• The Korean Journal of Pesticide Science
• /
• v.14 no.4
• /
• pp.326-331
• /
• 2010

Bacillus subtilis B29, B. subtilis M10 and Streptomyces sp. CC19 obtained from phyllosphere of cucumber plants were selected for biological control of fungal air-borne diseases. For the downy mildew, diseased area of B. subtilis B29, B. subtilis M10 and Streptomyces sp. CC19 showed 0.5%, 20.2% and 42.0%, but that of control was 82.0% respectively, in cucumber seedling test. Incidence of powdery mildew by once application of B. subtilis B29, B. subtilis M10 and Streptomyces sp. CC19 was 2.8%, 3.6% and 12.3%, respectively, whereas that of control was 65.6%. On the gray mold, diseased area of B. subtilis B29, B. subtilis M10 and Streptomyces sp. CC19 was 8.0%, 30.8% and 5.2%, respectively, compared to 81.2% for the control. Therefore, B. subtilis B29 could be a prospective antagonist for biological control of powdery mildew, downy mildew and gray mold of cucumber plant.

• Applied Biological Chemistry
• /
• v.48 no.1
• /
• pp.34-39
• /
• 2005

There are various crop diseases in green houses that are caused by the cultural environments, especially high temperature and moisture. To solve the forementioned problems, farmers are overusing agricultural chemicals, causing other damages by the chemical residue. In this study, antagonistic bacteria as biological control agents were isolated to produce the environmentally-friendly crops for use in green houses. Eighteen species of antagonistic bacteria were totally isolated from the soil and plants in the Perilla fields, and AK-17 showed the highest activity among the isolates. According to the results of anti-fungal spectrum against several pathogens by AK-17, the antagonism effect of the isolates was remarkable against grey mold rot by Botrytis cinerea, sclerotinia rot by Sclerotnia sclerotiorum, and stem rot by Rhizoctonia solini. To evaluate the biological control effects of the isolates against the major diseases of Perilla, studies were carried out to evaluate the preventive and the curative effects of the diseases throughout the pot experiments. According to the forementioned experiments, the preventive and the curative effects by the isolates against sclerotinia rot were respectively showed as 55% and 92%. For the grey mold rot, those were 40% and 78%, respectively. As to the evaluation of the growth-promoting effect by AK-17, the length and the biomass of the tested plants were increased to 120% and to 164%, respectively. For the leaf numbers and area were respectively increased to 120% and 220%. Furthermore, AK-17 was identified as Burkhoderia sp. according to the results of physiological properties and genetic methods.

• The Korean Journal of Pesticide Science
• /
• v.3 no.3
• /
• pp.37-44
• /
• 1999

Two sulphamide (dichlofluanid and tolylfluanid) and three dicarboximide fungicides (iprodione, vinclozolin, procymidone) were used to investigate the correlation between in vitro antifungal activities and in vivo disease controlling activities against Botrytis cinerea, a causal agent of tomato gray mold and to develop efficient in vitro assays. They controlled effectively the development of tomato gray mold disease in vivo and their controlling activities were similar one another. However, several in vitro assays revealed that their in vitro antifungal activities were quite different between sulphamide and dicarboximide fungicides; the formers showed stronger inhibition activities for spore germination than the latters, whereas the formers inhibited mycelial growth less severely than the latters. The results indicate that the fungicides having different modes of action can show different in vitro antifungal activities according to in vitro assays, even if they have similar in vivo disease controlling activities. On the other hand, two rapid and efficient in vitro assays named Microtiter plate methods I (MPM I) and II (MPM II) were developed for the evaluation of fungicides for inhibitory activities against spore germination and mycelial growth of B. cinerea, respectively. The antifungal activities of five fungicides of two chemical groups in MPM I and II were correlated with the inhibitory activities against spore germination and mycelial growth using solid media, respectively.

• The Korean Journal of Pesticide Science
• /
• v.20 no.2
• /
• pp.152-158
• /
• 2016

The cause of death was investigated with several dead cabbage moth larvae in breeding box. Bacterial strains were isolated and selected from the dead larvae by bioassay. One of them was identified as Serratia marcescens used by morphological characteristics and gene sequencing. S. marcescens were cultured by Luria Bertani (LB) media broth for bioassay. When 100-fold dilution of culture broth to third larvae of diamondback moth, Plutella xylostella, it was showed a 100% mortality at 2 days after treatment, and only 10-fold dilution of supernatant liquid was showed 86.6% mortality. When the culture broth of S. marcescens was applied to the larvae of beet armyworm, Spodoptera exigua, contact and feeding toxicity were 20 and 8% of mortality, respectively. Otherwise, when the culture broth of S. marcescens was applied to 5 major plant pathogens, antibacterial activities against Fusarium oxysporum, Rhizoctonia solani, Colletotrichum gloeosporioides, Phytophthora capsici and Sclerotinias clerotiorum were 4.7, 11.3, 20, 15.7 and 42.6%, respectively. Also, degradation ability of S. marcescens against protein and chitin were examined.

• Research in Plant Disease
• /
• v.26 no.1
• /
• pp.8-18
• /
• 2020

Red pepper, one of the major economic crops in Korea, is being affected by anthracnose disease caused by Colletotrichum acutatum. To control this disease, an antagonistic bacterial strain, Bacillus subtilis YGB36 identified by 16S rDNA sequencing, physiological and biochemical analyses is used as a biological control agent. In vitro screening revealed that the strain YGB36 possess strong antifungal activity against the pathogen Cylindrocarpon destructans. The strain exhibited cellulase, protease, amylase, siderophore production and phosphate solubility. In vitro conidial germination of C. acutatum was most drastically inhibited by YGB36 cell suspensions (10⁶ cfu/ml) or culture filtrate. Development of anthracnose symptoms was reduced on detached immature green pepper fruits by treatment with cell suspensions, and its control value was recorded as 65.7%. The YGB36 bacterial suspension treatment enhanced the germination rate of red pepper seeds and promoted root development and growth under greenhouse conditions. The in vitro screening of fungicide and insecticide sensitivity test against YGB36 revealed that the bacterial growth was not affected by any of the insecticides, and 11 fungicides out of 21 used. Collectively, our results clearly suggest that the strain YGB36 is considered as one of the potential biocontrol agents against anthracnose disease in red pepper.

• The Korean Journal of Pesticide Science
• /
• v.10 no.3
• /
• pp.210-217
• /
• 2006

The study was carried out to select the effective adjuvant as a photostabilizer for acetamiprid 5% SL(soluble concentrate) and to find its optimum content by using chemical and biological methods. Adjuvants used for the study were KS1 and KS2. Photodegradation test, insecticidal efficacies and residual analysis for the study were investigated. Although photodegradation rate of acetamiprid SL was decreased by addition of KS1 and KS2, the difference between KS1 and KS2 was not significant. As KS2 showed better efficacies against the cotton aphid (Aphis gossypii) and higher amount of residue on pepper than KS1, KS2 was selected as a photostabilizer for acetamiprid SL. Acetamipid SL with KS2 showed lower photodegradation rate, better efficacies against the cotton aphid (Aphis gossypii) and higher amount of residue on pepper as content of KS2 in acetamiprid SL was decreased. Therefore, it was concluded that the optimum content of KS2 was 0.1%. These results have demonstrated that the selected adjuvant could be used to enhance insecticidal activity and reduce spay dose of insecticide by protecting its photodegradation.

• Journal of Korean Society of Forest Science
• /
• v.94 no.6
• /
• pp.420-430
• /
• 2005

As the pine wilt disease spread rapidly over Korea in recent, aerial pesticide spraying to the infected pine stands increased abruptly. The increasing aerial pesticide application for control of the disease would result in disturbance of soil ecosystem in pine stands. This study was conducted to assess the disturbance, using field experiment in pine stands of Hongleong experimental forests in Seoul with BACI experimental design with three sprayed plots and three unsprayed plots of $25m^2$. We sprayed fenitrothion of 0.0335 kg a.i./ha over each of the sprayed plots, being the same as the pesticide residues of litters after aerial spraying. The pesticide had been applied on 4 June, 11 June, and 29 June in 2002, comparable with the dates of the aerial spraying in the previous year in Busan. We monitored population of soil organisms including arthropods, fungi, bacteria, and actinomycetes at two sampling days before pesticide application, at two sampling days during the application season, and at three sampling days after last application for two months since late May in 2002. The pesticide applications did not make any significant effect on the population of arthropods, fungi, bacteria, and actinomycetes in soils and on the structure of soil organism community, showing low probability of significant effects of the aerial pesticide application on soil organisms in pine stands.

• Korean Journal of Environmental Biology
• /
• v.27 no.1
• /
• pp.40-47
• /
• 2009

Heavy reliance on organosynthetic chemical methods to control agricultural pest tends to deteriorate and lower fertility of soil. We studied annual occurrence of earthworm in environment-friendly agroecosystem and attempted to determine the degree of soil contamination. Candidate bioindicators of earthworm in agroecosystem were selected through analysis of earthworm diversities. Depending on the degree of pesticide use, the fields were devided into conventional, less-pesticide, pesticide free, and organic fields. A nearby field not in agricultural use was chosen as a control. This study was carried out in the greenhouses (lettuce and grape) in 2006 and in orchards (apple, pear, peach, citrus and grape) in 2007. Earthworm was collected from 50 $\times$ 50 $\times$ 10 cm$^3$ of respective soil. We found 11 species from 5 genera and 3 families, and 12 species from 4 genera and 3 families in the greenhouses and in orchards, respectively. The contents of organic matter in soil in the greenhouses were variable but quite less so in orchards. Amynthas heteropodus occurred most frequently in both sites suggesting that it could be adopted as a bioindicator in agroecosystem in Korea.

• Research in Plant Disease
• /
• v.27 no.4
• /
• pp.129-136
• /
• 2021

Rice is responsible for the stable crop of 3 billion people worldwide, about half of Asian depends on it, and rice is grown in more than 100 countries. Rice diseases can lead to devastating economic loss by decreasing yield production, disturbing a stable food supply and demand chain. The most commonly used method to control rice disease is chemical control. However, misuse of chemical control can cause environmental pollution, residual toxicity, and the emergence of chemical-resistant pathogens, the deterioration of soil quality, and the destruction of biodiversity. In order to control rice diseases, research on alternative biocontrol is actively pursued including microorganism-oriented biocontrol agents. Microbial agents control plant disease through competition with and antibiotic effects and parasitism against plant pathogens. Microorganisms isolated from the rice rhizosphere are studied comprehensively as biocontrol agents against rice pathogens. Bacillus sp., Pseudomonas sp., and Trichoderma sp. were reported to control rice diseases, such as blast, sheath blight, bacterial leaf blight, brown spot, and bakanae diseases. Here we reviewed the microorganisms that are studied as biocontrol agents against rice diseases.

• Korean journal of applied entomology
• /
• v.48 no.2
• /
• pp.253-261
• /
• 2009

For the environment-friendly control of beet armyworm, Spodoptera exigua, in spring onion fields, we have examined an alternative application method. Twenty-five insecticides registered for spring onion were tested for control effect against the beet armyworm in the laboratory, then the best 9 chemical and a single biological insecticides were selected and compared with 2 new isolates of Bacillus thuringiensis in a polyvinyl house. After that, 4 chemical and 3 B. thuringiensis treatments were used in the field for the control of beet armyworm in the spring onion. Two application methods are used: one is triple treatments with the same chemical and the other is alternative application with different chemicals and B. thuringiensis for 7 days intervals. Indoxacarb WP - chlorfluazuron EC - B.t. var. kurstaki CAB141 and indoxacarb WP - methoxyfenozide + spinosad SC - Chlorfluazuron EC - B.t. var. aizawai CAB109, B.t. var. kurstaki CAB141 showed greater than 78% mortality of beet armyworm larvae and greater than 43% damage decrease in spring onions infested by beet armyworm. These results showed that alternative applications had higher control effect than any other applications. It was suggested that alternative applications with microbial biological agents such as B. thuringiensis might minimize the development of insecticide resistance and might be used as the environment-friendly control of the beet armyworm.