, but there was no differences between apical shoot cutting treatments due to low disease incidences. In addition, when organic materials and apical shoot cutting treatment were carried out in parallel, the combined treatments of organic materials and apical shoot cutting showed low disease incidence of cucumber downy mildew compared to untreated control. The lowest disease incidence of cucumber downy mildew was recorded in the combined treatment of 4-6type Bordeaux and apical shoot cutting. This study confirmed that apical shoot cutting can reduce the disease incidence of cucumber downy mildew and the combined treatment of apical shoot cutting and organic materials showed higher suppressive effect against cucumber downy mildew.

• The Korean Journal of Mycology
• /
• v.41 no.4
• /
• pp.261-267
• /
• 2013

In order to select antagonists for biological control of downy mildew of cucumber, 126 bacteria were isolated from cucumber plants collected from several locations in Korea. Among them, Five isolates were selected as potential biocontrol agents of cucumber downy mildew using a leaf disc bioassay method. In preventive and curative effect tests, the isolate CC110 was found to be effective to control downy mildew on cucumber showing diseased area by 0% whereas that of control was 15.0~18.0%. A bacterium isolate CC110 was identified as Bacillus amyloliquefaciens subsp. plantarum based on phylogenetic analysis using gyrB gene sequence. The culture liquid of isolate CC110 in TSB media were more effective for the control of the disease than those cultured in LB, NB, and KB media in leaf disk bioassay. when undiluted liquid, two-fold, five-fold diluted culture broth, and undiluted liquid, two-fold, five-fold diluted filtrate of isolate CC110 in TSB media were treated, diseased area of cucumber powdery mildew were 0%, 3.0%, 8.0%, 0%, 4.0% and 7.0%, respectively, whereas diseased area in the control was 21.0%. In the cucumber seedling tests, when the culture broth of isolate CC110 in TSB media was treated, diseased area were 35.0%, whereas that of control was 82.0%. When B. amyloliquefaciens CC110 was treated four times at five-day interval in the vinylhouse test, the control effect of cucumber downy mildew was higher than that treated three at seven-day interval.

• Applied Biological Chemistry
• /
• v.44 no.2
• /
• pp.109-115
• /
• 2001

The foliar uptake of dimethomoiph induced by several nonionic surfactants was measured in order to study the correlations between the uptake rate of dimethomorph and the fungicidal activity to cucumber downy mildew. Dimethomorph was not absorbed in cucumber leaf in the absence of activator surfactant. And the curative effect of dimethomoiph WP to cucumber downy mildew was very low under the concentration of 250 ${\mu}g/ml$. But dimethomorph uptake was remarkably enhanced by addition of nonionic surfactants, such as polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, and polyoxyethylene stearyl ether. And the curative effect to cucumber downy mildew was enhanced with proportion to uptake rate of dimethomorph. The protective effect to cucumber downy mildew, however, tends to decrease with the increase of foliar uptake of dimethomorph. The uptake rate of dimethomorph to cucumber leaf was proportional to the content of polyoxyethylene cetyl ether in formulation, but was decreased with dilution.

• The Plant Pathology Journal
• /
• v.22 no.3
• /
• pp.303-308
• /
• 2006

Ethaboxam is a fungicide controlling plant diseases caused by Oomycetes. Efforts were made to improve its fungicidal activity applying formulation technology. Fungicidal activity of ethaboxam against cucumber downy mildew caused by Pseudoperonospora cubensis was improved by incorporating polyoxyethylene cetyl ether (PCE) in a wettable powder formulation. It was found that the optimum combination ratio of PCE and ethaboxam was 3:1, and a tank-mix of $150{\mu}g/ml$ of ethaboxam and $450{\mu}g/ml$ of PCE would be as good as the standard 25 % WP formulation diluted to $250{\mu}g/ml$ ethaboxam without PCE in controlling cucumber downy mildew. Based on this results, a wettable powder (WP) co-formulation containing 15% of ethaboxam and 45% of PCE was developed in this study, and tested for its performance in the fields. This co-formulation showed significant improvement in persistence of fungicidal activity and curative efficacy of ethaboxam against cucumber downy mildew. The improved control efficacy was also confirmed for control of grape downy mildew caused by Plasmopara viticola and potato late blight caused by Phytophthora infestans in the field tests.

• The Plant Pathology Journal
• /
• v.35 no.4
• /
• pp.341-350
• /
• 2019

Streptomyces padanus PMS-702 strain produces a polyene macrolide antibiotic fungichromin and displays antagonistic activities against many phytopathogenic fungi. In the present study, experimental formulations were assessed to improve the production of fungichromin, the efficacy of PMS-702 on the suppression of sporangial germination, and the reduction of cucumber downy mildew caused by Pseudoperonospora cubensis. PMS-702 strain cultured in a soybean meal-glucose (SMG) medium led to low levels of fungichromin accumulation and sporangial germination suppression. Increasing medium compositions and adding plant oils (noticeably coconut oil) in SMG significantly increased fungichromin production from 68 to $1,999.6{\mu}g/ml$. Microscopic examination reveals that the resultant suspensions significantly reduced sporangial germination and caused cytoplasmic aggregation. Greenhouse trials reveal that the application of PMS-702 cultural suspensions reduced downy mildew severity considerably. The addition of Tween 80 into the synthetic medium while culturing PMS-702 further increased the suppressive efficacy of downy mildew severity, particularly when applied at 24 h before inoculation or co-applied with inoculum. Fungichromin at $50{\mu}g/ml$ induced phytotoxicity showing minor necrosis surrounded with light yellowish halos on cucumber leaves. The concentration that leads to 90% inhibition (IC90) of sporangial germination was estimated to be around $10{\mu}g/ml$. The results provide a strong possibility of using the S. padanus PMS-702 strain as a biocontrol agent to control other plant pathogens.

• Research in Plant Disease
• /
• v.27 no.4
• /
• pp.149-154
• /
• 2021

Pseudoperonospora cubensis (downy mildew) is highly virulent to various Cucurbitaceae crops, including cucumber (Cucumis sativus). We tested chlorine dioxide application in a plastic greenhouse for environment-friendly control of downy mildew disease. Spraying diluted chlorine dioxide suppressed downy mildew disease with 41.2% control efficacy. Thermal fogging with chlorine dioxide had a high control efficacy of 80.9%, confirming that this approach is useful for environment-friendly downy mildew control. Using thermal fogging to control diseases that are greatly affected by humidity, such as downy mildew, may be more effective compared with conventional dilution spray control methods.

• The Plant Pathology Journal
• /
• v.15 no.1
• /
• pp.48-52
• /
• 1999

Ethaboxam is the first proprietary fungicide developed in Korea, registered in 1998 and commercialized in 1999 by LG Chemical Ltd., Korea. It is a derivative of aminothiazole carboxamide and formulated into 25% wettable powder for practical application in fields. Ethaboxam effectively controlled cucumber downy mildew caused by Pseudoperonospora cubensis, potato late blight caused by Phytophthora infestans, and pepper Phytophthora blight caused by P. capsici, and was superior or comparable to the commercial standards, when foliarly sprayed 3∼5 times until dripping off at approximately 7-day intervals during the growing season. Ethaboxam was required at least 125 mg/liter and 250 mg/liter for effective control of cucumber downy mildew, and potato late blight and pepper Phytophthora blight, respectively. There was not phytotoxicity observed o leaves, stems or fruits of cucumber, potato and pepper from any trial.

• The Korean Journal of Pesticide Science
• /
• v.15 no.3
• /
• pp.323-328
• /
• 2011

Control efficacies of mixing of powdery mildew biofungicides with other control agents against major or fungal diseases of cucumber were investigated. Control efficacies against cucumber powdery mildew were quite different according to the kinds of biofungicides applied but those of powdery mildew biofungicides were increased by mixing application of two biofungicides. More than 80% of control efficacies on powdery and downy mildews of cucumber were obtained by mixing application of a powdery mildew biofungicide Bacillus subtilis KB-401 and a downy mildew chemical fungicide dimethomorph. Similarly, control efficacies on powdery and downy mildews of cucumber were 95% and 70% by mixing application of a powdery mildew biofungicide Bacillus subtilis KB-401 and cooking oils and yolk mixture, respectively.

• The Korean Journal of Pesticide Science
• /
• v.17 no.4
• /
• pp.428-434
• /
• 2013

An isolate of Bacillus amyloliquefaciens subsp. plantarum CC110 was selected as an effective antagonist for biological control of cucumber downy mildew caused by Pseudoperonospora cubensis. Temperature range for growth of CC110 isolate was $7.5{\sim}55.0^{\circ}C$, and its optimal temperature at $36.6^{\circ}C$. pH range for growth of CC110 isolate was 4.5~9.5, and its optimal pH at 7.0. In this study, the most effective sources of carbon and nitrogen for growth of CC110 isolate were fructose and yeast extract, respectively. The volatile of CC110 isolate was found to be effective to control downy mildew on cucumber showing no diseased area whereas that of control was 13.2% using the I plate bioassay. The culture broth and cells of isolate CC110 cultured in TSB media for 48 hours at $28^{\circ}C$ inhibited occurrence of cucumber downy mildew. The cells and culture broth were transformed into sporangia of P. cubensis by in observation under light microscope and scanning electron microscope.

• Mycobiology
• /
• v.48 no.5
• /
• pp.331-340
• /
• 2020

The family Peronosporaceae, an obligate biotrophic group of Oomycota, causes downy mildew disease on many cultivated and ornamental plants such as beet, cucumber, grape, onion, rose, spinach, and sunflower. To investigate the diversity of Peronosporaceae species in Korea, we performed morphological analysis for dried plant herbariums with downy mildew infections by two largest genera, Peronospora and Plasmopara. As a result, it was confirmed that there are five species of Peronospora and two species of Plasmopara, which have been so far unrecorded in Korea, as well as rarely known in the world; Pl. angustiterminalis (ex Xanthium strumarium), Pl. siegesbeckiae (ex Siegesbeckia glabrescens), P. chenopodii-ambrosioidis (ex Chenopodium ambrosioides), P. chenopodii-ficifolii (ex Chenopodium ficifolium), P. clinopodii (ex Clinopodium cf. vulgare), P. elsholtziae (ex Elsholtzia ciliata), and P. lathyrina (ex Lathyrus japonicus). In addition, their phylogenetic relationship was inferred by molecular sequence analysis of ITS, LSU rDNA, and cox2 mtDNA. By rediscovering the seven missing species and barcoding their DNA sequences, this study provides valuable insights into the diversity and evolutionary studies of downy mildew pathogens.