Baiting Technique Research Articles

A Qualitative Baiting Technique for Selective Isolation and DNA Diagnosis of Rhizoctonia spp,Causal AGents of Rice Sheat Diseeases,from Soil

A baiting technique was evolved for selective isolation and DNA diagnosis of causal agents of rice sheath diseases by Rhizoctonia spp. from artificially inoculated and naturally infested soils using eleven plant stem segments and selective medium containing benomyl and metalaxyl. Rice, mat rush and wheat stem segments soaked in metalaxyl at 50~tg/ml were successfully used to isolate R, solani AG 1, R. solani AG 2, R. oryzae, R. or~/zae-sativae and R, fumigate from artificially infested soils. Moreover, rice and wheat stem segments soused in metalaxyl at 1007tg/ml were successfully used to extract genomic DNA derived from all Rhizoctonia spp. Metalaxyl untreated stems were colonized in significantly higher numbers and contained in significantly higher concentration of DNA of these Rhizoctonia isolates than untreated stems. Untreated stems were also colonized isolates and extracted DNA derived from other common soil-inhabiting fungi.

Amycolatopsis keratiniphila sp. nov., a novel keratinolytic soil actinomycete from Kuwait.

A keratinolytic, nocardioform actinomycete, strain D2(T), was isolated from Kuwait marsh soil by the bait technique using animal wool. Strain D2(T) was an aerobic, Gram-positive organism that produced light-grey aerial mycelium but no specific spore chains. 16S rDNA sequence analyses and chemotaxonomic markers were consistent with the classification of strain D2(T) in the genus Amycolatopsis, i.e. it had meso-diaminopimelic acid in its peptidoglycan, arabinose and galactose as its diagnostic sugars, the polar lipids phosphatidylinositol, phosphatidylethanolamine, hydroxyphosphatidylethanolamine and diphosphatidylglycerol, menaquinone MK-9(H4) and an iso-/anteiso-branched fatty acid pattern combined with 10-methyl-branched and 2-hydroxy-branched fatty acids. Amycolatopsis japonica was the closest phylogenetic neighbour of strain D2(T), showing 99.4% 16S rDNA sequence similarity with the novel strain. A. japonica and strain D2(T) could be clearly separated from each other on the basis of their low DNA-DNA reassociation value (55.9%). These data, together with its distinct physiological traits, led to the conclusion that strain D2(T) represented a novel species within the genus Amycolatopsis, for which the name Amycolatopsis keratiniphila (type strain D2(T) = DSM 44409(T) = NRRL B24117(T)) is proposed.

Population dynamics of epiphytic mycoparasites of the genera Clonostachys and Fusarium for the biocontrol of black pod (Phytophthora palmivora) and moniliasis ( Moniliophthora roreri) on cocoa ( Theobroma cacao)

Mycoparasites collected from aerial parts of the cocoa plant (Theobroma cacao) have shown great promise in the control of black pod, caused by Phytophthora palmivora, and moniliasis, caused by Moniliophthora roreri. However, the ecology of epiphytic mycoparasites is still poorly understood although it has a direct bearing on applied biocontrol practices, ranging from the identification and isolation of promising biocontrol candidates to formulation needs and required application frequency. One objective of this study was to determine the natural abundance of mycoparasites on cocoa flowers and pods in relation to crop development stage and cultivar. For this purpose, native mycoparasites were detected on cocoa flowers and pods using the precolonised plate baiting technique. Furthermore, the survival of an applied Clonostachys rosea isolate on cocoa pods on shaded and non-shaded trees was compared as well as the recolonisation patterns of surface-sterilised pods by native mycoparasites under these conditions. Clonostachys spp. were the most commonly isolated native mycoparasites, followed by Fusarium spp. No differences in the occurrence of native, epiphytic mycoparasites were observed between the three main cocoa cultivars, 'Criollo', 'Forastero' and 'Trinitario', nor between clones within these groups. Thus, a single biocontrol inoculum can be suitable for application to cultivar mixtures of cocoa commonly grown together in a field. Different susceptibility classes of segregating F1 populations of hybrids with resistance against M. roreri and P. palmivora supported similar population levels and taxonomic assemblages of mycoparasites. Therefore, we reject the hypothesis that these antagonists mediate resistance. Mycoparasite abundance and genetic disease resistance to black pod and moniliasis are independent phenomena and should lead to additive effects if employed simultaneously in an integrated disease management programme. The survival of applied C. rosea was not affected by the shading regime or any other meteorological parameter measured. On the other hand, recolonisation of surface-sterilised cocoa pods by most native mycoparasites was faster in the shade. Only Trichoderma spp. colonised pods exposed to direct sunlight faster than shaded ones. The implications for the design of biocontrol inocula and formulation technology are discussed.

Evaluation of mycoparasites as biocontrol agents of Rosellinia root rot in cocoa

Abstract Rosellinia spp. cause substantial mortality of cocoa (Theobroma cacao), especially in acidic soils rich in organic matter (O.M.) and, reportedly, low available phosphate. Cultural and chemical control are relatively ineffective and a supplementary biocontrol strategy would be highly desirable. Our aim was the isolation and evaluation of promising mycoparasites against Rosellinia of cocoa. We isolated 45 mycoparasites using a baiting technique. Three of them and a commercial isolate were prioritized for further evaluation based on their broad hostrange and/or effectiveness in pot bioassays. Because Rosellinia is favored by the same soil factors as mycoparasites, we investigated the effect of soil pH (range 4–6), O.M. (6–12%), and phosphate (0– 1000 mg kg −1 ) on their interaction. In vitro, both pathogens and antagonists grew well on a wide range of phosphate (0– 9500 mg kg −1 ) and at various pH (3.0–10.0) levels. The pH optimum usually coincided with the soil of origin and the phosphate optimum depended on the phosphate source used. In pot bioassays using natural soils, mixtures of antagonists exhibited more control than single strains and mixtures were effective over a wider range of soil conditions. High O.M. favored the pathogen more than its biocontrol agents. Soil pH interacted with the treatments such that biocontrol was most efficient at higher pH values and with the highest mixtures of antagonists. The addition of phosphate enhanced plant growth but had little effect on biocontrol efficacy. We conclude that mixtures of mycoparasites should be field tested in combination with liming and removal of O.M.

Improved methods of isolation and purification of myxobacteria and development of fruiting body formation of two strains

By using baiting techniques and different purification methods, a high number of myxobacterial strains have been isolated as pure cultures from soil of different regions of China. Because myxobacterial cells do not disperse easily in liquid media, a medium containing an enzymatic hydrolysate of casein (CEH) medium have been used for purification and purity tests combined in a single step. The key method, in which isolates are reintroduced to sterile rabbit dung to induce fruiting bodies formation, facilitates purification of myxobacteria. Sterile rabbit dung pellets are used to mimic the natural growth substance of these organisms which has the advantage that characteristic fruiting bodies emerge, which is a key characteristics in the taxonomy of myxobacteria. In this study, the optimum program of isolation and purification of some myxobacteria strains has been established which will facilitate screening programs. Moreover, the development of fruiting body formation of strain BD20 ( Chondromyces) and strain BD54 ( Cystobacter) have been recorded in this study.

Encapsulamento de Trichoderma inhamatum para o controle biológico de Rhizoctonia solani na propagação clonal de Eucalyptus

Testou-se um novo sistema para o encapsulamento de Trichoderma inhamatum em grânulos de alginato de sódio, visando o controle biológico de Rhizoctonia solani, agente etiológico da mela de estacas/miniestacas de Eucalyptus spp. para enraizamento. No novo sistema idealizado, foi utilizado um aparato simples capaz de substituir eficientemente o equipamento (Bomba Peristáltica) anteriormente utilizado, sendo possível aumentar a produção de 594 grânulos/min para aproximadamente 6.734 grânulos/min. Com este novo sistema, um isolado de T. inhamatum (UFV – 03) foi encapsulado em grânulos contendo as fontes alimentares: farelo de trigo, palha de arroz, farelo de aveia, folhas de eucalipto ou farelo de milho na concentração de 50 g/l. Na segunda etapa, a melhor fonte alimentar foi testada nas concentrações de 0 a 60 g/l. Os grânulos foram veiculados em substrato de enraizamento de eucalipto na concentração de 2% (p/p) inoculado com micélio triturado de R. solani (2 mg/g de substrato) e a atividade saprofítica do patógeno foi quantificada por meio do método de iscas. Posteriormente, os grânulos produzidos com a fonte alimentar e concentração que promoveram maior inibição do desenvolvimento de R. solani foram utilizados para determinar o tempo mínimo de pré-incubação e competição para supressão do patógeno, com a mesma metodologia. Observou-se aumento da supressão da atividade saprofítica de R. solani ao acréscimo de uma fonte alimentar. Daquelas testadas, farelo de trigo foi a melhor. Além disso, houve interação significativa e positiva ao aumento de sua concentração na formulação.

Ecology of dermatophytes and other keratinophilic fungi in swimming pools and polluted and unpolluted streams.

The biodiversity and richness of keratinophilic fungal communities including dermatophytes were assessed in three stream sites and three swimming pools in the Nablus district in Palestine, using hair baiting (HBT) and surface dilution plate (SDP) techniques, over 8- and 6-month periods, respectively. The effect of wastewater effluent and selected ecological factors on these fungi in relation to species diversity and population densities were also considered. Fifty keratinophilic fungal species were recovered from the aquatic habitats studied, of which 42 were recovered from stream sites and 22 from swimming pools. Of these fungi 6 were either dermatophytes (Microsporum gypseum, and Trichophyton mentagrophytes) or dermatophyte related species (Chrysosporium merdarium, Ch. tropicum, Ch. keratinophilum and T. terrestre). The most frequently isolated species in the three pools were Acremonium strictum and Cladosporium cladosporioides, using Sabouraud dextrose agar medium (SDA). The most abundant species were Acr. strictum, and Aspergillus flavus. However, only 4 species were isolated using the SDA medium amended with 5-flurocytosine (5-FC). The most frequent and abundant species in the three stream sites using SDA medium were Geotricum candidum, and Penicillium chrysogenum. The most frequent species in the three sites using the 5-FC medium, was Paecilomyces lilacinus. Using HBT, the most abundant and frequent species in the three stream sites were G. candidum, and Pa. lilacinus, on SDA medium, and Pa. lilacinus, and Gliocladium nigrovirens on the 5-FC medium. The 5-FC medium was more suitable for the isolation of dermatophytes and closely related species than the SDA medium; 6 were recovered on 5-FC, whereas only one on the SDA medium. Variation in the levels of keratinophilic fungal populations from the three stream sites sampled 5 times over an 8-month period, followed comparable fluctuation patterns. Wastewater affected fungal population densities with the highest levels in the un-polluted stream sites, and lowest in the heavily polluted sites. Swimming pools, polluted and un-polluted stream sites were found to be rich in pathogenic and potentially pathogenic fungi.

Investigation of alternative baits for rabbit control, and the examination of the distribution and longevity of 1080 in One-shot oats

The use of 1080-poisoned oats in rabbit-control programs has become less effective in some areas of Australia. Consequently, factors likely to influence the effectiveness of this bait, and alternative grain products for rabbit control, were investigated. Vacuum impregnation rates with 1080 (sodium monofluoroacetate) for malted and unmalted barley were such that all barley products tested could be used as bait material in conventional rabbit-control programs where individual grains need to contain ~0.02–0.04 mg of 1080. In contrast, only the impregnation rates for malted barley (3.2 mg per grain) showed sufficient promise that this product could be considered for further development for use in 'One-shot' rabbit-control programs (poison grains nominally need to contain 4.5 mg 1080). Compared with oats, non-toxic malted and unmalted barley were equally acceptable food items to free-ranging rabbits. The addition of salt (NaCl, 0.9%) did not enhance the consumption of bait (oats and malted barley).1080 was not uniformly distributed throughout the poisoned One-shot oats, with 80% of the active ingredient in the husk, and 20% in the kernel. The size of oat also influenced impregnation rates, with the larger grains containing more 1080. Dehusking of the oats by rabbits (i.e. only the kernel was consumed) occurred in ~84% of cases examined (n = 31 food stations). As little as 6 mm of rainfall resulted in the total loss of detectable amounts of 1080 in One-shot oats collected over 41 days from a standard bait trail laid on sandy soil during summer. The impact of the above on rabbit-control programs could be potentially overcome (partially or wholly) by: the development and inclusion of barley products as bait, the alternation of conventional and One-shot baiting techniques in control programs, the responsible inclusion of a chronic poison (e.g. anticoagulant, pindone) in baiting programs, and ensuring that all poison grains in any bait are of uniform size and contain as close as possible to the nominal amount of active ingredient.

Occurrence and Identification of Phytophthora spp. Pathogenic to Pear Fruit in Irrigation Water in the Wenatchee River Valley of Washington State

ABSTRACT Seven hundred forty-nine isolates of Phytophthora spp. were obtained from irrigation canals in eastern Washington State during the 1992 to 1995 and 1999 growing seasons. Isolates were retrieved using pear baiting techniques. All isolates were pathogenic to pear and were present in irrigation water beginning early in fruit development. Over the course of the 5 year study, 10 and 5% of isolates were identified as P. cactorum and P. citricola, respectively, using morphological criteria. The remaining isolates could not be identified using morphological criteria. Colony morphology of these isolates was characterized during all years of the study. In 1999, more detailed studies utilizing polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis of entire internal transcribed spacer (ITS) regions (ITS1, 5.8S, and ITS2) of ribosomal DNA for 180 isolates, and sequence analysis of ITS2 for 50 isolates, were used to investigate genetic variation and phylogenetic relationships among isolates. Isolates were divided into 12 groups based on their growth type on corn meal agar. Restriction digestion of the entire ITS region with three enzymes revealed 11 restriction digestion patterns among 180 isolates. PCR-RFLP and sequence data were obtained for 12 reference Phytophthora spp. (two species in each of Waterhouse's six morphological groups). Phylogenetic analysis of ITS2 regions revealed nine clades, each with strong bootstrap support. Molecular analyses revealed 23 isolates that were in the P. gonapodyides clade, 9 in the P. parasitica clade, 1 in the P. cactorum clade, 7 in the P. citricola/capsici clade, and 4 in the P. cambivora/pseudotsugae clade. The three isolates comprising clade 5 were significantly distinct from all other Phytophthora spp. in the databases and may represent a new Phytophthora sp. Colony morphology was not consistently correlated to PCR-RFLP pattern or ITS2 phylogeny, suggesting that the former criterion is insufficient for species identification. The results of this study indicate that at least nine phylogenetically distinct taxa of Phytophthora pathogenic to pear are present in irrigation water in North Central Washington.

Chytridiomycota e Oomycota da Represa do Guarapiranga, São Paulo, SP

Quinze táxons de Chytridiomycota e 18 de Oomycota foram isolados de amostras de água e solo na Represa do Guarapiranga, por meio de técnica de iscagem, com substratos celulósicos, queratinosos e quitinosos. Dos táxons de Chytridiomycota isolados, um pertence aos Blastocladiales, onze aos Chytridiales e três aos Spizellomycetales. Dos táxons de Oomycota, treze pertencem aos Saprolegniales e cinco aos Peronosporales. Septochytrium marilandicum Karling é citada pela primeira vez para o Brasil.

Distribution of Phytophthora cinnamomi in the northern jarrah (Eucalyptus marginata) forest of Western Australia in relation to dieback age and topography

The spatial distribution of Phytophthora cinnamomi Rands at seven dieback sites in the jarrah (Eucalyptus marginata Donn. ex Smith) forest of Western Australia was determined by the following two baiting techniques: in situ baiting with live Banksia grandis Willd. seedlings and ex situ baiting of sampled soil and root material. Four areas within each site were sampled, reflecting dieback age and position in the landscape. Approximate dieback ages of 50, 20 and 5 years were determined by aerial photography. The 50-year-old age class was divided into wet valley floor and dry gravelly slope. Phytophthora cinnamomi was recovered most frequently from the 5-year-old (dieback fronts) and wet 50-year-old areas by both baiting techniques. It was recovered from more than twice as many areas and about five times as many samples when in situ B. grandis baits were used compared with ex situ soil and root baiting. Almost all recoveries from in situ baits were made between October and December. From both methods, it appears that P. cinnamomi has a patchy distribution within dieback sites in the northern jarrah forest. It is easily detected only on dieback fronts and wet valley floors. On dry gravelly sites affected 20 years or more ago, P. cinnamomi is rare and may even be absent at some sites. This makes confident detection of the pathogen difficult. In situ baiting at least allows a temporal component to the sampling and will be a useful method of detection in areas where P. cinnamomi is rare or transient.

Biocontrol of Cocoa Pod Diseases with Mycoparasite Mixtures

Abstract Five native mycoparasitic strains of Clonostachys rosea and three of Trichoderma spp. were isolated from healthy cocoa tissue or basidiocarps of Crinipellis perniciosa using a baiting technique. They were compared singly or in combination with the commercial biocontrol agent Trichoderma virens (SoilGuard) for their potential to control three cocoa pod diseases: moniliasis, caused by Moniliophthora roreri; witches' broom, caused by C. perniciosa; and black pod, caused by Phytophthora palmivora. All isolates except Trichoderma T-1 inhibited basidiocarp formation of C. perniciosa under controlled conditions. The remaining isolates except Trichoderma T-3 reduced vegetative broom formation in a seedling bioassay. Clonostachys rosea G-3 and Trichoderma strains T-2 and T-3 significantly reduced symptoms caused by M. roreri in a seedling bioassay. Host-range studies identified P. palmivora as most susceptible to mycoparasitism and M. roreri as most resistant; C. perniciosa was intermediate. Different degrees of susceptibility were discovered at the pathogen strain level, especially for P. palmivora. However, broad host-range mycoparasites which attacked all three pathogen species were identified. Under field conditions, all selected treatments except a combination of C. rosea G-2 + G-3 reduced moniliasis, the main disease, significantly by 14.6–24.9% as compared with optimized, cultural control alone. No significant reduction of witches' broom or black pod was achieved but a combination of five C. rosea strains (G-1, G-2, G-3, G-4 + G-5) performed consistently best against all three diseases simultaneously. Yield increased by 16.7% and net returns by 24%. Control of moniliasis and yield were positively correlated to the number of mycoparasites in the inoculum. The results suggest that simultaneous biocontrol of the three major cocoa pod diseases with mycoparasite mixtures is highly promising. Future development strategies are discussed.

Flebotomíneos da floresta de terra firme da Amazônia Peruana (Diptera: Psychodidae)

Um total de 1030 flebotomíneos, pertencentes a 14 espécies, foram coletados com armadilha tipo Shannon e isca humana, nos meses de Julho e Agosto de 1991, nos horários das 18:00 h. às 21:00 h., nas localidades de San Juan, San Pedro e 25 de Diciembre localizadas na Amazônia Peruana. As fêmeas foram mais abundantes do que os machos (96,98% e 3,02% respectivamente). Os subgêneros Psychodopygus (49,27% e 7 spp. coletadas) e Nyssomyia (48,79% e 4 spp. coletadas) comportaram o maior número de espécies e indivíduos. As espécies Lutzomyia richardwardi (48,4%) e L. carrerai (29,2%) foram as mais abundantes. Na localidade de San Juan foi coletado o maior número de indivíduos (55,2%), porém o maior número de espécies foi obtido na localidade de 25 de Diciembre. Quanto a estratégia de coleta, o mesmo número de espécies (12 spp.) foram obtidos com ambas as armadilhas, porém um maior número de indivíduos foi capturado com a técnica de isca humana.

A combination of baiting and PCR techniques for the detection of Phytophthora quercina and P. citricola in soil samples from oak stands

A description is given of the use of a combination of polymerase chain reaction (PCR) and baiting techniques for the specific detection of Phytophthora quercina and Phytophthora citricola from soil around declining oak trees. The soil was flooded with water and subjected to a specific baiting procedure using Quercus robur leaflets as baits. Single round or nested PCR, respectively, with species‐specific primers allowed the detection of P. quercina and P. citricola in infected oak leaflets used as baits and in the water from the same bait tests. PCR detection of both fungi was also possible after soil samples had been thoroughly mixed with water and the floating organic debris had been collected. Phytophthora quercina and P. citricola could be readily detected in almost every case in the water from these tests by PCR but less frequently in the organic debris. The identities of P. quercina and P. citricola were confirmed by restriction digests of the corresponding PCR amplicons. The presence of both fungi was also confirmed in parallel in soil samples tested by baiting with oak leaflets. Nested PCR with the primers used allowed the detection of as few as five zoospores of P. citricola and 300 zoospores of P. quercina in a volume of 100 μl. The methods presented here allow detection and identification of species of Phytophthora in soil without the need for direct extraction of soil samples, and without specific knowledge of the morphological characteristics of the genus.

Bait-delivered cabergoline for the reproductive control of the red fox (Vulpes vulpes): estimating mammalian non-target risk in south-eastern Australia.

Cabergoline (CAB) is a potent dopamine agonist and an inhibitor of prolactin (PRL). In red foxes (Vulpes vulpes), a single oral dose of 100 microg kg(-1) CAB can cause abortions and postnatal cub mortality from at least Day 21 of the 52-day pregnancy. The abortifacient activity of CAB is owing to the suppression of PRL, which is essential for luteotrophic support in some eutherian species. Postnatal cub mortality probably results from a reduction in the development of the mammary ductile system, which is also partially dependant on PRL during pregnancy. This paper investigates the potential risks faced by non-target mammalian species that may consume CAB baits intended for fox control. Baiting with CAB is proposed from 1 August until 1 October each year, to correspond with the time that most vixens are pregnant in south-eastern Australia. Thirty-four endemic mammals in south-eastern Australia (9 eutherians and 25 marsupials) are considered to be potentially bait-consuming (PBC) species. The percentage overlap of pregnancy and birth periods for each PBC species was compared with the duration of the proposed CAB baiting period. Only Antechinus (3 species) and Sminthopsis leucopus have greater than 40% overlap, whereas overlap in endemic rodents ranges from 0% to 22%. Overall, most PBC rodent populations appear to face little risk from CAB baiting, as their period of pregnancy does not overlap significantly with the proposed CAB baiting period. The Antechinus species, Phascogale tapoatafa and Dasyurus maculatus, are the only PBC mammals that are seasonally mono-oestrous and are thus probably more susceptible to disruption of breeding compared with polyoestrous species that may breed many times a year. At a baiting density of 8 baits km(-2), theoretical bait availability for small dasyurids, rodents and peramelids is low. This suggests a low potential for affecting these populations if CAB was indiscriminate in affecting reproductive success in all mammal groups. Presently, studies in a limited range of marsupials suggest that, unlike eutherians, the marsupial corpus luteum is independent of pituitary control and thus suppression of PRL is not likely to cause abortions in marsupials. As yet, CAB has not been shown to be orally active in any PBC species other than rodents and carnivores. Oral doses of CAB given post partum have not been found to affect lactation in Sminthopsis crassicaudata, Trichosurus vulpecula, Macropus eugenii and Setonix brachyurus. Further studies are required in order to assess the potential for high doses of oral CAB to affect pre-partum mammary development and early lactation post partum, especially in peramelids and larger dasyurids. Highly target-specific baiting techniques, may eliminate most PBC species from being exposed to CAB and these are briefly discussed.

Organic amendment of commercial culture media for improving control of Rhizoctonia damping-off of cabbage

Rhizoctonia solani AG-4 is an important damping-off pathogen of cabbage. Using a baiting technique, R. solani was recovered from the cabbage seeds buried in nine commercial culture media. The frequency of seed colonization by R. solani varied with medium, ranging from 2.5% in Nev-3 to 30% in Floradur A and SI 2; the seeds were examined after being buried for 48 h. Among the five formulated organic compounds tested as amendment for the commercial BVB No. 4 medium, FBN-5A was most effective in controlling damping-off. Although both rates of FBN- 5A, 0.1% and 0.2%, significantly reduced incidence of damping-off, FBN-5A at 0.1% was the more suitable treatment because it not only reduced the disease incidence, but also enhanced the growth of cabbage. The results were confirmed in a large-scale experiment in a commercial automatic environment-controlled greenhouse. This study suggests that the FBN-5A compound offers potential for commercial use as an organic amendment for the management of Rhizoctonia damping-off of vegetable crops.

Phytophthora Species Associated with Cranberry Root Rot and Surface Irrigation Water in New Jersey.

A lupine baiting technique was used to detect the presence of Phytophthora spp. in several streams, irrigation reservoirs, and drainage canals used in cranberry cultivation. P. cinnamomi was found to be widely distributed throughout the study area in the southern New Jersey Pinelands, and was present both upstream and downstream of agricultural activities. A second species, identified as P. megasperma, was more restricted in its distribution and was never isolated from a water system that did not also contain P. cinnamomi. In a survey of commercial cranberry production, 80% of the acreage represented (approximately 37% of total New Jersey production area) was exposed to one or both Phytophthora spp. through application of infested water from irrigation reservoirs. Based on the widespread distribution of P. cinnamomi, it is likely that this pathogen was introduced many years prior to its discovery on cranberry in the 1980s, which corresponded to the adoption of overhead irrigation in the crop. There were slight differences between the two species in seasonal occurrence. The highest levels of P. cinnamomi were found during the summer months (July to August) whereas P. megasperma was highest during the spring (April to May) and fall (September to October) months.

Isolation of Pythium acanthicum, P. oligandrum, and P. periplocum from soil and evaluation of their mycoparasitic activity and biocontrol efficacy against selected phytopathogenic Pythium species

Mycoparasitic Pythium species with spiny oogonia were surveyed in 50 Palestinian agricultural fields subject to different cropping practices using the Sclerotia Bait Technique (SBT) and the Surface-Soil-Dilution-Plate method (SSDP) with the selective VP3 medium. The mycoparasitic Pythium species were obtained from 21 (42%) soils using the SSDP method and from 37 (74%) soils using SBT. Pythium acanthicum and P. oligandrum were isolated by both methods, whereas P. periplocum was isolated only by the SBT. Using a newly modified dual plate culture method (MDPCM), the three mycoparasites showed varying antagonistic performance against several Pythium host species under a range of in vitro conditions. However, P. periplocum and P. oligandrum were found to be active biocontrol agents against P. ultimum, the damping-off organism of cucumber. This pathogen was antagonized, on thin films of water agar, by the three mycoparasites, and was moderately susceptible to P. periplocum while slightly susceptible to P. acanthicum and P. oligandrum. In direct application method in which antagonistic mycoparasites were incorporated into peat/sand mixture artificially infested with P. ultimum under growthroom conditions, Pythium oligandrum and P. periplocum (at 500 CFUg−1) significantly improved seedling emergence and protected seedlings from damping-off. In the seed coating method, biocontrol by two types of seed dressing (homogenate- or oospore coated seeds), was comparable to that achieved by direct application.

Fungal succession on leaves of Alchornea triplinervia (Spreng.) Muell. Arg. submerged in a stream of an Atlantic Rainforest in the state of São Paulo, Brazil

Leaves of Alchornea triplinervia (Spreng.) Muell. Arg. were submerged in a stream in an Atlantic Rainforest in Sao Paulo state, Brazil, from July/1988 to June/1989 and from July/1989 to May/1990. Fungi were isolated by the leaf disks washing technique followed by plating on culture media and also by using baiting techniques (using substrates with chitin, keratin and cellulose), what resulted on 565 fungal registers corresponding to 81 taxa. The most common species found during this study of the fungal succession were Trichoderma viride Pers. ex S.F. Gray and Fusarium oxysporum Schlecht emend. Snyd. & Hans. (23 registers), Penicillium hirsutum Dierckx (21 registers), Fusarium solani (Mart.) Appel & Wollenw. emend. Snyd. & Hans. (17), followed by 14 registers of: Cylindrocladium scoparium Morgan, Triscelophorus monosporus Ingold and Polychytrium aggregatum Ajello. Although the monthly obtained mycota had been composed by species of different taxonomic groups, the fungal succession was defined by the initial presence of typical terrestrial leaf inhabiting fungi (mostly Deuteromycotina), followed by species of Mastigomycotina and Zygomycotina. Combining culture methods and baiting techniques, it was possible to verify the presence of terrestrial fungi on the decomposition of submerged leaves and the importance of zoosporic fungi in the fungal succession. This is the first paper about the fungal succession on the decomposition of leaves submerged in a lotic ecosystem in Brazil.

Dark septate hyphomycetes in swiss conifer forest soils surveyed using Norway-spruce seedlings as bait

Soil samples were collected under Norway-spruce trees ( Picea abies (L.) Karst.) on 72 sites throughout Switzerland, passed through a disinfected sieve and put into autoclaved clay pots. Surface-sterilized Norway-spruce seeds were sown into these pots and the seedlings were reared in a growth cabinet for 4 months. The root systems of nine seedlings per site were surface-sterilized and one 2–3 mm long segment of each of two root-diameter classes (class 1: dia <1 mm, class 2: dia 1–2 mm) was aseptically excised from each root system and plated out on 2% (w/v) malt-extract agar to isolate fungi. Dark septate hyphomycetes (DSH) could be isolated from the soil samples of all except two sites. The frequency of seedling roots colonized by DSH ranged from 11–100%, the average being 76%. Colonization of root diameter class 2 was significantly higher than the one of class 1. No site-dependent pattern of colonization could be recognized except for the soil pH value. The frequency of DSH was correlated with the pH value of the collection sites and reached the maximum between pH values 3.5 and 4.5. The health status of the seedlings as measured by needle color, presence or absence of needle tip chlorosis, the number of living seedlings per pot and the dry weight was not correlated with the colonization of the roots by DSH. About 49% of the DSH sporulating after 1 y of incubation at 4°C in the dark were identified as Phialocephala fortinii. Advantages and disadvantages of the baiting technique are discussed.