Elucidation of factors contributing to onset of Cercospora leaf blight during later reproductive development of soybean

In Louisiana, Cercospora leaf blight (CLB) of soybean is primarily caused by Cercospora cf. flagellaris, which can be detected in asymptomatic leaves as early as V3 (third trifoliate) growth stage, while symptoms appear around R5 (beginning seed). The fungus produces cercosporin, an important virulence factor, the in vitro production of which is significantly reduced in the absence of simple sugars. Our objective was to investigate the role of foliar simple sugars and endophytic bacteria in CLB symptom onset. C. cf. flagellaris was cultured in filter-sterilized, untreated extracts made from asymptomatic R2 and R5 leaves; in extracts treated with chloroform to isolate hydrophilic molecules, including simple sugars; or with antibiotics to assess the role of endophytic bacteria. Endophytic bacteria were also isolated from leaves and leaf extracts and their interaction with C. cf. flagellaris was investigated. The fungus produced more cercosporin in total R5 and simple sugar-amended R2 leaf extracts, than in R2 leaf extracts. Furthermore, it produced more cercosporin in chloroform-treated R5 leaf extracts, which contained significantly higher levels of simple sugars, especially fructose, than the R2. To our knowledge, this is the first reported connection between foliar sugar content and cercosporin production. Additionally, morphologically diverse bacteria were isolated from different stages of soybean development. Also, bacterial endophytes in R5 leaf extracts and Paenibacillus polymyxa, isolated from R2 leaves, significantly reduced the growth of C. cf. flagellaris. These findings implicated soybean leaf fructose in CLB development and highlighted the potential of using foliar bacterial endophytes for CLB management.     

Genetic diversity of Phaeoisariopsis griseola in Argentina as revealed by pathogenic and molecular markers

Angular leaf spot, a disease of common bean produced by Phaeoisariopsis griseola, an imperfect (Deuteromycotina) fungus, causes significant yield losses in Argentina. The development of a strategy to control and/or reduce the impact of P. griseola requires a previous knowledge of the population structure. Therefore, the purpose of this work was to analyze diversity among 45 isolates of P. griseola collected within the production area of common bean in Northwestern Argentina. Pathotypes diversity was determined based on a set of bean differentials and genomic differences between isolates were determined by means of molecular markers. We confirmed that isolates belonging to Middle American and Andean groups coexist in Northwestern Argentina and the level of diversity between them was considerable and of similar level within each group. Even though the number of isolates analyzed was 45, among them 37 were Middle American and only eight were Andean. The number of haplotypes found based on ISSR and RAPD markers were 18 and as expected, they were unrelated with pathotypes. The wild bean species, Phaseolus vulgaris var. aborigineus, showed a high level of tolerance to most pathotypes of P. griseola except 63.63 and 63.23. This together with the fact that none of the bean differentials was resistant to all pathotypes led us to conclude that the range of pathogenic responses might be conditioned by multigenic interactions between the pathogen and the host. Our results not only provided basic information about the diversity of the causative agent of the disease but it will also help to develop cultivars with enhanced tolerance and/or resistance to the disease.     

Pseudocercospora griseola,the causal agent of common bean angular leaf spot: Strain characterization and sensitivity to fungicides

Angular leaf spot (ALS), an important disease of common bean (Phaseolus vulgaris), is caused by the fungus Pseudocercospora griseola. This pathogen has a wide genetic variability and, therefore, poses a challenge to integrated disease management. The use of resistant cultivars is difficult; hence, the application of fungicides has been a common practice in common bean cultivation. P. griseola strains were morphophysiologically characterized and their sensitivity to common fungicides used to control ALS was studied. The strains were evaluated for sporulation capacity and a representative sample of 34 strains was bioassayed to determine their sensitivity to commercial concentrations of five fungicides, namely pyraclostrobin, mancozeb, pyraclostrobin + metconazole, chlorothalonil and tebuconazole. Another sample of 29 strains was studied for conidial germination and dimensions. Sporulation capacity ranged from 0.88 to 27.67 × 10⁴ conidia/ml and germination percentage ranged from 39% to 72%. The large differences among strains suggest a wide genetic variability among the strains. A wide variability in aggressiveness of P. griseola was observed, which has consequences for breeding programmes aimed at resistance. The behaviour of pathogen strains differed in every fungicide evaluated, even in a population that has not been under selection pressure in the field. These results confirm the need for further studies and may guide future research with this pathogen.     

Epiphytic Curtobacterium flaccumfaciens strains isolated from symptomless solanaceous vegetables are pathogenic on leguminous but not on solanaceous plants

In Iran, during 2013–16, 16 Gram‐positive corynebacteria‐like strains were recovered from the epiphytic parts of solanaceous vegetables including eggplant, pepper and tomato. The strains were recovered accidentally as a result of monitoring for other bacterial pathogens in solanaceous fields. The strains were phenotypically different from Clavibacter michiganensis strains. Although none of the strains were pathogenic on their host of isolation or on any other solanaceous plants, 12 out of 16 strains were pathogenic on common bean, cowpea, mung bean and soybean. Colonization by strains was observed on maize, zucchini, faba bean, honeydew melon, rapeseed, sugar beet and sunflower plants under greenhouse conditions. In PCR tests, the primer pair CffFOR2/CffREV4, specific for Curtobacterium flaccumfaciens pv. flaccumfaciens, enabled the amplification of the appropriately sized fragment in 12 out of 16 strains, and all 12 strains were pathogenic on dry beans. Phylogenetic analysis, using the gyrB and recA genes, showed all 16 bacterial strains clustered within several pathovars of C. flaccumfaciens. A nonpathogenic yellow‐pigmented strain (Xeu15) was clustered with the type strains of C. flaccumfaciens pv. betae and C. flaccumfaciens pv. oortii. Bacteriocin profiling assays revealed no significant differences among the pathogenic and nonpathogenic strains. Host range and population dynamics of four representative strains on 17 plant species showed population build‐up of the strains only on common bean, cowpea, wheat and red nightshade plants. The results provide important insights into the possible role of nonhost plants as reservoirs of plant pathogenic bacteria, which has important implications in plant disease epidemiology and management.     

Relationships Between Angular Leaf Spot, Healthy Leaf Area, Effective Leaf Area and Yield of Phaseolus vulgaris

Three field experiments were carried out with the bean cultivar Carioca Comum to investigate the relationships among visual and virtual severity of angular leaf spot (caused by Phaeoisariopsis griseola), area under visual and virtual disease progress curves (AUDPC), healthy leaf area index on any given day (HLAI), healthy leaf area duration (HAD), healthy leaf area absorption (HAA), effective leaf area duration (ELAD), effective leaf area absorption (ELAA) and yield of Phaseolus vulgaris. To obtain a wide range of disease severities, the plots were sprayed with fungicide at different stages of plant growth (before, during and after flowering). Visual and virtual severity and AUDPC showed no significant correlation with yield. However, HAD, HAA, ELAD and ELAA were significantly correlated with yield. Variables that considered the effective leaf area (ELAD and ELAA) provided similar or better coefficients of determination (R²) than those that considered the remaining green leaf area only (HAD and HAA). Single-point models with HLAI, effective leaf area index (ELAI), intercepted radiation by healthy leaf area (HRI) and intercepted radiation by effective leaf area (EHRI) to estimate yield at various times during the crop season were developed. The slope of the relationship between yield and HLAI, ELAI, HRI and EHRI proved to be stable, regardless of planting date and bean growth stage (from R6 to R8).     

Identification of resistance to Cercospora leaf spot of cowpea

Twelve selected cowpea cultivars were screened for resistance to Cercospora leaf spot (CLS) disease caused by Pseudocercospora cruenta and Cercospora apii s. lat. under artificial epiphytotic conditions in a replicated field trial, with the objective of developing a quantitative measure of disease resistance. CLS incidence, leaf spotting score, lesion density, lesion size, proportion of nodes infected, diseased leaf area, conidia number mg⁻¹ and fascicle density were assessed in 12 cowpea genotypes at crop maturity. Proportion of nodes infected and leaf spotting score were best able to quantitatively differentiate between the levels of resistance, and allow the exploitation of quantitative resistance to the disease. Both lesion density and lesion size were important in determining the final leaf spotting score but the former was epidemiologically more important than the latter, indicated by its correlation to most of the CLS symptom measures. There was differential resistance to the P. cruenta and C. apii s. lat. among the cowpea varieties screened. Among the cowpea lines screened, resistance to P. cruenta was more common than resistance to C. apii s. lat. Nevertheless, P. cruenta was considered the more aggressive and epidemiologically more important than C. apii s. lat. on the varieties tested evidenced by the strong correlation of P. cruenta incidence with acropetal spread of CLS, intensity of leaf spotting, conidia number mg⁻¹ and fascicle density. The highly susceptible varieties namely VRB7, Los Banos Bush Sitao no.1 and CB27 were susceptible to both Cercospora pathogens. The cowpea variety VRB-10 was completely resistant to both pathogens and is a useful source of resistance in CLS breeding programmes.     

Colletotrichum species causing anthracnose on avocado fruit in Mexico: Current status

Colletotrichum species cause anthracnose disease in tropical and subtropical fruit crops worldwide. Mexico is the main producer and exporter of avocado (Persea americana) globally and has yearly outbreaks of anthracnose on this crop. However, which specific Colletotrichum spp. cause these outbreaks in avocado-producing regions remain uncertain; thus, the objective of the present study was to identify the species responsible. A survey performed in six production regions of Mexico yielded 232 isolates, from which a subset of 104 strains was selected based on morphological characteristics and origin. This subset was sequenced and haplotypes were analysed in the gapdh partial gene. Finally, 31 strains were identified through multilocus phylogenetic analyses using the sequences of the internal transcribed spacer region and six loci. This study revealed the presence of two species previously reported in Mexico (C. karsti and C. godetiae), three novel records in Mexico (C. siamense, C. fioriniae, and C. cigarro), four novel records on avocado (C. chrysophilum, C. jiangxiense, C. tropicale, and C. nymphaeae), and two novel lineages (Colletotrichum sp. 1 and Colletotrichum sp. 2). C. siamense was the most prevalent, while the species reported for the first time on avocado, including the novel lineages, were the least prevalent. C. karsti was the most widespread (four regions), followed by C. siamense, C. jiangxiense, and C. chrysophilum (three regions). Pathogenicity tests showed that all species caused anthracnose on avocado fruit. These findings will be useful for improving the management of avocado anthracnose outbreaks in Mexico.     

Diversity and occurrence of chickpea chlorotic dwarf virus on legumes from Iran

Chickpea chlorotic dwarf virus (CpCDV; genus Mastrevirus, family Geminiviridae) is one of the most important legume-infecting viruses with a wide host range and geographic distribution in Africa and Asia. In Iran, CpCDV is common in chickpea (Cicer arietinum), but there is limited information about diversity and infections in plants of other legume species. In the current study, a total of 1671 leaf samples from different pulse crops with symptoms were collected in nine provinces of Iran, and the CpCDV infection status was tested by PCR and/or rolling circle amplification (RCA), resulting in the detection of CpCDV in samples of chickpea, lentil (Lens culinaris) and faba bean (Vicia faba) from different regions. Sequence analysis of complete genomes of 18 isolates recovered by digestion of RCA products revealed infection with isolates of the strains CpCDV-A and CpCDV-F in chickpea, lentil and faba bean. Phylogenetic analysis showed that the Iranian isolates of CpCDV were closely related to previously sequenced isolates of CpCDV-A and CpCDV-F. To the authors' knowledge, this is the first report of CpCDV-F in Iran. Using agroinoculation with infectious clones for one isolate each of CpCDV-A and CpCDV-F, infectivity was confirmed in both faba bean and chickpea, with plants developing leaf curling and/or yellowing. Both infectious clones also successfully infected Nicotiana benthamiana resulting in mild yellowing and intensive leaf curling for CpCDV-A, and dark-green mosaic, dwarfing and mild leaf curling for CpCDV-F.     

Studies of canker and dieback of oak tree in China,with two Cytospora species described

Oak (Quercus sp.) is an excellent tree species as a windbreak, for water conservation, and for fireproofing in forests in China. However, several trees of this genus were found to be suffering from various fungal diseases. In this study, we evaluated 15 fungal pathogens that can cause dieback and canker disease in oak in China, and discovered two Cytospora species. They were identified as Cytospora quercinum sp. nov. and C. vinacea, based on detailed morphological comparisons and phylogenetic analysis of ITS, LSU, act, rpb2, tef1-α, and tub2 loci. This study is the first record of C. quercinum and C. vinacea as causal agents of dieback in oak based on pathogenicity tests conducted on 2-year-old plants in a greenhouse. In addition, this study also revealed the influence of different conditions on the growth rate of mycelia. Mycelial growth of C. quercinum and C. vinacea occurred at optimum temperatures of 20.1 and 20.8 °C, and optimum pH of 5.4 and 5.3, respectively. For these two species, utilization of glucose and fructose was highly efficient, and sucrose was the least efficient. The habitat of Quercus mongolica indicated that more attention and management are needed to prevent the occurrence of Cytospora disease in the summer in north-eastern China, and in spring and autumn in eastern and northern China. This study contributes to the understanding of the species causing canker or dieback diseases in important economic forest trees, and provides useful information for effective disease management of oak trees in China.     

Pathogenicity of Aphanomyces spp. from Different Leguminous Crops in Sweden

Host range and pathogenicity of a range of Aphanomyces spp. isolates obtained from pea roots but also from a range of other field-grown leguminous crops in southern Sweden was investigated. The Aphanomyces euteiches isolates originating from pea and the few obtained isolates originating from alfalfa, green bean and yellow sweet-clover were highly pathogenic only to pea. The A. euteiches isolated from common vetch differed from these isolates by being weakly pathogenic to pea and other legumes, but highly pathogenic to common vetch. Vetch isolates also formed a well-defined separate cluster based on principal component analysis of pathogenicity pattern on tested crops. Oospores of A. euteiches were observed in root tissue of pea as well as common vetch, alfalfa, green bean, broad bean, red clover and yellow sweet-clover in the greenhouse pathogenicity tests. An Aphanomyces sp. that morphologically differed from A. euteiches, was frequently isolated from several leguminous plants, but was non-pathogenic to all tested crops in the pathogenicity tests. In isozyme analysis the banding pattern of these isolates resembled the pattern of A. cladogamus. Another, different and so far unidentified Aphanomyces sp. from roots of green bean and broad bean, was also non-pathogenic to the tested legume species. Based on the isolates tested, the results obtained suggest that the population of Aphanomyces spp. infecting legume roots in Sweden consists of a pea-specific and a vetch-specific group of A. euteiches. Two other groups comprised (i) Aphanomyces sp. isolates that resembled A. cladogamus, and (ii) isolates, which resembled neither A. euteiches nor A. cladogamus. In addition, the host range of Swedish A. euteiches isolates was not as broad as reported for A. euteiches isolates from other countries.     

Characteristics and distribution of Colletotrichum species in coffee plantations in Hainan,China

Anthracnose caused by Colletotrichum species is a serious disease on a range of economically important hosts. To determine the Colletotrichum species in coffee plantations in Hainan, China, 55 isolates were obtained from Coffea arabica (arabica) and C. canephora var. robusta (robusta) in five counties. Initially, partial sequences of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were used to measure fungal genetic diversity. Then a subset of 23 isolates was selected to represent the range of genetic diversity, varieties and geographic origin for further multilocus phylogenetic analyses. These isolates belong to eight known Colletotrichum species from three Colletotrichum species complexes, including gloeosporioides (C. endophytica, C. fructicola, C. ledongense, C. siamense and C. tropicale), boninense (C. karstii), gigasporum (C. gigasporum), and one singleton species (C. brevisporum). Of these, C. siamense was isolated in all sampled counties and C. fructicola was identified in three counties. The other six species were isolated only in one or two counties. Only C. siamense and C. fructicola were isolated from arabica, whereas all eight species were isolated from robusta. Occurrence of C. brevisporum, C. endophytica, C. ledongense and C. tropicale in coffee has not been reported previously. Pathogenicity tests showed that all eight species were pathogenic to coffee leaves and fruit. In vitro tests showed that Colletotrichum isolates from coffee in Hainan were most sensitive to prochloraz, less sensitive to carbendazim, propiconazole and difenoconazole, and least sensitive to myclobutanil.     

我国玉米灰斑病菌遗传多样性的ISSR分析

为明确我国发生的玉米灰斑病菌地理差异及遗传结构,利用简单序列重复区间(ISSR)对玉米灰斑病菌遗传多样性进行了分析,并利用尾孢菌特异引物对分离自四川、云南、湖北、贵州等西南地区的16个玉米灰斑病菌菌株进行了分子鉴定。结果显示,通过ISSR标记筛选出10个扩增多态性好且稳定的通用引物,共扩增出81条DNA条带,均为多态性条带,扩增片段大小在200~2 000 bp之间,菌株遗传相似系数为0.19~1.00。在遗传相似系数为0.19时,供试菌株被聚为2大类群,来自西南地区和东北地区的菌株各自聚为一组,在DNA水平上表现出明显差异,认为是2类不同的致病类群。分子鉴定结果显示引起西南各地区玉米灰斑病的主要致病菌均为玉米尾孢菌Cercospora zeina。表明我国玉米灰斑病菌存在丰富的遗传多样性,ISSR标记可揭示出玉米灰斑病菌株间的亲缘关系及遗传差异性,可用于其遗传多样性研究。     

Characterization of Cytospora isolates from wood cankers of declining grapevine in North America,with the descriptions of two new Cytospora species

Cytospora species are ubiquitous pathogens of numerous woody plants, causing dieback and wood cankers in agronomic crops, timber trees and wildland trees (e.g. Prunus, Eucalyptus and Salix, respectively). Cytospora chrysosperma, C. cincta and C. leucostoma have been reported from grapevines in Iran showing symptoms of one or more recognized trunk diseases (esca, botryosphaeria‐, eutypa‐ and phomopsis diebacks); however, only C. chrysosperma was shown to be pathogenic to grapevine. To understand the potential role of Cytospora species in the grapevine trunk‐disease complex, 21 Cytospora isolates were examined that were recovered from dieback and wood cankers of Vitis vinifera and Vitis interspecific hybrids in seven northeastern U.S. states and two Canadian provinces. Phylogenetic analyses of ITS and translation elongation factor 1‐α identified two novel species: Cytospora vinacea sp. nov. and Cytospora viticola sp. nov. Differences in culture morphology and conidial dimensions also distinguished the species. When inoculated to the woody stems of potted V. vinifera ‘Thompson Seedless’ in the greenhouse, both species were pathogenic, based on development of wood lesions and fulfilment of Koch's postulates. Cytospora viticola was the most virulent based on lesion length at 12 months post‐inoculation. As cytospora canker shares some of the same general dieback‐type symptoms as botryosphaeria‐, eutypa‐ and phomopsis diebacks, it may be considered part of the grapevine trunk‐disease complex in eastern North America.     

Persistence of <Emphasis Type="Italic">Xanthomonas axonopodis</Emphasis> pv. <Emphasis Type="Italic">vignicola</Emphasis> in weeds and crop debris and identification of <Emphasis Type="Italic">Sphenostylis stenocarpa</Emphasis> as a potential new host

The survival of Xanthomonas axonopodis pv. vignicola, incitant of cowpea bacterial blight and pustule, in residues of infested cowpea leaves was studied in the field in the forest savanna transition zone of South Benin and under variable controlled conditions. The pathogen survived for up to 60 days when placed on the soil surface, and up to 45 days buried at depths of 10 and 20 cm. In the glasshouse, bacteria survived in residue mixed with soil for at least 2 months in dry soil and less than 2 months in moist soil. The pathogen survived at least 30 days in the field after spray-inoculation on the weed species Euphorbia heterophylla, Digitaria horizontalis and Synedrella nodiflora; 20 days on Panicum subalbidum; 10 days on Euphorbia hirta; and 5 days on Talinum triangulare. After leaf-infiltration under glasshouse conditions, the pathogen was detected after 90 days in D. horizontalis; 75 days in T. triangulare, P. subalbidum and S. nodiflora; 60 days in E. hirta, and 30 days in E. heterophylla. Among 12 legume species tested as alternative hosts of X. axonopodis pv. vignicola, only Sphenostylis stenocarpa (African yam bean) showed typical symptoms of cowpea bacterial blight in a glasshouse experiment following artificial inoculation. This is the first time this legume species has been identified as a potential host of X. axonopodis pv.vignicola. Crop residue and weeds are likely sources of primary inoculum when planting two consecutive cowpea crops per year and they probably play a role in dissemination of the pathogen during the cropping season. The alternate host may form a bridge for primary inoculum between cropping seasons.     

Parasitoids Associated with <Emphasis Type="Italic">Mussidia</Emphasis> spp. (Lepidoptera: Pyralidae) in Kenya

The pyralid Mussidia nigrivenella, a pest of cotton, maize and Phaseolus bean in West Africa, has never been reported as a crop pest in East and Southern Africa, although reportedly it exists in the wild. It is hypothesized that the difference in pest status of M. nigrivenella between western and eastern Africa was either due to differences in natural enemy compositions or that there exist several populations and/or species of Mussidia, which vary in their host plant range. Thus, a catalogue of parasitoids of Mussidia spp. was established through surveys in mid-altitude and coastal Kenya, between 2006 and 2007. Mussidia spp. eggs, larvae and pupae were collected from fruits of plants known to host Mussidia spp. and were examined for parasitoid-related mortality. The trichogrammatid Trichogrammatoidea sp. nr. lutea was obtained from eggs of Mussidia fiorii. A braconid egg-larval parasitoid, Phanerotoma sp., was reared from the larvae of unknown species of Mussidia (which we are referring to as Mussidia “madagascariensis”, Mussidia “quanzensis”) and M. fiorii, while the bethylid Goniozus sp. and the braconid Apanteles sp. were obtained from Mussidia nr. nigrivenella. Moreover, the ichneumonid larval parasitoid Syzeuctus sp. was obtained from M. fiorii, while the tachinid Leskia sp. was obtained from Mussidia “madagascariensis”. Overall, mortality caused by parasitoids was negligible; hence they were not considered key mortality factors in the population dynamics of the Mussidia spp. in Kenya.     

Factors influencing biological traits and aggressiveness of Colletotrichum species associated with cashew anthracnose in Brazil

Anthracnose is the main fungal disease on cashew orchards in Brazil, occurring on both vegetative and reproductive organs of cultivated and noncultivated host plants. Understanding the effect of physical and chemical exogenous factors on the biological traits of Colletotrichum spp. and determining their host range are key to developing appropriate anthracnose control measures. The present study aimed to estimate the optimum temperatures for mycelial growth, sporulation, and conidial germination of seven Colletotrichum species (C. chrysophilum, C. fragariae, C. fructicola, C. gloeosporioides, C. queenslandicum, C. siamense, and C. tropicale) associated with cashew anthracnose in Brazil. Their aggressiveness on cashew leaves and six alternative host fruits, and their sensitivity to three fungicides were also investigated. The optimum temperatures for mycelial growth, sporulation, and conidial germination ranged from about 25 to about 33°C. All Colletotrichum species induced anthracnose symptoms on wounded cashew leaves, but none of them caused lesions on intact leaf surfaces. The Colletotrichum species, except for C. fragariae and C. fructicola, were pathogenic to wounded fruits of avocado, banana, guava, mango, and papaya, and some isolates also produced lesions on nonwounded fruit tissues. No symptoms were observed on passion fruits, regardless of the inoculation method. Mycelial growth, sporulation, conidial germination, and/or appressorial formation of the seven Colletotrichum species were inhibited by azoxystrobin, difenoconazole, and thiophanate-methyl to varying degrees. The present study will contribute to the development of forecasting models based on prevailing weather of cashew cropping zones and improve cashew anthracnose management in Brazil.     

Southern bean Mosaic Virus the Causal Agent of a New Disease of Phaseolus vulgaris beans in Spain

Southern bean mosaic virus (SBMV) has been identified as the cause of a new disease in greenhouse-cultivated common bean (Phaseolus vulgaris), in the south-east of Spain. The identification was based on host range comparisons, morphological and serological characteristics of the virus, the size of its dsRNA species and the nucleotide sequence of an 810-bp fragment from ORF2. The virus could be clearly discriminated from the related sobemovirus Southern cowpea mosaic virus. This is the first report of SBMV in Spain.     

Fusarium oxysporum f.sp. cepae dynamics: in-plant multiplication and crop sequence simulations

To reduce Fusarium Basal Rot caused by Fusarium oxysporum f.sp. cepae (Foc) through crop rotation, plant species should be selected based on Foc multiplication in their roots. Foc multiplication rates in 13 plant species were tested in a greenhouse. All plant species enabled Foc multiplication. The lowest Foc levels (cfu g^?1 dry root) were found for wheat, sunflower, cowpea and millet, the highest for black bean. The highest Foc levels per plant were calculated for sudan grass. These data were used to calibrate the model Pf?=?Pi/(α?+?βPi) relating final (Pf) and initial (Pi) Foc levels in the soil. The rate of population increase at low Pi (1/α) was highest for onion and black oat and smallest for sunflower. The pathogen carrying capacity (1/β) was highest for black oat and black bean, and lowest for wheat, cowpea and foxtail millet. Foc soil population dynamics was simulated for crop sequences by concatenating Pi-Pf values, considering instantaneous or gradual pathogen release after harvest. Different soil Foc populations were attained after reaching steady states. Foc populations in the sequence onion –foxtail millet - wheat – cowpea were 67 % lower than in the sequence onion – sudan grass - black oat - black beans. In this work, by combining detailed greenhouse experiments with modelling, we were able to screen crops for their ability to increase Foc population and to explore potential crop sequences that may limit pathogen build-up.     

Hymenopterous parasitoids of the cherry bark tortrix, Enarmonia formosana (Scopoli) in central-east Europe (Hymenoptera, Ichneumonoidea; Lepidoptera, Tortricidae)

Strategies targeting the biological control of the cherry bark tortrix (=CBT), Enarmonia formosana (Scopoli) in North America have also included the search for potentially useful native hymenopterous parasitoids of the pest in Europe. The search for such agents undertaken in the central-east Europe (Czech Republic, Slovak Republic, Hungary) resulted in determination of several ichneumonid species (Campoplex cf. dubitator Horst., Liotryphon sp., Lissonotus sp., Pimpla spuria (Grav.), Pimpla turionellae (L.), and some others, and a braconid (Apanteles britannicus Wilk.) in 2001–2002.     

Hymenopterous parasitoids of the cherry bark tortrix, Enarmonia formosana (Scopoli) in central-east Europe (Hymenoptera, Ichneumonoidea; Lepidoptera, Tortricidae)

Strategies targeting the biological control of the cherry bark tortrix (=CBT), Enarmonia formosana (Scopoli) in North America have also included the search for potentially useful native hymenopterous parasitoids of the pest in Europe. The search for such agents undertaken in the central-east Europe (Czech Republic, Slovak Republic, Hungary) resulted in determination of several ichneumonid species (Campoplex cf. dubitator Horst., Liotryphon sp., Lissonotus sp., Pimpla spuria (Grav.), Pimpla turionellae (L.), and some others, and a braconid (Apanteles britannicus Wilk.) in 2001–2002.