Search

An investigation into the effect of coloured mulch technology as a technique to control weeds when growing the essential oil plant, summer savory (Satureja hortensis) was made. As well as weed control, the effects on the production of crop biomass and essential oil content and quality were also considered. The mulch treatments produced significantly more biomass than either of the control treatments (which used no mulch either with or without herbicide). The white mulch treatment produced the greatest biomass, closely followed by the red mulch treatment. The blue mulch treatment was third in ranking, although not significantly greater than the black mulch. Estimates of the quantity of essential oil produced by each treatment followed a similar trend to that shown by biomass production.

Policy support for organic farming in the UK is based in part on the ability of organic farming systems to deliver natural heritage benefi ts. Most UK research on the natural heritage benefi ts of organic farming has addressed lowland arable systems. A reanalysis of a subset of data from a MAFF-funded study of biodiversity in England and Wales suggests that organic systems in predominantly pastoral landscapes may show similar biodiversity benefi ts to ones in predominantly arable landscapes. Future research needs to address organically managed pastoral, hill and upland systems across the UK.

Phosphorus (P) is an essential plant nutrient that needs to be managed carefully in organic systems so that crop yield and quality remain sustainable without contributing to environmental damage, particularly that associated with eutrophication. Under organic regulations, minimally processed rock phosphate (PR) can be used to amend low P fertility soils, although the solubility is extremely low at optimum soil pH for most crop growth (pH 6.5). This paper describes a project (PLINK) which aims to develop methods of improving P efficiency on organic farms, although the same approaches may also be applicable on conventional and low-input farms. The methodologies that the project is developing include the fermentation and composting of crop waste material with PR in order to solubilise P and make it more available to the crop. Some initial results are described here. In addition, the project will investigate the alteration of the rotation to include crops or varieties with high P uptake efficiency, or roots that possess acidifying properties which improve P availability for following crops.

The most effective way to control common scab is by irrigating a potato crop at tuber initiation. With the introduction of legislation such as the Water Framework Directive this will become increasingly difficult. In this field experiment, we assessed the potential of a number of non-water measures for controlling this disease. Common scab on daughter tubers at harvest was reduced by applying rapeseed meal at 1 t ha-1 to the beds and then incorporating it into the soil, and adding a mixture of Trichoderma viride isolates into the furrow at planting. None of these treatments was as effective as using water.

Papillomatous digital dermatitis (PDD), an emerging infectious disease of cattle, is characterized by painful, ulcerative foot lesions. The detection of high numbers of invasive spirochetes in PDD lesions suggests an important role for these organisms in the pathogenesis of PDD. PDD-associated spirochetes have phenotypic characteristics consistent with members of the genus Treponema. Partial 16S ribosomal DNA (rDNA) sequence analysis of clonal isolates from California cattle showed that they comprise three phylotypes which cluster closely with human-associated Treponema spp. of the oral cavity (T. denticola and T. medium/T. vincentii) or genital area (T. phagedenis). The goal of our study was to apply 16S-23S rDNA intergenic spacer region (ISR) sequence analysis to the molecular typing of U.S. PDD-associated Treponema isolates. This methodology has potentially greater discriminatory power for differentiation of closely related bacteria than 16S rDNA analysis. We PCR amplified, cloned, and sequenced the ISRs from six California PDD-associated Treponema isolates and, for comparative purposes, one strain each of T. denticola, T. medium, T. vincentii, and T. phagedenis. Two ISRs that varied in length and composition were present in all the PDD-associated Treponema isolates and in T. denticola, T. medium, and T. phagedenis. ISR1 contained a tRNAAla gene, while ISR2 contained a tRNAIle gene. Only a single ISR (ISR1) was identified in T. vincentii. Comparative analyses of the ISR1 and ISR2 sequences indicated that the California PDD-associated Treponema isolates comprised three phylotypes, in agreement with the results of 16S rDNA analysis. PCR amplification of the 16S-tRNAIle region of ISR2 permitted rapid phylotyping of California and Iowa PDD-associated Treponema isolates based on product length polymorphisms.

Trichomonad isolates from 14 virgin beef bulls in 3 California herds were submitted to the California Veterinary Diagnostic Laboratory for confirmation of a diagnosis of bovine trichomoniasis. Specimens were submitted in self-contained diagnostic pouches and produced cultures with a protozoan like Tritrichomonas foetus. Under bright-field microscopy, large numbers of single-celled motile organisms, approximately 12 μm x 9 μm, with multiple anterior flagellae, a posterior flagellum, axostyle, and a clearly visible undulating membrane were detected. Motility was jerky and rolling. Air-dried smears of cultures stained with Giemsa or Diff-Quick/iodine revealed an organism similar to T. foetus, although somewhat more rounded (less spindle-shaped). Several organisms appeared to have 4 flagellae, and there were numerous dark-staining bodies in the cytoplasm. Scanning electron micrographs (5000 X) clearly showed four anterior flagellae and an undulating membrane on most organisms, and an axostyle that was consistently longer than that seen in T. foetus. Specific primers for T. foetus were used in a polymerase chain reaction (PCR) assay. No amplification product was detected from any of the "virgin bull" isolates, while positive control isolates of T. foetus all yielded an amplicon of the expected size. On the basis of this partial morphological and molecular characterization, it was tentatively concluded that the isolated organism is not T. foetus, and speculate that it may be a commensal organism of the lower bowel. The recovery of non T. foetus trichomonads in a commercially available diagnostic system suggests that more specific methods may be needed for discrimination among trichomonads isolated from the preputial cavity of bulls., The Bovine Practitioner, Vol. 33, No. 2 (1999 May)

Peer-reviewed., Incidence of pea crab, Pinnotheres ostreum Say 1817, infestation in the eastern oyster, Crassostrea virginica (Gmelin, 1791), was recorded and related to oyster gametogenic activity over 18 months. Sampling occurred at twO tidal heights (high intertidal HI and low intertidal LI) at two sites (House Creek, HC and Skidaway River, SR) in Wassaw Sound, Georgia. Overall, incidence rates were 3% HC LI, 1 % HC HI, 8% SR LI, and 4% SR HI. At both tidal heights at HC, no differences were observed in gonad area between those oysters with and without pea crabs. At SR (where overall incidences were higher), oysters without pea crabs had significantly higher gonad area values than those oysters with pea crabs present. These results suggest that at higher incidences of pea crab infestation, oyster reproductive capabilities could be impacted, and support the claim that the pea crab/oyster relationship is a parasitic one.

Twenty-five cows were allotted to 3 groups : 1) treated with 10 g Lincomix® Soluble Powder (n=11), 2) treated with Terramycin-343® Soluble Powder (n=11), or 3) no treatment (n=3). Cows were placed on a hydraulic tilt-table at enrollment (d 1) and feet were examined. Cows with papillomatous digital dermatitis (PDD) on one or both rear feet were enrolled in the study., American Association of Bovine Practitioners Proceedings of the Annual Conference, 1998

Peer-reviewed, Growth of the Atlantic surfclam, Spisula solidissima solidissima, was compared with that of the southern Atlantic surfclam, Spisula solidissima similis. All experimental animals were reared in upweller units at 20°C and fed cultured algae on a daily basis. Over the 14 wk of the study, the Atlantic surf clams grew markedly better (8.9-mm increase in shell length and a 1,103% increase in biomass) than the southern Atlantic surfclams (6.6-mm increase in shell length and 573% mcrease in biomass). Mortality for both groups was negligible. The mean shell lengths attained for the Atlantic surfclams (15.3 mm) and the southern Atlantic surfclams (13 mm) at the conclusion of the study were large enough to ensure good growth and survival on relocation to a field growout environment. The growth patterns obtained under similm growth conditions further highlight some basic life history differences between these subspecies, which were apparent from other studies.

Peer-reviewed., Laboratory-spawned veliger-stage larvae of the southern Atlantic surfclam, Spisula solidissima similis (Say 1822), were reared to late pediveliger stage on five different cell concentrations of Tahitian strain Isochrysis species (T-Iso) to determine an optimal food ration for this subspecies. Larvae were fed daily 0, 50,000, 100,000, 200,000, or 300,000 cells/mL of T-Iso. Day-old veliger larvae were stocked in 150 (1-L) replicate flasks at mean densities of 0.7 or 0.8 larvae/mL for trials A and B, respectively. Larval growth and survival were assessed every 2 days over the 14-day trial penods. Significantly greater growth and survival of larvae occurred in both trials in the lower food rations of 50,000 and 100,000 cells/mL. A reduction in larval growth rate and survival was observed at the higher ration treatments. A decline in overall larval health may be associated with the deliterious effects of surplus ration degradation.

Peer-reviewed. © F.X. O'Beirn et al., 1997. Reproduced with the permission of the executive editor of the JNCAS., Recruitment, in 1992, of the eastern oyster, Crassostrea virginica, at one site (Flume Dock) within the Sapelo Island National Estuarine Research Reserve (SINERR) was lower than other sampling sites. Recruitment allied with gametogenesis and parasite (Perkinsus marinus) prevalence within the oysters was examined in 1993, in an attempt to explain the differences observed the previous year. Sampling occurred at three sites (Marsh Landing, Jack Hammock, and Flume Dock) along the Duplin River within the SINERR. Oyster recruitment in 1993 was reduced in all sites within the SINERR. No oyster recruitment was recorded at the Flume Dock site during any monthly collections or on collectors deployed for the duration of the sampling study. Oysters developed gametogenically and spawned at the Marsh Landing site two weeks prior to their occurrence at the Jack Hammock site. Gametogenic development in oysters at the Flume Dock site was retarded a further two weeks where the males appeared to spawn six weeks after the females, which could account for reduced recruitment levels at this site. Approximately, twice as many females as males occurred in all sites. Monthly sampling of prevalence and intensity of Perkinsus marinus (Dermo) revealed high levels of both parameters. Smaller oysters did display lower prevalences of Dermo than larger forms.