Use of standard toxicity tests with Typhlodromus pyri and Aphidius rhopalosiphi to establish a dose-response relationship     

C. Grimm  H. Schmidli  F. Bakker  K. Brown  P. Campbell  M. Candolfi  P. Chapman  E. G. Harrison  M. Mead-Briggs  R. Schmuck  A. Ufer 《Anzeiger für Sch?dlingskunde》2001,74(3):72-84

The existing standardised test systems for assessing the toxicity of crop protection products to the non-target arthropods Typhlodromus pyri (Acari: Phytoseiidae) and Aphidius rhopalosiphi (Hymenoptera: Aphidiidae) are limit tests designed to compare a single-use rate of the product with a water control. The suitability of these test systems for generating dose-response data as required for refined ecotoxicological risk assessment was evaluated. Data on dose-response toxicity of crop protection products to T. pyri and A. rhopalosiphi were generated under worst-case laboratory and to T. pyri under extended laboratory conditions and analysed using the standard Probit method, a logistic regression, a generalised Probit analysis, and the moving average-angle method in order to calculate the LR₅₀-values (application rate killing 50% of the exposed organisms). The fit of the models, the precision of the resulting LR₅₀ values, and the required minimum number of replicates were compared. In 85% of the studies, at least one of the statistical methods led to satisfactory results. The moving average-angle method was the most widely applicable method. The results show that the existing guidelines can be used to perform dose-response tests. Implications for risk assessment are discussed.  相似文献   

3. Determination of the sensitivity of Phytophthora infestans to phenylamides: a semi-quantitative test method     

C. NUNINGER†  N. BOLTON  J. J. DE  WIJS† T. STAUB† 《EPPO Bulletin》1992,22(2):309-311

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Induced resistance in host mixtures and its effect on disease control in computer-simulated epidemics     

C. LANNOU  C. DE  VALLAVIEILLE-POPE H. GOYEAU 《Plant pathology》1995,44(3):478-489

The epidemic simulator EPIMUL was modified and used to study how induced resistance affected the development of epidemics in host mixtures. In the model, induced resistance resulted from the interaction of host tissue with avirulent spores and caused a reduction in the efficacy of virulent spores deposited afterwards. We denned three parameters to describe induced resistance: the level of protection, defined as the magnitude of reduction in the virulent spore efficacy for infecting host tissue; the host surface area protected by an interaction with one avirulent spore; and the duration of protection of the host tissue, in days. In our simulations, induced resistance slowed the epidemics and gave better disease control in the mixtures, even if protection lasted for only 2 days. The disease reduction in the mixture attributable to induced resistance was approximately proportional to the level of protection. The effect of induced resistance increased as the protected area increased. Epidemics were virtually unaffected by induced resistance restricted to the infection site, but the effect of induced resistance initially increased rapidly as larger areas were protected. There was little further gain as the protected area increased from 2·6% to 26%. The influence of induced resistance was reduced when the interactions between virulent and avirulent pathogens were reduced.  相似文献   

Biological control of Fusarium oxysporum f. sp. lycopersici     

A. DE  CAL  S. PASCUAL  I. LARENA  P. MELGAREJO 《Plant pathology》1995,44(5):909-917

Fungi known to produce lytic enzymes were used in an attempt to control wilt of tomato caused by Fusarium oxysporum f. sp. lycopersici (FOL). Some of the fungal species (Penicillium oxalicum, Penicillium purpurogenum and Aspergillus nidulans) damaged hyphae of FOL in vitro and reduced the numbers of microconidia in the soil. Treatments with fungi did not result in a reduction in either chlamydospores of FOL in soil or populations of FOL in the rhizosphere of tomato. P. oxalicum was the most effective agent of biocontrol, and it reduced disease severity in both non-autoclaved (20% decrease) and sterile soil. In sterile soil, P. oxalicum reduced disease with different levels of severity (27% decrease at high levels and 50% decrease at low levels). Disease control by A. nidulans and P purpurogenum was only achieved when disease severity was low in sterile soil (55% and 45%, respectively).  相似文献   

Biological diversity of citrus tristeza virus (CTV) isolates in Spain   总被引：5，自引：1，他引：5  

J. F. BALLESTER-OLMOS  J. A. PINA  E. A. CARBONELL  P. MORENO  A. HERMOSO DE  MENDOZA  M. CAMBRA  L. NAVARRO 《Plant pathology》1993,42(2):219-229

A survey of citrus tristeza virus (CTV) isolates was carried out in most citrus-growing areas in Spain. Twenty-two isolates were selected by geographical origin, cultivar of source tree, and symptoms observed on the host or in preliminary tests, and were biologically characterized.
A wide range of variation in transmissibility by aphids and symptom intensity on nine different indicator species or scion-rootstock combinations was observed among CTV isolates. Mexican lime. Citrus macrophylla , and to a lesser extent citron were the most useful hosts for characterizing these isolates, and leaf symptoms and stem pitting were the most discriminating traits. Positive correlation was observed between symptoms induced on Mexican lime and C. macrophylla , but not between the symptoms induced on these indicators under greenhouse conditions and the homologous symptoms on plants grown in the screenhouse. Some of the traits studied enabled us to establish relatively well-defined groups of isolates, but in most cases a continuous range of variation was obtained and no clear group could be defined.  相似文献   

Windborne spread of ergot disease (Claviceps africana) in sorghum A-lines in Zimbabwe     

D. E. FREDERICKSON  P. G. MANTLE  W. A. J. DE  MILLIANO 《Plant pathology》1993,42(3):368-377

Ergot disease spread rapidly in Zimbabwe amongst replicated plots of male-sterile sorghum A-lines, from a group of centrally situated and precociously inoculated plants. Prominent secondary conidiation by the pathogen, Claviceps africana , on the surface of exuded honeydew provided airborne spores which were trapped in a Burkard continuous spore trap and showed diurnal peaks of concentration in air close to the primary source of inoculum. The rate of disease spread ( r =0·2; range 0·14–0·58) closely matched that recorded for other plant pathogens such as Phytophthora infestans and Puccinia graminis tritici , and it is concluded that the characteristic secondary conidia of C. africana were the principal epidemiological agents within the experimental area. Ergot spread by windborne secondary conidia has significant epidemiological and economic implications for sorghum hybrid breeding in southern Africa.  相似文献   

Racial diversity and complexity in regional populations of Erysiphe graminis f.sp. hordei in France over a 5-year period   总被引：2，自引：3，他引：2  

D. ANDRIVON  C. DE  VALLAVIEILLE-POPE 《Plant pathology》1993,42(3):443-464

The evolution of race patterns in three French regional populations of the barley powdery mildew pathogen Erysiphe graminis f.sp. hordei over a 5-year period showed rapid adaptation to newly introduced host resistance genes. In all three regions, the main change consisted of the replacement of initially abundant races by pathotypes differing markedly from them by their virulence gene combinations. This explained the increase in diversity during the first 3 years of the survey, when the second group of pathotypes became more common in the populations, and its subsequent decrease due to the decline of the first group of races. The mean number of virulence genes per isolate did not vary noticeably over time in the three populations, remaining at about four out of 12 genes tested. However, the distribution of the isolates into virulence complexity classes was greatly modified, fitting a binomial distribution by the end of the study, although significant deviations were apparent in the first 2 years (1986 and 1987). The data indicate that selection, migration and recombination are the most important factors shaping race structure and evolution in powdery mildew populations, and that mutation is of limited significance. No convincing evidence was obtained for the existence of stabilizing selection sensu Vanderplank as the mechanism limiting virulence complexity. Implications regarding spatial and temporal deployment of race-specific resistance genes to control powdery mildew are discussed.  相似文献   

Autosomal translocations in two exotic breeds of cattle in New Zealand     

A N Bruere  H M Chapman 《The Veterinary record》1973,92(23):615-618

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Efficiency of production and cow size in beef cattle     

D D Kress  E R Hauser  A B Chapman 《Journal of animal science》1969,29(3):373-383

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Extrapulmonary granulomatous lesions in canine paragonimiasis     

Hyong-sun Ah  W.L. Chapman 《Veterinary parasitology》1976,2(3):251-258

Extrapulmonary granulomatous lesions associated with a naturally acquired Paragonimus kellicotti infection were observed in a dog with severe pulmonary paragonimiasis. Lung lesions were similar to those previously described. Extrapulmonary granulomatous lesions were found in the liver, mediastinal lymph nodes, spermatic cord and the tunica vaginalis. Extravascular deposition of eggs in the spermatic cord and tunica vaginalis caused a perilymphatic granulomatous inflammation and partially occlusive lymphangitis with dilatation of the external lymphatic vessel of the right spermatic cord.  相似文献