New biocontrol method for parsley powdery mildew by the antifungal volatiles-producing fungus Kyu-W63

Biocontrol of parsley powdery mildew, caused by Oidium sp., was examined for 3 years under greenhouse conditions using a filamentous fungus, strain Kyu-W63, which produces antifungal volatiles. Kyu-W63 was cultured on potato-dextrose agar in sterile polycarbonate pots and then placed at 30-cm intervals in the center of each ridge in 1998, 1999, and 2000. This Kyu-W63 treatment significantly inhibited disease severity compared to control plots.     

Mycoherbicides and other biocontrol agents for Senecio spp

Classical biocontrol of Senecio jacobaea (ragwort) has generally utilised herbivorous insects, although the nisi Puccinia expansa has also been considered. Although this rust is specific and damaging in the glasshouse. It has not been used in the field. Research into the ecophysiology of Senecio vulgaris (groundsel) infected by the rust Puccinia lagenophorae has revealed the extent to which the effects of infection are dependent on environmental factors. The damage caused by rust is enhanced under mild drought conditions, during periods of frost in winter and by competition between groundsel and neighbouring plants, bui is reduced by nutrient deficiency. Rust injury is also greatly increased by secondary infection of pustules by necrotrophic fungi. Such secondary infection can be achieved artificially with a range of opportunistic necrolrophs and can selectively kill groundsel: the effective inoculum dose of both fungi is significantly reduced. Attempts to apply our understanding of rust-necrotroph injury to ragwort have been partially successful but we have not succeeded in causing significant mortality of this host. This paper discusses these, and other weed—pathogen—environment interactions, and their possible application to biocontrol.     

Impact of Fusarium oxysporum on the holoparasitic weed Phelipanche ramosa: biocontrol efficacy under field-grown conditions

Under the changing agro-climatic conditions of western Europe, the parasitic weed Phelipanche ramosa infests host crops such as tomato, hemp, tobacco and oilseed rape at an increasing rate. A Fusarium oxysporum isolate (FOG), that had effectively reduced the parasite's incidence under controlled environmental conditions, was tested in different granular formulations (pesta granules, alginate pellets) on P. ramosa parasitising tobacco under field-grown conditions. FOG reduced number and biomass of P. ramosa shoots by between 50% and 70% in three consecutive years (2006–2008). A single pesta application did not show consistent results throughout seasons; 50% reduction of P. ramosa biomass (DM) in the first year could not be repeated in the following years (20–30%). An alginate formulation applied alone performed better. However, a combination of pesta granules with alginate pellets had the highest reliable control efficacy (60–70%) of all treatments in two seasons, compared with the untreated control. Fungal population counts in soil samples did not show a close correlation to biocontrol efficacy. To understand field performance of this biocontrol agent, additional glasshouse and laboratory studies were conducted using soil from the experimental site. The glasshouse study revealed some fungistatic effects of the field soil that partly explain the reduced efficacy (-40%) in the field compared with results obtained under controlled conditions. Results show the potential of FOG for P. ramosa control. Because formulation affected the biocontrol efficacy, it may be worthwhile to test how the delivery system can be changed in order to achieve increased disease development in the field.     

Bioinformatics tools for the discovery of new lipopeptides with biocontrol applications

As conventional or chemical pesticides have negative impact on environment and health of both farmer and consumers, it becomes relevant to develop alternative solutions to limit their use. In this context, innovative strategies to accelerate the development of biocontrol agents are welcome. For a decade of years, it has been demonstrated that lipopeptides are very efficient weapons against fungi responsible for crop diseases. Lipopeptides are secondary metabolites, produced by many microorganisms including beneficial rhizobacteria. The lipopeptide biosynthetic pathways include nonribosomal peptide synthetases. These modular enzymatic complexes work as assembly lines to build the peptides step by step, leading to the production of original peptide compounds with specific features as the presence of non proteinogenic monomers and cyclic and branched structures. In this paper, Florine and Norine bioinformatics tools, especially dedicated to non-ribosomal synthetases and their products are presented. Their use is mainly focused on the discovery of lipopeptides produced by Bacillus or Pseudomonas because they seem to represent a versatile reservoir of active secondary metabolites with promising activities for applications in phytosanitary area.     

Potential for classical biocontrol of silverleaf nightshade in the Mediterranean Basin

Unlike biocontrol of insect pests, biocontrol of invasive weeds is not largely studied in Eurasia, but remains an ecologically sound approach to invasive species management. The case study of silverleaf nightshade ( Solanum elaeagnifolium ) is a good example of a New World weed which has been introduced and is spreading over the Mediterranean Basin. S. elaeagnifolium economically impacts agricultural areas by competing with cereal crops, damaging pastures, and infesting meadows and roadsides. This paper deals with classical biological control of S. elaeagnifolium in the Mediterranean basin with natural enemies from the region of origin of the target plant, using studies conducted on other continents. Natural enemies are listed and their capability to attack and control the target plant is discussed. Special attention is devoted to Leptinotarsa texana and L. deflecta , chrysomelid beetles already released with success against S. elaeagnifolium in South Africa, one of the five Mediterranean-type regions of the world.     

Pest control by predators and parasites

The feasibility of controlling the two-spotted spider mite in apple orchards by inundative releases of the phytoseiid predatorPhytoseiulus persimilis, was studied in a field trial in northern Israel. Half a million predators released per acre, maintained high populations forca 2 months until the spider mite population dropped below the economic threshold.P. persimilis demonstrated a dispersal capacity of at least 90 m from its original release site. The ability of the predator to switch to alternative prey (the European red mite) and the economic feasibility of this non-chemical approach to spider mite control, are discussed.     

Peanut priming induced by biocontrol agents

Selected strains of rhizobacteria induce systemic resistance in plant (ISR), enhancing the capacity to mobilize infection-induced cellular defense responses (priming). Bacillus sp. CHEP5 and Pseudomonas sp BREN6 strains reduced root and stem wilt disease severity caused by Sclerotium rolfsii in Arachis hypogaea L. Strains inoculation increased the activity of phenylalanine ammonia-lyase and peroxidase, after pathogen-challenge, indicating priming. CHEP5 primes plants to produce more ethylene upon stimulation with ACC. A. hypogaea L is an ISR-positive plant and BREN6 and CHEP5 strains enhance the plant’s defense capacity by priming for potentiated activity of defense proteins and ACC-converting capacity.     

Evaluation of biocontrol agents for managing root diseases on hydroponically grown tomato

Journal of Plant Diseases and Protection - The effect of the bacterial strain Pseudomonas fluorescens 5.014 together with three commercial biocontrol products (Binab T, Gliomix and Mycostop)...     

水葫芦生防菌Cercospora piaropi的病理学特性

尾孢菌属的Cercospora piaropi是一种有潜力开发成为防除水葫芦的生物除草剂的真菌。水葫芦原生叶片从被C．piaropi感染到完全死亡，需要约6周时间。C．piaropi接种水葫芦的适宜孢子浓度为10^5CFU/ml，适宜保湿时间为24h。30℃时C．piaropi感染水葫芦的原生叶片病害严重度最高。除水葫芦和鸭舌草外，cpiaropi对其他被测农作物和杂草均不产生病理作用，表现出较强的专一性。     

Technical and commercial aspects of biocontrol products

The global agrochemical market in 1991 was $26800 million, yet biological products were reported to account for only $120 million of sales per annum—less than 0.5 % of the total. The majority of these sales are attributed to bio-insecticides of which Bacillus thuringiensis accounts for over 90%, but B. thuringiensis could be described as a biologically produced insecticide, rather than a true biocontrol agent. Biological products have technical limitations, including extreme specificity, sensitivity to environmental factors and problems with robustness of the formulations, but ironically, it is these limitations which also give biological control an image of environmental acceptability. Nonetheless, some of the limitations will be overcome and sales will increase, but primarily in niche situations such as the control of soil-borne diseases and the control of insect pests showing resistance to agrochemicals. In order for significant inroads to be made into such niche markets it is imperative that progress with biological products is not impaired by over-regulation, and a rational approach by all regulatory bodies is required. Overall, though, agrochemicals are likely to continue to be the major method of crop protection for the foreseeable future, and the biological control field now needs clear, well-defined goals if current successful niche products can be the basis for future success rather than a limited experiment in alternative technology.     

Host specificity of Puccinia canaliculata,a potential biocontrol agent for Cyperus esculentus

Aim was to clarify the rust fungusPuccinia canaliculata for release in a new environment where it may be utilized as a microbial herbicide. A strain of the rust was introduced from the USA into the Netherlands and kept in quarantaine. The susceptibility ofCyperus esculentus and several other species of the Cyperaceae was tested. C. esculentus leptostachyus from five locations was susceptible toP. canaliculata. C. esculentus of a yet unidentified biotype from two locations was moderately susceptible (fewer and smaller pustules than on leptostachyus), whereas plants of the same biotype from a third location were resistant to the rust.C. esculentus esculentus (from one location) andC. esculentus sativus (a crop) were also resistant to the rust. C. albostriatus, C. alternifolius, C. flavescens, C. rotundus, Carex hirta, Eleocharis palustris, andScirpus maritimus were resistant toP. canaliculata. OnCyperus fuscus, P. canaliculata produced very small urediniosori (less then 1 mm in diameter); the sori were surrounded by a zone of necrotic plant tissue.From the observations onC. fuscus we concluded that the (potential) host range ofP. canaliculata is wider than we originally expected. For safety reasons, it was decided not to release it in the Netherlands.     

An effective biocontrol bioformulation against Phytophthora blight of pepper using growth mixtures of combined chitinolytic bacteria under different field conditions

Phytophthora blight of pepper caused by Phytophthora capsici has devastating consequences when combined with other pathogens, including Rhizoctonia solani, Fusarium oxysporum, and Fusarium solani. In order to develop a field-effective biocontrol strategy against Phytophthora blight of pepper, three chitinolytic bacteria, Serratia plymuthica strain C-1, strongly antagonistic to P. capsici, Chromobacterium sp. strain C-61, strongly antagonistic to R. solani, and Lysobacter enzymogenes strain C-3, antagonistic to R. solani and Fusarium spp., were selected. In pot studies, application of cultures combining the three bacterial strains effectively suppressed Phytophthora blight more than application of any single bacterial strain. Bioformulations developed from growth of the strains in a simple medium containing chitin under large batch conditions resulted in effective control in field applications. Efficacy of the bioformulated product depended on both the dose and timing of application. Although the undiluted product suppressed Phytophthora blight under all field conditions, a 10-fold diluted product was effective in solar-sterilized greenhouses and in fields with crop rotation. These results suggest that the developed product could be a new effective system to control Phytophthora blight disease in pepper.     

Assessment of in vivo screening systems for potential biocontrol agents of Gaeumannomyces graminis

A screening programme was used to search for biocontrol agents against Gaeumannomyces graminis causing take-all disease of wheat. Of the 1800 rhizosphere microorganisms tested, 10% controlled the disease in a secondary screen. The 30 most effective isolates were further investigated for mode of action. Although 72% of the sites sampled for antagonistic microbes were planted to continuous cereals, they yielded only 23% of the most effective isolates. Of all the isolates selected, 63% belonged to the genera Bacillus, Pseudomonas and Penicillium; Beauveria and Rhodococcus were also antagonistic. Fluorescent pseudomonads, all producing siderophores in low-iron medium, accounted for 23% of the isolates. Over 50% of strains produced β-glucanases and chitinases. Less than 50% of the strains selected by the in vivo screen inhibited G. graminis in agar plate tests. In the gnotobiotic system used, the Pseudomonas strains were faster in colonizing the wheat roots than the majority of the Bacillus and fungal strains.     

噬菌体防治植物细菌性病害研究进展

植物病原细菌是限制农业生产的主要原因之一,作物受害严重,造成巨大的经济损失。化学防治、农艺防治以及抗病育种等方法,对植物细菌性病害实现了较好的防治,但是这些方法各自存在着不足之处。噬菌体无处不在,有细菌的地方就有噬菌体。噬菌体具有特异性,可以自我复制,相比于植物细菌性病害的其他防治方法,噬菌体防治环境友好,且制造成本低廉,越来越多的研究学者尝试用噬菌体控制细菌性病害,以补充传统防治方法的不足。本文列举了一些较为严重的植物细菌性病害的为害、传统的防治办法,并总结了已有的噬菌体防治手段以及噬菌体防治的发展前景。     

Combining proteolytic and phloroglucinol-producing bacteria for improved biocontrol of Pythium-mediated damping-off of sugar beet

Pseudomonas fluorescens F113 and Stenotrophomonas maltophilia W81 protect sugar beet from Pythium -mediated damping-off through production of the antifungal secondary metabolite 2,4-diacetylphloroglucinol and extracellular proteolytic activity, respectively. In this study, the two biocontrol strains were combined in a consortium, with the objective of improving upon the level of protection achieved when using each strain singly. Growth and in vitro production of 2,4-diacetylphloroglucinol by F113 and extracellular lytic enzymes by W81 were not affected when inoculated in combination. The abilities of W81 and F113 to colonize the rhizosphere of sugar beet were essentially similar when the two strains were applied singly or coinoculated onto seeds in a 1 : 1 ratio, both in natural soil microcosms and under field conditions. Concomitantly, single inoculation with W81 or F113 effectively prevented colonization of sugar beet seeds by Pythium spp. in soil microcosms, without the necessity for combining both strains. However, this parity was not reflected in seed emergence where the combination of W81 and F113 significantly enhanced final sugar beet stands (to the level achieved with chemical pesticides) under microcosm conditions at 28 days after sowing. In a field experiment, the only inoculation treatment capable of conferring effective protection of sugar beet was that in which W81 and F113 were coinoculated, and this treatment proved equivalent to the use of chemical fungicides. In conclusion, when compared with single inoculations of either biocontrol strain, the combined use of a phloroglucinol-producing P. fluorescens and a proteolytic S. maltophilia improved protection of sugar beet against Pythium -mediated damping-off.     

Fluorescent Pseudomonas isolate E11.3 as biocontrol agent for Pythium root rot in tulips

FluorescentPseudomonas isolates were obtained from Pythium-diseased tulip roots or rhizospheres. A selection of these isolates was tested for root rot-suppressing capabilities, using tulip cultivar Paul Richter (ice-tulip) as host andPythium ultimum P17 as pathogen. With isolate E11.3 root rot suppression was consistently found, but the extent of the effects varied from experiment to experiment. Beneficial effects were obtained after introduction of the bacteria either by mixing them through the soil or by dipping the bulbs in a bacterial suspension, immediately before planting. Application of bacteria in methylcellulose also reduced disease, but is of no practical value as methylcellulose by itself increased disease. In steamed soil, disease was more severe than in natural soil. In both circumstances, however, beneficial effects of bacterization with E11.3 were observed.Samenvatting Fluorescerende pseudomonaden werden geïsoleerd van tulpewortels of uit de rhizosfeer daarvan. Een aantal van deze isolaten is getoetst op wortelrot-onderdrukkend vermogen in een experimenteel systeem met tulpecultivar Paul Richter (vriestulp) als waardplant enPythium ultimum isolaat P17 als pathogeen. Wortelrotonderdrukking werd consequent waargenomen na bacterisatie metPseudomonas isolaat E11.3; de mate waarin rotonderdrukking optrad verschilde echter van experiment tot experiment. Bacterisatie vond plaats òf door de bacteriën door de grond te mengen òf door de bollen vlak voor het planten in een bacteriesuspensie te dompelen. Met beide methoden werden positieve resultaten bereikt. Toedienen van bacteriën in methylcellulose leidde ook tot reductie van de ziekte, maar heeft geen practische betekenis aangezien methylcellulose op zich de ziekte doet toenemen. Wortelrot was ernstiger in gestoomde dan in nietgestoomde grond, maar in beide omstandigheden werkte E11.3 wortelrotonderdrukkend.