A computer-based system for the management of the rust disease of French prunes1

Rust (Tranzscheliu discolor) is the most important disease of French prunes in New South Wales (NSW), Australia. Infection by this fungus occurs only when leaves are wet. The length of time for which the leaves are wet and the temperature during such periods are major determinants of whether infection occurs and its likely severity. The use by prune growers of new rust management strategies depends on knowledge of infection events and therefore requires ready access to environmental data from orchards. To satisfy this need, microprocessor-based device called a Prune Rust Infection Predictor (PRIP) was developed. The instrument measures air temperature, rainfall, and the presence or absence of free water tree canopies. Measurements are taken at 5-min intervals during wet periods. The instrument calculates whether or not conditions have been suitable for rust infection and potential severity of infection. The system has been operated by advisory staff of NSW Agriculture Fisheries since the 1988/1989 growing season. Potential infection period and related environmental data are collected by personal computers via permanently installed telephone lines from PRIPs located within prune orchards. Prune growers are then advised by recorded telephone messages and given appropriate disease mangement advice. Cumulative potential infection period values are used to provide a prognosis of current-season rust epidemic severity. An expert system is also being developed to assist growers in making decisions on specific rust management options.     

Bacterial Isolates From Plaque and From Blood During and After Routine Dental Procedures in Dogs

Objective — This study evaluates the association between dental procedures and bacteremia in dogs, including a comparison of bacteria isolated from plaque and blood, severity of the bacteremia versus the severity of dental disease, and the longevity of bacteremia.
Study Design — Bacteria cultured from the blood over time were compared with those isolated from the plaque and crevicular fluid and in relation to severity of dental disease.
Animals or Sample Population — Twenty adult greyhounds.
Methods — Blood samples were collected for culture before induction of general anesthesia, immediately after intubation, 20 minutes after initiation of the dental procedure, and at 10-minute intervals until 10 minutes after the dental procedure was completed. Samples of plaque were taken for microbiological culture.
Results — Sixty to ninety percent of the bacterial genera isolated from the plaque were present in the blood. Dogs classified according to severity of dental disease showed no difference in the total number of different species or number of different Gram-negative, Gram-positive, or anaerobic bacteria isolated from plaque or blood (P <.05). Bacteremia was present in all of the dogs studied, within 40 minutes from the initiation of the dental procedure, regardless of the severity of oral disease.
Conclusions — Gram-negative, Gram-positive, and anaerobic bacteria are present in blood during dental procedures; the bacteremia can persist beyond the dental procedure, and is not associated with the severity of dental disease.
Clinical Relevance — The nature and extent of bacteremia occuring during routine dental procedures is important in understanding a potential risk to dogs.     

Leaf number as a criterion for determining defoliation time for Lolium perenne: 2. Effect of defoliation frequency and height

The object of this study was to determine the importance of frequency and height of defoliation on regrowth potential of Lolium perenne. Defoliation interval was based on stage of the regrowth cycle, as indicated by leaves per tiller.
Simulated swards of Lolium perenne cv Yatsyn were grown as individual plants in a glasshouse kept at a day/night temperature of 25°C/15°C.
Treatments imposed were defoliation at 2, 5 or 12 cm residual height, and low and high water soluble carbohydrate (WSC) level obtained by varying defoliation interval, i.e. defoliating at the 1-leaf or 3-leaf stage of the regrowth cycle. Regrowth after frequent short defoliations was only 65% of the less frequently defoliated plants taken over the full regrowth cycle. This was associated with a lower stubble WSC content (2·15 vs 17·5% in stubble) and a twenty-seven-fold difference in the amount of WSC in the stubble per plant. This difference in total WSC was a combined effect of more and heavier tillers and higher WSC content in stubble of plants defoliated less frequently at the end of the regrowth cycle. The regrowth of plants with WSC levels depleted by frequent defoliation when defoliated at 2 cm was significantly below that of those defoliated at 5 and 12 cm.
The results indicate the desirability of defoliating plants at the 3-leaf stage of the regrowth cycle. This not only allows the full regrowth potential to be expressed in that growth cycle, but also in the next cycle, by allowing the replenishment of WSC reserves and optimizing tiller status. The potential to regrow appears then to be based more on the total amount of WSC than the proportion of WSC in stubble.     

Pawns in the Game: Ports in a Global Transportation System

Abstract: Although they are required to make very large investments, port authorities are discovering that they have less and less control over their destinies. The major decisions affecting port traffic are made by shipping lines whose activities are global in scale. This paper examines the plight of public monopoly ports in a highly competitive environment. Several policy options are discussed.     

Leaf number as a criterion for determining defoliation time for Lolium perenne, 1. Effect of water-soluble carbohydrates and senescence

This study sought to define the optimum defoliation interval for Lolium perenne , with the maximum interval being determined by the onset of senescence, as reflected by the number of fully expanded leaves, and the minimum interval set by the replenishment of water-soluble carbohydrates (WSCs).
In a glasshouse set at 13°C/23°C night/day temperature and at a plant spacing of 94 m⁻² (3290 tillers m⁻²), the accumulation of dry matter against leaf number and days was exponential to the four-leaf stage of the regrowth cycle. Senescence commenced at the 3·5-leaf stage.
WSCs in roots, stubble and leaf showed a very significant linear relationship with leaf number. Levels of WSCs in leaves were restored to predefoliation values by the one-leaf stage, after which WSCs accumulated preferentially in the stubble, rising to 22% at the four-leaf stage.
Regrowth after 6 d was significantly greater for plants defoliated at the three-leaf stage than at the one-leaf stage, but this difference disappeared at the end of the regrowth cycle. This questions the importance of WSCs in determining the yield of ryegrass under normal rotational grazing management.
Regrowth at 6 d was related positively to stubble WSCs (r²= 0·66) and to stubble DM per tiller(r²=0·71)     

Phenotypic selection for seed dormancy in white snakeroot (Eupatorium rugosum)

Eupatorium rugosum (Ageratina altissima), commonly known as white snakeroot, is a weedy plant that invades woodland areas in North America, Korea, and Japan. In order to examine the inheritance of seed dormancy in this species, seeds from a single population were screened for their differential germination response to stratification. After two cycles of recurrent selection, the seed from the shallow–dormant lines had 4.4 times greater germination prior to stratification than did the seed from the deep–dormant lines. The seed from the deep–dormant lines showed 3.4 times greater germination after stratification, compared to the seed from the shallow–dormant selections. This suggests that primary dormancy in the seed of white snakeroot is under some degree of genetic control. This perennial species produces overwintering rhizomes that give rise to adventitious, vegetative buds each spring. The plants selected for the production of seeds with lower levels of dormancy in the fall were observed to generate rhizomatous buds that were released from dormancy earlier in spring, compared to the plants that produced seeds with higher levels of dormancy. A statistically significant positive correlation also was observed between seed and bud dormancy in a naturally occurring population of white snakeroot. Common regulatory elements might be influencing dormancy in both the seeds and vegetative buds of this species.