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1.
Biological control of Agrobacterium tumefaciens using the K84 strain of A. radiobacter has been practised in Spain since 1979. Strain K84 is produced in Sevilla by the Agricultural Research Service and is mixed with peat. This formulation is authorized for use on stone fruits and roses, since results of various trials on rootstocks of these crops have shown that K84 is effective in controlling the disease in naturally infected nursery soil, as well as in experimental tests carried out on artificially inoculated soil. Results of biological control trials have shown that K84 has some effect on A. tumefaciens strains resistant to agrocin 84. Factors other than susceptibility to agrocin 84 influence the efficacy of biological control. This was demonstrated by using a K84 agrocin non-producer strain which proved effective against both resistant and susceptible strains. Biological control on apple or pear is not yet authorized in Spain due to a paucity of data on field trials. However, initial pot tests showed good K84 activity on these hosts, against Spanish strains of A. tumefaciens. On grapevine, most of the A. tumefaciens strains that were isolated belong to biotype 3 and are resistant to agrocin 84. Because the disease is systemic on this species the use of K84 is not authorized.  相似文献   

2.
E. TAPIO 《EPPO Bulletin》1987,17(4):577-580
Studies on biological control of plant pathogens in Finland were started by Pohjakallio in the 1950s, concentrating especially on the microbes parasitizing fungal sclerotia. At the turn of the 70s, Kallio studied the protective effect of Finnish isolates of Phlebia gigantea against the most important forest pathogen Heterobasidion annosum with positive results. The preparation was put on the market. Later in the 1970s, the observation by Tahvonen that Finnish light-coloured peat had an inhibitory effect on the infection of plants by some seed and soil-borne fungal pathogens led to further investigations. Of the microbes isolated from peat, Streptomyces spp. proved the most effective antagonists in both in vitro and in vivo tests. Studies are in progress with S. griseoviridis and several other fungal and bacterial antagonists as potential biocontrol agents against some seed and soil-borne pathogens and storage diseases.  相似文献   

3.
Biological control efficiency of an antagonistic, endophytic strain of Bacillus subtilis (strain BB) was evaluated against three strains of the black rot pathogen, Xanthomonas campestris pv. campestris (Xcc), in four Brassica crops (cabbage, cauliflower, rape and broccoli) grown during three consecutive growing seasons and on two soil types, in two different areas in Zimbabwe. Strain BB controlled the disease caused by strain Xcc B-147 in all Brassica crops during the dry and short rainy seasons. A similar effect was observed in cabbage using the strain Xcc 33908. Biological control was effective in broccoli, but not in cabbage and rape during the main rainy season in clay loam soil and limited biological control effect was still observed when these crops were grown in sandy loam soil. The endophytic colonisation of cabbage roots by strain BB was confirmed by immuno-blotting during the whole growing season. Biological control of black rot with strain BB is discussed in relation to its effect on Xcc strains, Brassica crops and to the effect of weather and soil conditions.  相似文献   

4.
Biological control has already achieved certain results in Hungary, especially against soil-borne fungi and glasshouse pests. Nevertheless, experience has shown that locally found biological agents, however effective, could not be developed into registered, ready-for-sale plant protection products because of the lack of companies willing to invest. Biological control in Hungary is therefore limited to the conservation of natural antagonistic flora and fauna and to the application of imported biopesticides and bioagents, which are subject in Hungary to a registration procedure similar to that for chemical plant protection products. Current work includes the development of an anti-nematode product from a local strain of Arthrobotrys oligospora, application techniques for a local mirid Dicyphus hyalinipennis against insect pests, studies with native and imported strains of the nematodes Steinernema and Heterorhabditis against soil-borne insect pests, and introduction techniques for the chrysomelid Zygogramma sutularis against the weed Ambrosia elatior.  相似文献   

5.
Biological control methods introduced and developed for Belarussian glasshouse crops are described. The agents used against arthropod pests include the natural enemies Phytoseiulus persimilis, Encarsia formosa and Amblyseius spp., the fungi Verticillium lecanii, Beauveria bassiana and Aschersonio, and the preparation Bitoxibacillin (based on Bacillus thuringiensis var. thuringiensis). Against fungal pathogens, Trichodermin (based on Trichuderma Iignorum) and peat oxyhumates are used.  相似文献   

6.
A real-time PCR assay specific for Sclerotium cepivorum, the causal agent of white rot in onions, was developed for use with a new DNA extraction method capable of processing up to 1?kg of soil in weight. The assay was specific for S. cepivorum when tested against 24 isolates representative of 14 closely related species and other pathogens of onion. The assay was highly sensitive when used with soil DNA extracted using the new DNA extraction procedure. In three different field soils tested, a good relationship between cycle threshold (Ct) and number of sclerotia was observed (R2?=?0.89). Twenty-nine soil samples from onion and leek crops were obtained and the pathogen was detected in four samples. All four positive samples were associated with current or past outbreaks of white rot of onion. Additional assays were also used on the 29 field soil samples, Botrytis aclada and Rhizoctonia solani AG8 were also detected, in one soil sample each. Rhizoctonia solani AG2-1 was more widespread and was detected in eight different soil samples. The method is therefore suitable to quantify levels of S. cepivorum in soil samples, with the added advantage that the technique allows other soil pathogens of interest to be assayed from the same DNA sample. The bulk soil DNA extraction method described here has the potential to be used to detect soil-borne pests and pathogens for other crops in a wide range of soil types.  相似文献   

7.
Effects of crop rotation on the incidence of soil-borne pathogens and on the performance of potato were investigated in five field experiments. Rotations differed in cropping frequency of potato and in crop sequence.Incidence of stem canker caused byRhizoctonia solani was strongly influenced by the cropping frequency of potato and not by crops with which the potato was alternated in the rotation. Cropping frequency of potato also affected the occurrence of black scurf, but less pronounced than for stem canker. The antagonistVerticillium bigutatum slightly reducedR. solani (black scurf) in plots on sandy soil continuously cropped with potato. Incidence of stem canker was also strongly affected by granular nematicides applied to the soil, nitrogen level and the cultivar grown.  相似文献   

8.
The use of Brassica crops as green manure in the so-called biofumigation treatment has been successfully exploited for the management of soilborne pathogens and is gaining interest particularly in the case of less intensive agricultural systems. A study was undertaken to investigate possible negative side-effects of biofumigation in order to prevent possible damage caused by wilt pathogens able to attack both plants used for biofumigation as well as agricultural crops. To do so, firstly the response of different Brassicas, including some used in biofumigation, to the formae speciales of Fusarium oxysporum known for being pathogenic on Brassica crops was evaluated. Secondly, the effect of green manure treatments on yield, quality of crops, and inoculum densities, infection and survival of Fusarium oxysporum f. sp. conglutinans and F. oxysporum f. sp. raphani was evaluated. In the second part of the work, four Brassica crops, selected for their response (susceptibility or resistance) to F. oxysporum f. sp. conglutinans and to F. oxysporum f. sp. raphani were evaluated in order to determine their response to the two pathogens during subsequent crops grown in soil where plants were incorporated as green manure into the soil at the end of each cycle. Moreover, the dynamics of the populations of F. oxysporum f. sp. conglutinans and F. oxysporum f. sp. raphani in the soil after several biofumigation cycles was studied. Many of the Brassica crops used for biofumigation tested were susceptible to F. oxysporum f. sp. conglutinans and or to F. oxysporum f. sp. raphani. Green manure treatment, carried out by growing nine cycles of biocidal plants, with a short crop cycle of 30–35 days, did not reduce Fusarium wilts on susceptible Brassica hosts. The population of the pathogen was partially increased as a result of the incorporation of tissues of the susceptible plants. When Brassica crops grown were resistant to the two F. oxysporum pathogens used for soil infestation, green manure simulation did inhibit both pathogens, thus confirming its biocidal activity. The results obtained under our experimental conditions show that biofumigation treatment is not applicable for soil disinfestation on crops susceptible to the same formae speciales of F. oxysporum affecting Brassica species used for biofumigation. Brassica crops resistant to Fusarium yellows should be grown where biofumigation is applied. Moreover, alternation of crops used for biofumigation should be encouraged.  相似文献   

9.
The effect of different soil amendments and biological control agents on soil-borne root diseases that cause significant economic losses in organic and other soil-based tomato production systems (Pyrenochaeta lycopersici and Verticillium albo-atrum) was compared. Organic matter inputs (fresh Brassica tissue, household waste compost and composted cow manure) significantly reduced soil-borne disease severity (measured as increased root fresh weight) and/or increased tomato fruit yield, with some treatments also increasing fruit number and/or size. Soil biological activity also increased with increasing organic matter input levels and there were significant positive correlations between soil biological activity, root fresh weight and fruit yield. This indicates that one mechanism of soil-borne disease control by organic matter input may be increased competition by the soil biota. Chitin/chitosan products also significantly reduced soil-borne disease incidence and increased tomato fruit yield, number and/or size, but had no effect on soil biological activity. Biological control products based on Bacillus subtilis and Pythium oligandrum and commercial seaweed extract (Marinure) and fish emulsion (Nugro)-based liquid fertilisers had no positive effect on soil-borne disease incidence and fruit yield, number and size. The use of ‘suppressive’ organic matter inputs alone or in combination with chitin/chitosan soil amendments can therefore be recommended as methods to control soil-borne diseases in organic and other soil-based production systems.  相似文献   

10.
Biological control of soil-borne pathogens by arbuscular mycorrhizal (AM) fungi has been repeatedly demonstrated. However, their role in the control of above-ground hemibiotrophic pathogens is less conclusive. Here, we investigated in vitro the impact of an AM fungus on Phytophthora infestans in potato plants. The leaf infection index was decreased in mycorrhizal potato plants. Real-Time Quantitative PCR revealed the induction of two pathogenesis related genes (PR1 and PR2) in the leaves of mycorrhizal plants shortly after infection with P. infestans. These results suggested a systemic resistance in mycorrhizal plants, related to the priming of the two PR genes in potato.  相似文献   

11.
Light-coloured Sphagnum fuscum peat is the substrate most widely used in glasshouses in Finland. A number of Streptomyces strains which are strongly antagonistic against a number of soil and seed-borne fungal pathogens, both in vitro and in vivo, have been isolated from light-coloured peat. Seed dusting with Streptomyces prevented or reduced damping-off and foot-rot disease caused by Alternaria brassicicola and Rhizoctonia solani on crucifers. Seed treatment slightly increased yields of cereals in fields experiments. Spraying the substrate with a suspension of Streptomyces reduced root diseases on cucumbers caused by Pythium, and in many cases successfully prevented fusarium wilt of carnations. A dry powder preparation has been made from the Streptomyces isolates, and applied at a dose of 5-10 g kg-1 in seed dusting, and 0.1-10 g 100 m-2 when spraying the substrate. The microbe was most effective in peat soil, although good results have also been obtained in fine sand and clay soils.  相似文献   

12.
The genus Verticillium includes several species that attack economically important crops throughout the world. The control of Verticillium spp. becomes especially difficult when they form microsclerotia that can survive in the field soil for several years. It has been common practice to fumigate soil with chemicals such as methyl bromide and/or chloropicrin to control soil‐borne fungal pathogens. Other chemicals that are used against Verticillium spp. are the antifungal antibiotic aureofungin, the fungicides benomyl, captan, carbendazim, thiram, azoxystrobin and trifloxystrobin and the plant defence activator acibenzolar‐S‐methyl. However, the potential risks involved in applying phytochemicals to crop plants for both the environment and human health, together with their limited efficacy for controlling Verticillium‐induced diseases, support the need to find alternatives to replace their use or improve their efficacy. Soil amendment with animal or plant organic debris is a cultural practice that has long been used to control Verticillium spp. However, today the organic farming industry is becoming a significant player in the global agricultural production scene. In this review, some of the main results concerning the efficacy of several soil amendments as plant protectors against Verticillium spp. are covered, and the limitations and future perspectives of such products are discussed in terms of the control of plant diseases. Copyright © 2009 Society of Chemical Industry  相似文献   

13.
Understanding the distribution pattern of the Fusarium species can help prevent crop diseases and large yield losses. While several approaches have been used to control soil-borne pathogens, soil solarisation has shown promising results in managing these pathogens. The main objectives of this study were to: (i) describe the biogeography of Fusarium species in four different climatic zones in Iran and (ii) explain the effect of soil solarisation on main pathogenic Fusarium species in wheat grains, beans and date palms. A total of 12 sub-samples were collected from four different climatic zones including, Rasht (humid), Zanjan (semi-arid), Isfahan (extra-arid) and Ahwaz (arid). For precise identification, molecular-phylogenetic analyses of the species were also performed. From these four sites 17 Fusarium species were recovered. F. solani complex, F. oxysporum and F. equiseti were the only species found in all four regions; whereas F. compactum, F. sambucinum and F. fujikuroi were restricted to Ahwaz, Zanjan and Rasht, respectively. Furthermore, soil solarisation treatments were applied to F. pseudograminearum, F. solani and F. oxysporum, as the main cause of root rot pathogens and wilt disease of wheat, bean and date palm, respectively. After 6 weeks of soil solarisation application, the population densities of these species were decreased from 900 to 100 CFU g?1 in F. solani, from 600 to 50 CFU g?1 in F. oxysporum and from 550 to 0 CFU g?1 in F. pseudograminearum showing a promising result in controlling soil-borne pathogens. Mycogeography of Fusarium species and the effect of soil solarisation can help improve the management control strategies of these soil-borne fungi.  相似文献   

14.
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15.
Root rots (RR) are the main cause of declining bean (Phaseolus vulgaris) production in southwestern Uganda. Here, beans are mainly intercropped/rotated with maize (Zea mays), sorghum (Sorghum bicolor), sweet potato (Ipomoea batatas), potatoes (Solanum tuberosum) and garden peas (Pisum sativum). These crops also suffer from RR and bean RR pathogens have been isolated from some of these crops. This study aimed to determine the extent of RR on maize, sorghum and peas, and their potential to contribute to the survival of bean RR pathogens. Therefore, experiments were carried out in bean RR‐infested farmers’ fields as well as soils inoculated with bean RR pathogens (Pythium spp. and Fusarium spp.) under screen house conditions and a susceptible bean cultivar served as a control. High RR incidence/severity scores were recorded in beans and sorghum in both farmers’ fields and screen house experiments. The high field RR incidence/severity in sorghum correlated with the screen house scores. This study shows that RR is also a problem to other crops, especially sorghum, warranting attention. The findings also imply that sorghum plays a potential role as an alternate host to bean RR pathogens, increasing inoculum density of bean RR pathogens and potentially negatively impacting the bean RR problem. Intercropping or rotating beans with sorghum in this region is not recommended. However, maize was RR‐resistant and therefore appropriate as an intercrop/rotational crop to beans in the system. A holistic rather than commodity approach is recommended for managing RR in this cropping system.  相似文献   

16.
The area of protected crops in Hungary is about 5300 ha. Most of it is under plastic, the area under glass being only about 250 ha. Vegetable growing makes up 80%, mostly on private farms. The main crops are capsicum, tomato and cucumber. On relatively small areas, ornamentals, principally cut flowers, are produced: carnation, gerbera, rose and chrysanthemum. The three most important, commonly occurring pests are Trialeurodes vaporariorum, Tetranychus urticae and aphids (Aphis gossypii, Myzus persicae, A. nasturtii). Polyphagotarsonemus latus, Liriomyza trifolii and Aculops lycopersici caused considerable economic damage during the eighties. However, in the last few years these pests have not been observed in any crops. Two new glasshouse pests have been described from ornamentals during the last 2 years in Hungary: Frankliniella occidentalis and Bemisia tabaci. Their accidental appearance in vegetable crops could lead to direct economic loss, besides endangering biological control systems.  相似文献   

17.
Abstract

Many countries in the Arabian Peninsular are anxious to develop fully their limited agricultural resources. A knowledge of plant diseases and nematodes which attack their crops is essential before this is achieved. A survey of these in The Sultanate of Oman shows that soil-borne pathogens predominate and that the damage they cause is exacerbated by soil conditions. Nevertheless, some important pathogens are absent and hopefully their introduction to the relatively new agricultural areas in this part of the world can be prevented.  相似文献   

18.
Cover crops can suppress weeds within agricultural fields due to competitive and allelopathic effects. Glasshouse experiments were conducted to evaluate the relative proportions of allelopathic effects to the total weed inhibition. Six different cover crop species were combined with three weed species in the presence or absence of active carbon over a period of four weeks. Active carbon was used as an adsorbent for allelopathic substances in the soil. Our study revealed that the competition between cover crops and weeds shifted, possibly due to the minimisation of allelopathic effects by active carbon in the soil. We assume that the degree of cover crops allelopathic effects on weeds is species‐specific, both on the side of cover crops and on the weed side. The cover crops Raphanus sativus, Fagopyrum esculentum and Avena strigosa showed the highest allelopathic weed suppression with up to 28%. Additionally, Stellaria media turned out to be the most sensitive weed against allelopathic effects induced by all cover crops, except for Linum usitatissimum and Guizotia abyssinica. The knowledge about the contribution of competitive and allelopathic effects by cover crops would help to create cover crop mixtures with high weed suppressive ability.  相似文献   

19.
The area of land under protected cropping in the sub-tropical region is surveyed. In the northern part of the region, glasshouses are prevalent, while in the southern part, plastic houses are more common. Integrated Pest Management (IPM) strategies under the different cultural and climatic conditions are presented, with special emphasis on the use of alternative control measures. The most important soil-borne and foliar diseases of vegetable and ornamental crops grown in the area are considered with respect to the most effective and widely used control methods. Use of resistant varieties and appropriate cultural practices is one of the control measures most frequently adopted. Particularly, control of environmental conditions can strongly decrease the severity of some foliar pathogens. In the case of soil-borne diseases, soil solarization is already carried out in practice. Antagonists, isolated from suppressive soils, can be used successfully against some plant pathogens and, in the future, could provide another option.  相似文献   

20.
Due to the need to diminish the amount of pesticides used, alternative ways of controlling fungal diseases have to be developed. Foliar diseases have been managed mainly by chemicals, but research has been started to develop integrated control programmes. Data from studies on epidemiology, in combination with nutritional and climatic management and use of partial resistant cultivars will lead to a reduced use of chemicals. Models used are: Botrytis cinerea in gerbera and roses, and powdery mildew in roses and cucumbers. Research has been intensified on biological control of these pathogens. In closed systems, with recirculation of the nutrient solution, soil-borne fungi can cause serious problems. Not only do diseases known from traditional cultural systems, like fusarium wilt of carnation, fusarium crown and root rot of tomato and Phytophthora and Pythium spp. in several crops occur, but also new problems like a new Phytophthora sp. and Gnomonia sp. in roses and a Cylindrocladium sp. in Spathiphyllum spp. To prevent introduction of pathogens in recirculation systems, emphasis is put on developing an integrated disease management programme by using disease-free planting material, disease-free irrigation water, strict hygienic measures, resistant cultivars, methods of disinfecting the nutrient solution and biological control. Research over the last 5–6 years has revealed good prospects for biological control, especially in closed systems with a limited amount of substrate. Wilt in carnation, caused by Fusarium oxysporum f.sp. dianthi can be prevented effectively by adding a non-pathogenic isolate of F. oxysporum and/or Pseudomonas spp. There are indications that non-pathogenic isolates of F. oxysporum are also effective against wilt disease in other crops. An isolate of Trichoderma harzianum appears to be very effective against fusarium crown and root rot of tomato. More applications of this, and other, biocontrol agents seem possible. However, translation of the results of research to practical application and registration is still very difficult.  相似文献   

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