Combining Biocontrol Agents to Reduce the Variability of Biological Control

Two biocontrol agents, a yeast (Pichia guilermondii) and a bacterium (Bacillus mycoides), were tested separately and together for suppression of Botrytis cinerea on strawberry leaves. The aims of the research were to determine whether the use of their combination would broaden the environmental conditions under which biological control is effective, and to test the hypothesis that it would reduce the variability of control efficacy under diverse conditions. Applied separately, the biocontrol agents significantly inhibited spore germination, lesion formation, and lesion development at most temperatures, relative humidities, and spray-timing combinations (temperatures: 10, 15, 20, 23, 25, and 30°C; relative humidities: 78, 85, 96, and 100%; and spray-timings: 0, 4, and 7 days before inoculation). However, control efficacy was highly variable, and under certain combinations it was not adequate. Control efficacy achieved by the biocontrol agents applied separately ranged between 38 and 98% (mean 74%) and the coefficient of variation ranged from 9.7 to 75%. The mixture of Bacillus mycoides and Pichia guilermondii suppressed Botrytis cinerea effectively (80 to 99.8% control) under all conditions, and the coefficients of variation were as low as 0.4 to 9% in all cases. Thus, application of both biocontrol agents resulted in better suppression of Botrytis cinerea, and also reduced the variability of disease control. Application of more than one biocontrol agent is suggested as a reliable means of reducing the variability and increasing the reliability of biological control.

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Improving Biological Control by Combining Biocontrol Agents Each with Several Mechanisms of Disease Suppression

Phytopathology ◽

10.1094/phyto.2002.92.9.976 ◽

2002 ◽

Vol 92 (9) ◽

pp. 976-985 ◽

Cited By ~ 143

Author(s):

Ruth Guetsky ◽

D. Shtienberg ◽

Y. Elad ◽

E. Fischer ◽

A. Dinoor

Keyword(s):

Botrytis Cinerea ◽

Theoretical Explanation ◽

Significant Inhibition ◽

Disease Suppression ◽

Biocontrol Agents ◽

Yeast Cells ◽

Bacillus Mycoides ◽

Inhibitory Compound ◽

Bacterium Bacillus ◽

Quantitative Contribution

Two biocontrol agents, a yeast (Pichia guilermondii) and a bacterium (Bacillus mycoides), were tested separately and together for suppression of Botrytis cinerea on strawberry leaves and plants. Scanning electron microscopy revealed significant inhibition of Botrytis cinerea conidial germination in the presence of Pichia guilermondii, whereas Bacillus mycoides caused breakage and destruction of conidia. When both biocontrol agents were applied in a mixture, conidial destruction was more severe. The modes of action of each of the biocontrol agents were elucidated and the relative quantitative contribution of each mechanism to suppression of Botrytis cinerea was estimated using multiple regression with dummy variables. The improvement in control efficacy achieved by introducing one or more mechanisms at a time was calculated. Pichia guilermondii competed with Botrytis cinerea for glucose, sucrose, adenine, histidine, and folic acid. Viability of the yeast cells played a crucial role in suppression of Botrytis cinerea and they secreted an inhibitory compound that had an acropetal effect and was not volatile. Bacillus mycoides did not compete for any of the sugars, amino acids, or vitamins examined at a level that would affect Botrytis cinerea development. Viable cells and the compounds secreted by them contributed similarly to Botrytis cinerea suppression. The bacteria secreted volatile and non-volatile inhibitory compounds and activated the defense systems of the host. The nonvolatile compounds had both acropetal and basipetal effects. Mixture of Pichia guilermondii and Bacillus mycoides resulted in additive activity compared with their separate application. The combined activity was due to the summation of biocontrol mechanisms of both agents. This work provides a theoretical explanation for our previous findings of reduced disease control variability with a mixture of Pichia guilermondii and Bacillus mycoides.

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Biological Control of the Artillery Fungus, Sphaerobolus stellatus, with Trichoderma harzianum and Bacillus subtilis

Journal of Environmental Horticulture ◽

10.24266/0738-2898-19.1.21 ◽

2001 ◽

Vol 19 (1) ◽

pp. 21-23 ◽

Cited By ~ 1

Author(s):

Elizabeth A. Brantley ◽

Donald D. Davis ◽

Larry J. Kuhns

Keyword(s):

Biological Control ◽

Bacillus Subtilis ◽

Trichoderma Harzianum ◽

Biocontrol Agent ◽

Biocontrol Agents ◽

Biological Control Agents ◽

Oatmeal Agar ◽

Time Of Application ◽

Bacterium Bacillus Subtilis ◽

Bacterium Bacillus

Abstract Three strains of the fungus Trichoderma harzianum Rifai and two strains of the bacterium Bacillus subtilis (Ehrenberg) Cohn were evaluated for their ability to suppress colonization and sporulation of the artillery fungus (Sphaerobolus stellatus Tode:Pers.) on oatmeal agar. All five biological control agents inhibited growth of S. stellatus, but efficacy depended on time of application. Simultaneous inoculation of agar with S. stellatus and the biocontrol agents, as well as inoculation of biocontrol agents 14 days prior to S. stellatus, resulted in complete inhibition of S. stellatus. Inoculation of agar with biocontrol agents 14 days after inoculation with S. stellatus reduced, but did not completely suppress S. stellatus colonization and sporulation. In this experiment, gleba (spore masses) treated with all strains of T. harzianum and strain GBO3 of B. subtilis did not germinate, but 13% of gleba treated with strain MBI 600 of B. subtilis did germinate. Trichoderma harzianum was more effective than B. subtilis as a biocontrol agent.

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Biological control of Pythium mamillatum causing damping-off of cucumber seedlings by a soil bacterium, Bacillus mycoides

Microbiological Research ◽

10.1016/s0944-5013(11)80036-4 ◽

1995 ◽

Vol 150 (1) ◽

pp. 71-75 ◽

Cited By ~ 5

Author(s):

Bernard Paul ◽

Romond Charles ◽

Tej Bhatnagar

Keyword(s):

Biological Control ◽

Soil Bacterium ◽

Damping Off ◽

Bacillus Mycoides ◽

Cucumber Seedlings ◽

Bacterium Bacillus

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Biocontrol of Rhizoctonia Stem and Root Rot of Poinsettia with Burkholderia cepacia and Binucleate Rhizoctonia

Plant Disease ◽

10.1094/pdis.2002.86.1.47 ◽

2002 ◽

Vol 86 (1) ◽

pp. 47-53 ◽

Cited By ~ 20

Author(s):

J. Hwang ◽

D. M. Benson

Keyword(s):

Disease Control ◽

Root Rot ◽

Burkholderia Cepacia ◽

Crop Production ◽

Root Colonization ◽

Biocontrol Agent ◽

Biocontrol Agents ◽

Production Cycle ◽

Binucleate Rhizoctonia ◽

Control Application

Strategies for applying Burkholderia cepacia (strain 5.5B) and Pesta formulations of binucleate Rhizoctonia (BNR) isolates (BNR621 and P9023) were evaluated for biocontrol of Rhizoctonia stem and root rot of poinsettia caused by R. solani. During propagation, one application of B. cepacia suppressed stem rot, while application of either isolate of BNR did not. In contrast, after transplanting rooted poinsettias, one application of either BNR isolate was more effective for suppression of stem and root rot than application of B. cepacia. Sequential application of B. cepacia at propagation followed by a BNR isolate at transplanting was more effective over the crop production cycle than multiple applications of one biocontrol agent or combination application of both biocontrol agents. Root colonization by both biocontrol agents after transplanting rooted poinsettias was affected by application strategy. The least root colonization by both biocontrol agents occurred in the combination application. The highest root colonization by the BNR isolates was observed in the sequential application that provided the most effective disease control. Application of different biocontrol agents during the different production phases of poinsettia was effective for disease control, but understanding the interaction between biocontrol agents and root colonization was important to develop the best application strategy.

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Next Generation Biological Control: The Need for Integrating Genetics and Evolution

10.20944/preprints201911.0300.v1 ◽

2019 ◽

Cited By ~ 1

Author(s):

Kelley Leung ◽

Erica Ras ◽

Kim Ferguson ◽

Simone Ariëns ◽

Dirk Babendreier Babendreier ◽

...

Keyword(s):

Biological Control ◽

Biocontrol Agents ◽

Control Efficacy ◽

Ecological Principles ◽

Sequencing Strategy ◽

High Heritability ◽

Economic Perspectives ◽

Increasing Demand ◽

International Trade Laws ◽

Review Current

Biological control is widely successful for controlling pests, but effective biocontrol agents are now more difficult to obtain due to more restrictive international trade laws. Coupled with increasing demand, the efficacy of existing and new biocontrol agents needs to be improved with genetic and genomic approaches. Although they have been underutilised in the past, applying genetic and genomic techniques is becoming more feasible from both technological and economic perspectives. We review current methods and provide a framework for using them, incorporating evolutionary and ecological principles. First, it is necessary to identify which biocontrol trait to select and in what direction. Next, the genes or markers linked to these traits need be determined to better target their selection, followed by how to implement this information into a breeding program. Choosing a trait can be assisted by modelling to account for the proper agro-ecological context, and by knowing which traits have sufficiently high heritability values. We provide guidelines for designing genomic strategies in biocontrol programs, which depends on the organism, budget, and desired objective. Genomic approaches start with genome sequencing and assembly. We provide a guide for deciding the most successful sequencing strategy for biocontrol agents. Gene discovery involves quantitative trait loci (QTL) analyses, transcriptomic and proteomic studies, and gene editing. Improving biocontrol practices include marker-assisted selection, genomic selection and microbiome manipulation of biocontrol agents, and monitoring for genetic variation during rearing and post-release. We conclude by identifying the most promising applications of genetic and genomic methods to improve biological control efficacy.

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Biological Control of Root Pathogens in Rockwool and Other Hydroponic Systems

HortScience ◽

10.21273/hortsci.30.4.750b ◽

1995 ◽

Vol 30 (4) ◽

pp. 750B-750

Author(s):

M.L. Matheny

Keyword(s):

Biological Control ◽

Environmental Conditions ◽

Crop Production ◽

Biocontrol Agent ◽

Initial Period ◽

Biocontrol Agents ◽

Additional Advantage ◽

Root Diseases ◽

Edaphic Conditions ◽

Hydroponic Systems

One of the main difficulties in controlling root diseases biologically has been the inability of biocontrol agents to establish and persist in the rhizosphere. The inability of biocontrol agents to establish and persist is often attributed to competition from indigenous microorganisms for space and nutrients and to fluctuations in environmental conditions. The use of biocontrol agents over the entire geographic range of a crop also has been limited by differences in environmental and edaphic conditions from field to field and region to region. An advantage of hydroponic crop production in greenhouses is that environmental conditions such as temperature, moisture, pH, and growth medium can be consistently controlled in a house and from site to site. An additional advantage of many hydroponic systems is that they are virtually sterile upon planting. This initial period of virtual sterility greatly reduces competition for an introduced biocontrol agent. In addition, these systems are usually pathogen-free upon planting allowing the establishment of a biocontrol agent prior to pathogen introduction. Last, the temperatures, high moisture levels, and pH ranges of hydroponic systems can be ideal for the proliferation of many biocontrol agents. With all of these advantages for the use of biocontrol agents in hydroponic systems, our company, and many labs around the world, have focused their attention on developing biological control agents for these systems. I will provide a review of research focused on controlling root diseases of vegetables grown in rockwool and other hydroponic systems.

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Optimized fluorescent proteins for the rhizosphere‐associated bacterium Bacillus mycoides with endophytic and biocontrol agent potential

Environmental Microbiology Reports ◽

10.1111/1758-2229.12607 ◽

2018 ◽

Vol 10 (1) ◽

pp. 57-74 ◽

Cited By ~ 3

Author(s):

Yanglei Yi ◽

Elrike Frenzel ◽

Jan Spoelder ◽

J. Theo M. Elzenga ◽

Jan Dirk van Elsas ◽

...

Keyword(s):

Biocontrol Agent ◽

Fluorescent Proteins ◽

Bacillus Mycoides ◽

Bacterium Bacillus

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Biological and Host Range Characteristics of Lysathia flavipes (Coleoptera: Chrysomelidae), a Candidate Biological Control Agent of Invasive Ludwigia spp. (Onagraceae) in the USA

Insects ◽

10.3390/insects12050471 ◽

2021 ◽

Vol 12 (5) ◽

pp. 471

Author(s):

Angelica M. Reddy ◽

Paul D. Pratt ◽

Brenda J. Grewell ◽

Nathan E. Harms ◽

Ximena Cibils-Stewart ◽

...

Keyword(s):

Biological Control ◽

Host Range ◽

Plant Species ◽

Biocontrol Agent ◽

Biological Control Agent ◽

Control Agent ◽

Native Plant ◽

Native Plant Species ◽

The Usa ◽

Physical And Chemical

Exotic water primroses (Ludwigia spp.) are aggressive invaders in aquatic ecosystems worldwide. To date, management of exotic Ludwigia spp. has been limited to physical and chemical control methods. Biological control provides an alternative approach for the management of invasive Ludwigia spp. but little is known regarding the natural enemies of these exotic plants. Herein the biology and host range of Lysathia flavipes (Boheman), a herbivorous beetle associated with Ludwigia spp. in Argentina and Uruguay, was studied to determine its suitability as a biocontrol agent for multiple closely related target weeds in the USA. The beetle matures from egg to adult in 19.9 ± 1.4 days at 25 °C; females lived 86.3 ± 35.6 days and laid 1510.6 ± 543.4 eggs over their lifespans. No-choice development and oviposition tests were conducted using four Ludwigia species and seven native plant species. Lysathia flavipes showed little discrimination between plant species: larvae aggressively fed and completed development, and the resulting females (F1 generation) oviposited viable eggs on most plant species regardless of origin. These results indicate that L. flavipes is not sufficiently host-specific for further consideration as a biocontrol agent of exotic Ludwigia spp. in the USA and further testing is not warranted.

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Synergistic Effect of Combined Application of a New Fungicide Fluopimomide with a Biocontrol Agent Bacillus methylotrophicus TA-1 for Management of Gray Mold in Tomato

Plant Disease ◽

10.1094/pdis-01-19-0143-re ◽

2019 ◽

Vol 103 (8) ◽

pp. 1991-1997 ◽

Cited By ~ 3

Author(s):

Xiaoxue Ji ◽

Jingjing Li ◽

Zhen Meng ◽

Shouan Zhang ◽

Bei Dong ◽

...

Keyword(s):

Field Experiments ◽

Biocontrol Agent ◽

Severe Disease ◽

Combined Treatment ◽

Field Trials ◽

Antimicrobial Activities ◽

Gray Mold ◽

Control Efficacy ◽

Bacillus Methylotrophicus

Gray mold caused by Botrytis cinerea can be a severe disease of tomato infecting leaves and fruits of tomato plants. Chemical control is currently the most effective and reliable method; however, application of fungicides has many drawbacks. The combination of biological control agents with newly developed fungicides may be a practicable method to control B. cinerea. Fluopimomide is a newly developed fungicide with a novel mode of action. Bacillus methylotrophicus TA-1, isolated from rhizosphere soil of tomato, is a bacterial strain with a broad spectrum of antimicrobial activities. Little information is currently available about the effect of fluopimomide and its integrated effect on B. cinerea. Therefore, laboratory, pot, and field experiments were carried out to determine the effects of fluopimomide alone and in combination with B. methylotrophicus TA-1 against gray mold on tomato. The in vitro growth of B. methylotrophicus TA-1 was unaffected by 100 mg liter−1 fluopimomide. Inhibition of B. cinerea mycelial growth was significantly increased under combined treatment of fluopimomide and B. methylotrophicus TA-1. In greenhouse experiments, efficacy against gray mold was significantly greater by an integration of fluopimomide and B. methylotrophicus TA-1 than by either alone; control efficacy of fluopimomide at 50 and 100 g ha−1 in combination with B. methylotrophicus TA-1 at 108 colony-forming units (cfu) ml−1 reached 70.16 and 69.32%, respectively, compared with the untreated control. In both field trials during 2017 and 2018, control efficacy was significantly higher for the combination of fluopimomide at 50 and 100 g ha−1 in combination with B. methylotrophicus TA-1 than for either treatment alone. The results from this study indicated that integration of the new fungicide fluopimomide with the biocontrol agent B. methylotrophicus TA-1 synergistically increased control efficacy of the fungicide against gray mold of tomato.

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