Uptake of chemicals from foliar deposits: Effects of plant species and molecular structure

The uptake from foliar deposits of 10 ¹⁴C-labelled compounds into each of 10 species of field-grown plants was measured 26 h after deposition by combustion of leaf tissue after removal of surface deposits. The compounds, which included eight pesticides, covered a wide range of lipophilicity and each was formulated in the same way; they were applied as droplets with a microsyringe. Uptake varied greatly between the species. All compounds were taken up well into maize and Xanthium pennsylvanicum, whereas relatively little entered the leaves of apple or orange. Uptake into the six other species varied according to the compound. Amongst the eight non-polar compounds, no relationship between the rate of uptake and molecular size was discerned, and only in X. pennsylvanicum was uptake related to the partition coefficient and water solubility. Considering all the compounds, weak relationships were observed between molecular cross-sectional area and uptake into four species. The range of the uptake rates (×130) was small compared with those of octan-1-ol-water partition coefficients (×10¹⁰) and water solublities (×10⁷) shown by the 10 compounds. Possible reasons for the absence of correlations between the uptake and the molecular properties considered are discussed. The results are consistent with either separate routes of cuticular entry for non-polar and polar compounds, or a common route for both types of compound. The generally poor uptake by apple and orange leaves, which may be related to their thick cuticles, highlights the need to develop special formulations to optimise uptake into these species.     

Using integrated population modelling to quantify the implications of multiple threatening processes for a rapidly declining population

Many species of conservation concern are in decline due to threats from multiple sources. To quantify the conservation requirements of these species we need robust estimates of the impact of each threat on the rate of population decline. However, for the vast majority of species this information is lacking. Here we demonstrate the application of integrated population modelling as a means of deriving robust estimates of the impact of multiple threats for a rapidly declining koala (Phascolarctos cinereus) population in South-east Queensland, Australia. Integrated population modelling provides a basis for reducing uncertainty and bias by formally integrating information from multiple data sources into a single model. We quantify mortality rates due to threats from dog attacks, vehicle collisions and disease and the extent to which each of these mortality rates would need to be reduced, or how much habitat would need to be restored, to stop the population declining. We show that the integrated population modelling approach substantially reduces uncertainty. We also show that recovery actions that only address single threats would need to reduce those threats to implausibly low levels to recover the population. This indicates that strategies for simultaneously tackling multiple threats are necessary; a situation that is likely to be true for many of the world’s threatened species. This study provides an important framework for quantifying the conservation requirements of species undergoing declines due to multiple threats.     

Field disease investigation-A differentiating and integrative approach to problems in animal populations

The economically important diseases of agricultural animals are those that affect groups of animals to result in impaired productivity or mortality. Herd and flock disease result from complex interactions between inciting agents (or other etiologies), and factors such as management systems, nutrition, environment and other contributory causes. For these reasons herd and flock disease problems must be addressed, researched, and taught, in the areas where they occur-on the farm and in the field. For political and educational reasons this needs to be on farms throughout the state or region represented by a veterinary school. Like most studies, this type of study needs to have a multidisciplinary input but these inputs often involve disciplines that are different from those that address clinical disease in individual animals in the veterinary teaching hospital setting. Clinical departments in veterinary schools have not traditionally found funds to support this approach to agricultural animal disease. This talk will discuss the establishment of a conjoint program between the College of Veterinary Medicine and the College of Agriculture at Washington State University (Field Disease Investigation Unit) to address these requirements and its activities over the past 25 years.     

Maturation and spawning performance of pond-reared Penaeus merguiensis in different combinations of temperature, light intensity and photoperiod

The combined effects of temperature (23 and 27 °C), light intensity (1100 and 2 lux or ≈ 21.5 and 0.04 μEinst m^?2 s respectively) and photoperiod (10 h light/14 h dark and 14 h light/10 h dark) on ovarian maturation and spawning performance of ablated pond‐reared Penaeus merguiensis were investigated in a 51‐day experiment. The results showed that temperature was the most influential factor, followed by light intensity, whereas the effect of photoperiod was minor. As the maturation process progressed, the effects of temperature and light intensity became stronger while that of photoperiod became less significant. Temperature significantly affected all the reproductive parameters assessed. Prawns in the 27 °C treatments outperformed those in the 23 °C treatments (P < 0.05). The effect of light intensity was found to have a significant effect (P < 0.05) only on the proportion of spawners (prawns that spawned) and spawning rate. More prawns spawned at a higher rate under dim light (2 lux) than under strong light (1100 lux). Photoperiod affected only the proportion of prawns reaching stage III of ovarian development (P < 0.05). There were interactions between temperature and light intensity affecting the proportion of prawns reaching stage III and, although not significantly, the proportion of spawners (P = 0.177), fecundity (P = 0.134) and survival (P = 0.061). Overall, it is recommended that a combination of 27 °C, 2 lux and 10 h light/14 h dark is suitable for the maturation of pond‐reared P. merguiensis. There were indications that temperature can be used to control the rate of ovarian maturation. Also, it is possible to increase light intensity up to 1100 lux in P. merguiensis hatcheries if prawns are ablated.     

Cold tolerance of the banana prawn Penaeus merguiensis de Man and its growth at different temperatures

Critical thermal minima (CTMin) were determined for subadults of Penaeus merguiensis acclimated at 15, 18, 21 and 24 °C for 3 weeks. The effect of cooling rate on CTMin was also investigated. The CTMin of prawns from these respective acclimation groups were 5.3, 6.0, 7.4, 9.0 and 4.7, 5.4, 6.0, 7.3 °C at the cooling rate of 1 °C h^?1 and 3 °C h^?1 respectively. Both acclimation temperature and cooling rate had a significant effect (P < 0.01) on the CTMin. Observation during the acclimation period showed that the growth rate of prawns acclimated at 24 °C was much higher than those acclimated at 21, 18 and 15 °C. The results indicate that P. merguiensis can overwinter in aquaculture ponds in south‐east Queensland, Australia, or other subtropical areas and attain good growth if simple overwintering facilities are available.     

Fitness characteristics of the European lineages of Phytophthora ramorum

As an introduced pathogen, Phytophthora ramorum exists as four near-clonal evolutionary lineages, of which only EU1 and EU2 are established in the UK. EU1 has become widespread since the first findings in 2002 whereas EU2, detected in 2011, has a more limited distribution. Both lineages are epidemic in plantation-grown larch, sporulating asexually on needles, but also causing heavy dieback and mortality. To understand whether EU1 and EU2 pose different threats to forest health, we compared their growth characteristics on agar, pathogenicity on several hosts, and sporulation on Japanese larch needles. When pathogenicity was evaluated by measuring colonization at 20 °C in mature bark (phloem) of Japanese and European larch (Larix kaempferi and L. decidua), English oak (Quercus robur), and beech (Fagus sylvatica), Japanese larch was the most susceptible and oak the least susceptible. On average, EU2 isolates produced significantly larger lesions than EU1 isolates in Japanese larch and oak although not in the other hosts. With tests using young saplings of Japanese and European larch, damaging bark lesions formed at both 10 °C and 20 °C, but EU2 was significantly more pathogenic at 20 °C on both hosts compared with EU1. In contrast, both lineages caused similar amounts of necrosis on inoculated leaves of rhododendron (Rhododendron ponticum). Moreover, EU2 isolates usually sporulated less abundantly on larch needles compared with EU1 isolates, suggesting a trade-off in pathogenicity and sporulation between lineages. As EU2 tends to have smaller sporangia than EU1, this could also reduce the inoculum potential of EU2.