Alfalfa establishment without tillage as influenced by insecticide and vegetation suppression

Conventional alfalfa ( Medicago sativa L.) establishment methods may create considerable potential for erosion. Conservation tillage practices that result in stand establishment without disturbing the soil greatly would be beneficial in reducing soil losses. Thus, field experiments were conducted to evaluate the success of alfalfa establishment without tillage in a perennial grass sod. Variables included rate of carbofuran (2, 3-dihydro-2, 2-dimethyl-7 benzofuranyi methylcarbamate) insecticide and control of existing vegetation with chemicals. Establishment without tillage was compared with a conventional method of establishment. Carbofuran at 1.1 kg ha⁻¹ applied in the row with the seed, when compared with a control, increased yields during the year of planting but no response was observed in the year after seeding. Yields of alfalfa established without tillage using either glyphosate ( N -(phosphonomethyl)glycine) or paraquat (1,1-dimethyl-4, 4-bipyridinium chloride) for sod suppression were equivalent to or better than yields obtained from conventional sowings except for the 2 April sowing. Paraquat was more effective for tall fescue (Festuca arundinacea Schreb.) suppression when applications were made on 26 April after spring tiller emergence was complete than on 2 April when some of the tillers may have been protected from the spray by basal sheath tissue.
Broadcast application of paraquat resulted in higher alfalfa yields and decreased non-alfalfa components due to more complete sod suppression than application in bands over the row.     

Verification of immunofluorescence colony-staining of Erwinia carotovora subsp. atroseptica by reisolation and immunodiffusion or PCR

In this study, the reliability and efficiency of three procedures for verification of IFC-positive colonies of Erwinia carotovora subsp. atroseptica were compared: (1) PCR amplification, (2) reisolation on a non-selective medium (trypticase soy agar) followed by direct immunodiffusion (TSA-DID), developed for isolation of target and cross-reacting bacteria, and (3) reisolation on a selective medium (crystal-violet pectate) and characterization of selected isolates with Ouchterlony double diffusion (DLCVP-ODD), developed for isolation of pectinolytic Erwinia spp. The reliability of a PCR amplification procedure for characterization of E.c. atroseptica was evaluated. Specific amplification products could be produced from DNA of all 187 European strains of the bacterium, while no amplification products were obtained from DNA of four distinctive serological groups of bacteria cross-reacting with antibodies against E.c. atroseptica , nor from DNA of randomly selected saprophytic bacteria isolated from potato peel extracts. All 60 immunofluorescent-positive target colonies from a potato peel extract with added E.c. atroseptica tested were positive by PCR compared with 68 and 72% successful determinations by TSA-DID and DLCVP-ODD, respectively. PCR enabled verification of fluorescent colonies from IFC preparations of naturally infected seed lots with an efficiency of 93%, compared with 48 and 71% successful determinations by TSA-DID and DLCVP-ODD, respectively. It is concluded that PCR is useful for routine confirmation of the identity of fluorescent colonies in IFC.     

Escherichia coli Isolates from Young Calves in Bavaria: In Vitro Susceptibilities to 14 Anti‐microbial Agents

During the occasional testing of Escherichiacoli from faecal samples of young calves we observed multi‐resistant isolates. Because of the significance of E. coli as an indicator bacterium for resistance trends we tested E. coli populations of young calves over a longer period. Here we present the results of a retrospective study comparing isolates from 1998 to 2000. Moreover, we compared, in a clinical study, the resistance rates of E. coli populations from 67 hospitalized calves both before and after hospitalization (with or without anti‐microbial therapy), and with their anamnestic data of antibiotic usage. The highest resistance rates were found to be more than 80% for tetracyclines, ampicillin, sulfonamide/trimethoprim combinations, and chloramphenicol. A significant increase or decrease over the years was not observed. In analysing the data of hospitalized calves, an increase of resistance to some anti‐microbials had to be registered that seemed to be connected with the selective pressure due to agents used in the clinic. In comparing anamnestic data and resistance rates it became obvious that reliable data are not easily available and that a number of potential anti‐microbial influence factors have to be taken into account.     

Microbiological, immunological and molecular methods suitable for commercial detection and quantification of the blackleg pathogen, Erwinia carotovora subsp. atroseptica, on seed potato tubers: a review

Contamination of seed potato tubers by Erwinia carotovora subsp. atroseptica is widespread with the bacteria usually sited superficially in lenticels and suberized wounds. As seed contamination level is related to blackleg incidence, seed health is best assessed by determining the number of cells of E. c. atroseptica per mL of tuber-peel extract. The relative specificity, sensitivity and ease of use of four recently developed microbiological, immunological and molecular methods to detect and/or quantify tuber contamination are discussed in relation to the testing of commercial seed stock. Sensitivities of all four methods are at or below the threshold level for blackleg development (< 10³ cells mL^-1), but there are differences regarding their specificity and ease of use. Three of them allow enumeration of most live cells of the bacterium, using specific monoclonal and polyclonal antibodies against the predominant serogroup I: (a) immunomagnetic separation of E. c. atroseptica before viable count on a selective-diagnostic growth medium, crystal violet pectate, (b) immunofluorescence staining and counting of colonies in pour-plate medium in tissue culture plates and (c) enrichment of the bacterium in peel-extract dilutions directly in microtitre plates prior to DAS-ELISA. In the fourth method, both live and dead cells are detected, but not quantified, by PCR amplification of target sequences using specific primers for E. c. atroseptica regardless of serogroup.