• Horticultural Science & Technology
• /
• v.32 no.5
• /
• pp.673-683
• /
• 2014

This study was conducted to establish an efficient screening method to identify cucurbits resistant to powdery mildew. Powdery mildew fungus was obtained from a single lesion of infected cucumber leaf in 2010 at Daejeon. The fungus was identified as Podosphaera xanthii race 1 based on morphological characteristics and resistance responses of four melon differentials. Development of powdery mildew caused by the fungal isolate on 34 commercial cultivars of cucumber was investigated at three plant growth stages in a greenhouse. The degree of resistance of cotyledons of each cultivar to the fungus was not correlated with that of whole plant, but powdery mildew occurrence in the first true leaf was highly correlated with resistance at the level of the whole plant. Based on these results, the first true leaf of cucurbit cultivars can be used for screening of resistance to powdery mildew. In addition, variation of resistance of commercial 12 cucumber and 26 melon cultivars to the powdery mildew fungus due to different growing seasons was tested. In the case of cucumber, the resistance response in some cultivars was influenced by growing season. The resistant cultivars showed higher resistance in the warm season than in the cool season. By contrast, the resistant melon cultivars demonstrated strong resistance in all the tested growing seasons. Interestingly, the tested powdery mildew pathogen, a member of P. xanthii race 1, was not pathogenic on seven cultivars of watermelon (Citrullus lanatus). To follow up on this, diverse race 1 isolates of P. xanthii should be collected and tested.

• The Plant Pathology Journal
• /
• v.18 no.2
• /
• pp.102-105
• /
• 2002

A strain of Acremonium strictum, the mycoparasite of Botrytis cinerea, showed strong antifungal activities both in vitro and in vivo against several phytopathogenic fungi. An antifungal substance was purified from the liquid cultures of A. strictum and identified as verlamelin by instrumental analyses. Verlamelin exhibited in vitro antifungal activity against some phytopathogenic fungi such as Magnaporthe grisea, Bipolaris maydis, and Botrytis cinerea, while it was net active against all the bacteria tested. In viva, verlamelin exhibited strong protective and curative activities, particularly against barley powdery mildew. At 100 μg/ml, it inhibited the development of barley powdery mildew with control values of more than 90% in 7-day protective and 2-day curative applications. This is the first report on the production of verlamelin by Acremonium species.

• Journal of Microbiology and Biotechnology
• /
• v.16 no.3
• /
• pp.465-468
• /
• 2006

Even though many pesticides are known for barley powdery mildew and wheat leaf rust, alternative controls are necessary, because of consumer rejection of chemical pesticides and the appearance of fungi resistant to fungicides. To discover biopesticides, many broths of microorganisms were screened. Of those, a culture broth of Burkholderia ambifaria showed an excellent antifungal activity against both Erysiphe graminis and Puccinia recondita, which cause barley powdery mildew and wheat leaf rust, respectively.

• The Plant Pathology Journal
• /
• v.24 no.1
• /
• pp.63-66
• /
• 2008

The fermentation broth (FB) of Streptomyces griseofuscus 200401 isolated from non-farming soil showed antagonistic activity against powdery mildew fungus both in melon leaf/seedling assay and in field trials. The FB of S. griseofuscus 200401 was tested at different concentrations. In primary test, the control value of 2-fold diluted FB of S. griseofuscus 200401, compared to control, reached to 82.8%. The protective activity recorded 80.5% in 2-fold dilution of FB. The effect was reduced to 28.9% in high dilution (100-fold) treatment. The curative effect was relatively lower than protective activity. In field test, the antifungal activities of S. griseofuscus 200401 remained low in blocks sprayed with 100-fold diluted FB and the control values were 15.2 and 15.9% in 2005 and 2006, respectively. However, the activities were as high as 65% and 67.3% in the blocks treated with 2-fold dilution of FB during the same period.

• The Plant Pathology Journal
• /
• v.33 no.4
• /
• pp.434-439
• /
• 2017

Incidence rates of diseases in kiwiberry orchards were investigated monthly from late June to late September in Gwangyang and Boseong in 2015 and 2016. The impact of postharvest fruit rot was investigated during ripening after harvest. Bacterial canker was only observed on one single tree in 2015, but black rot, powdery mildew, leaf spot and blight, and postharvest fruit rot diseases were problematic throughout the study period in both 2015 and 2016. Incidence rates of the diseases varied with kiwiberry cultivar, region and sampling time. Incidence rates of powdery mildew, leaf spot and blight diseases increased significantly during the late growing stages near fruit harvest, while black rot peaked in late August. Incidence rate of postharvest fruit rot on fruit without fruit stalks was less than half of fruit with fruit stalks, regardless of kiwiberry cultivars. Among the four cultivars, Mansu was relatively resistant to black rot and postharvest fruit rot diseases. In our knowledge, this is the first report of various potential pathogens of kiwiberry in Korea.

• Journal of Life Science
• /
• v.18 no.7
• /
• pp.974-979
• /
• 2008

The powdery mildew, a fungal plant disease found in varieties of plant cultures, is occurred by attack with Fusarium sp., Sphaerotheca sp., Leveilluna sp., and Eryshipe sp.. In this study we investigated the control of Fusarium graminearum, a barley powdery mildew fungus, by natural plant extracts. Among the 900 plant extracts tested, Zanthoxylum schinifolium, Ligusticum acutilobum, Bidens frondosa L., Dictamnus dasycarpus, Evodia officinalis, Disporum sessile, Scopolia japonica Max., Styrax japonica S. et Z., Dictamnus dasycarpus Turcz., Sinomenium acutum Rehder et Wils., Eugenia aromaticum, Rubus parvifolius L., Reynoutria elliptica, Coptis chinensis, Paeonia lactiflora Pall., Rheum undalatum, Paeonia suffruticosa, Oenothera odorata Jacq., Euphorbia pekinensis Rupr., and Nepeta cataria were selected based on spore germination inhibition assay. Further mycelial growth inhibition assay with economical and safety considerations led us to finally select Z. schinifolium (sancho) for control of F. graminearum. To produce antifungal sancho extract, methanol was suitable for extraction and subsequent fractionations of the extract showed that the water residue mainly had antifungal activity. The sancho extract and its fractions showed minor antibacterial activity against different pathogenic or food spoilage bacteria, but they did not show any harmful effects against young tomato plant by treatment of $1,000\;{\mu}g/ml$ in green chamber test. These results suggested that the extract of sancho has high potentials on control of a powdery mildew fungus, F. graminearum.

• The Korean Journal of Pesticide Science
• /
• v.18 no.4
• /
• pp.376-382
• /
• 2014

The soluble loess-sulfur mixture allowed standing to remove insoluble component materials for five weeks after manufacturing. We decreased the pH level of soluble loess-sulfur mixture at pH 1.0 modified with decreasing 25% sodium hydroxide than original content. The pH ranges of soluble loess-sulfur mixture solutions were adjusted to pH 5.0-pH 11.0 (pH 1 unit) with brown rice vinegar (pH 2.8). The pH of original loess-sulfur mixture was about pH 13 and damaged the foliar parts and young leaves of tomato after twice application. These stock solutions can be diluted 500:1 with tap water to make a 0.05% working solution and were sprayed two times with 7 days interval to the leaf and stem of tomato, which were spontaneously infected with E. cichoracearum. Control efficacy of powdery mildew ranged from 85% to 90% at 7 days after first application. After second application, each loess-sulfur mixture solutions adjusted pH level significantly suppressed the powdery mildew disease in tomato. Consequently, loess-sulfur complex adjusted pH level with brown rice vinegar was suggested to be low in acute toxicity at all different pH values and suggested to use an agent for control of tomato powdery mildew in organic farming.

• The Korean Journal of Pesticide Science
• /
• v.20 no.2
• /
• pp.145-151
• /
• 2016

This study was carried out to develop the economic thresholds for powdery mildew on eggplant. To investigate the relationship between powdery mildew incidence degree and yield, experimental plots with ten treatments as the initial disease degree were established. Disease severity exhibited negative and significant correlation with fruit weight and number of fruit. There existed close correlation between rate of diseased leaf area and yields in the greenhouse (control with fungicide Y = -36.5X+2938.5 $R^2=0.91$ $r=-0.913^*$, no fungicide: Y = -29.57X+2574.4 $R^2=0.73$ $r=-0.858^*$). There existed close correlation between rate of diseased leaf area and yield loss in the greenhouse (Y = 1.27X-2.4 $R^2=0.88$ $r=0.91^*$). The economic thresholds for powdery mildew on eggplant was below 14.7% rate of diseased leaf area per plant in the greenhouse.

• Research in Plant Disease
• /
• v.14 no.2
• /
• pp.95-101
• /
• 2008

Fungicide resistance of cucumber powdery mildew was screened among the pathogens isolated from diseased plants in main cucumber productuion areas in Gyeonggi Province. Each fungicide from different activity group for the control of powdery mildew were sprayed on cucumber leaves according to application concentration. Each conidia mixed with sterilized water isolated of pathogens were transferred on the cucumber leaf disks treated with each fungicide. At 7 to 9 days after inoculation of pathogen, disease severity was recorded under the microscope. Most of pathogen isolates showed moderate resistance to difenoconazole belonged to DMI group fungicide while some isolates from Osan were resistant even $300{\mu}g/ml$. Isolates from Pyeongtaek, Osan and Yongin area also showed moderate resistance to fenarimol while one isolate showed resistant to fenarimol even $300{\mu}g/ml$. Most of isolates from Pyeongtaek, Osan and Yongin showed highly resistant to azoxystrobin belonged to strobilurin group fungicide. Standard sensitive isolates the minimum inhibition concentration(MIC) value for azoxystrobin showed $200{\mu}g/ml$ while resistance isolates showed above $2000{\mu}g/ml$. Resistant isloates also showed cross resistance among strobilurin group fungicides and low control efficacy in the field test. These results suggest that treatment of strobilurin fungicides should be reduced for the control of powdery mildew.

• Research in Plant Disease
• /
• v.13 no.1
• /
• pp.40-44
• /
• 2007

Powdery mildew of pepper is one of the most devastating diseases which is occurring all the year under greenhouse condition. In this study, control efficacy against powdery mildew was evaluated by mixed culture solutions of two chitinolytic bacteria, Lysobacter enzymogenenes strain C-3 and Chrornobacterium sp. strain C-61, cultivated in the chitin-supplemented medium. In all experiments, white powder on the reverse side of pepper leaves perfectly disappeared 3 days after application of mixed culture solutions. However, periods required for formation of new white powder on the same sites after application (control-lasting period) were largely differed according to environmental conditions. In particular, the control-lasting period was much longer when sprayed on 6 PM than 9 AM and especially, on rainy days than sunny days. This indicates that control efficacy of culture solution may be largely affected by environmental conditions after application. The undiluted culture solution resulted in a perfect control with control value more than 95% by application of 5-day-intervals under severely diseased field and 7-day-intervals under disease-started field. A ten-fold diluted product also showed control value more than 81% by application of the same method. These results suggest that this culture solution can be practically used to control powdery mildew disease in pepper plants.