First record of Nematospora coryli in Australia and its association with dry rot of Citrus

Nematospora (Eremothecium) coryli was isolated from Citrus and identified for the first time in Australia. This insect-transmitted yeast was associated with dry rot in cultivated and native Citrus fruits. Although N. coryli is known as a serious seed pathogen of many tropical and sub-tropical plants, evidence is presented that it has been present and undetected in Queensland for at least ninety years.

Timing of weaning and processing: effects on liveweight changes of weaner cattle

To reduce the number of musters and handling costs, calves in extensive cattle herds in northern Australia are processed (vaccinated, ear-marked, de-horned, branded and males castrated) shortly after they are weaned. As stress has adverse effects on health and growth, and weaning is a stressful time for calves, this experiment asked if calf health, welfare and performance were improved when calves had a period with their mothers post-processing, before they were weaned.

Survival and reproduction of Tribolium castaneum (Herbst), Rhyzopertha dominica (F.) and Sitophilus oryzae (L.) following periods of starvation

This study determined the starvation tolerance of Tribolium castaneum (Herbst), Rhyzopertha dominica (F.) and Sitophilus oryzae (L.) in terms of both adult survival and reproduction, the impact of starvation on reproduction not having been studied before. Experiments were conducted at 30°C and 55% or 70% r.h. using a laboratory strain and a field strain of each species. The number of progeny was a better indicator of the impact of starvation on a species than adult survival. Tribolium castaneum was the most tolerant species, requiring up to 35 d starvation before no progeny were produced. Rhyzopertha dominica and S. oryzae required up to 8 d starvation before no progeny were produced. The results suggest that hygiene will have a greater impact on populations of S. oryzae and R. dominica than T. castaneum.

Investigation of movement and factors influencing post-release survival of line-caught coral reef fish using recreational tag-recapture data

Six species of line-caught coral reef fish (Plectropomus spp., Lethrinus miniatus, Lethrinus laticaudis, Lutjanus sebae, Lutjanus malabaricus and Lutjanus erythropterus) were tagged by members of the Australian National Sportsfishing Association (ANSA) in Queensland between 1986 and 2003. Of the 14,757 fish tagged, 1607 were recaptured and we analysed these data to describe movement and determine factors likely to impact release survival. All species were classified as residents since over 80% of recaptures for each species occurred within 1 km of the release site. Few individuals (range 0.8-5%) were recaptured more than 20 km from their release point. L. sebae had a higher recapture rate (19.9%) than the other species studied (range 2.1-11.7%). Venting swimbladder gases, regardless of whether or not fish appeared to be suffering from barotrauma, significantly enhanced (P < 0.05) the survival of L. sebae and L. malabaricus but had no significant effect (P > 0.05) on L. erythropterus. The condition of fish on release, subjectively assessed by anglers, was only a significant effect on recapture rate for L. sebae where fish in "fair" condition had less than half the recapture rate of those assessed as in "excellent" or "good" condition. The recapture rate of L. sebae and L. laticaudis was significantly (P < 0.05) affected by depth with recapture rate declining in depths exceeding 30 m. Overall, the results showed that depth of capture, release condition and treatment for barotrauma influenced recapture rate for some species but these effects were not consistent across all species studied. Recommendations were made to the ANSA tagging clubs to record additional information such as injury, hooking location and hook type to enable a more comprehensive future assessment of the factors influencing release survival.

The mortality of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) neonate larvae in relation to drop-off and soil surface temperature: The dangers of bungy jumping

The first larval instar has been identified as a critical stage for population mortality in Lepidoptera, yet due to the body size of these larvae, the factors that contribute to mortality under field conditions are still not clear. Dispersal behaviour has been suggested as a significant, but ignored factor contributing to mortality in first-instar lepidopteran larvae. The impact that leaving the host plant has on the mortality rate of Helicoverpa armigera neonates was examined in field crops and laboratory trials. In this study the following are examined: (1) the effects of soil surface temperature, and the level of shade within the crop, on the mortality of neonates on the soil after dropping off from the host plant; (2) the percentage of neonates that dropped off from a host plant and landed on the soil; and (3) the effects of exposure to different soil surface temperatures on the development and mortality of neonates. The findings of this study showed that: (1) on the soil, surface temperatures above 43°C were lethal for neonates, and exposure to these temperatures contributed greatly to the overall mortality rate observed; however, the fate of neonates on the soil varied significantly depending on canopy closure within the crop; (2) at least 15% of neonates dropped off from the host plant and landed on the soil, meaning that the proportion of neonates exposed to these condition is not trivial; and (3) 30 min exposure to soil surface temperatures approaching the lethal level (>43°C) has no significant negative effects on the development and mortality of larvae through to the second instar. Overall leaving the plant through drop-off contributes to first-instar mortality in crops with open canopies; however, survival of neonates that have lost contact with a host plant is possible, and becomes more likely later in the crop growing season.

The effect of habitat and environmental history on otolith chemistry of barramundi Lates calcarifer in estuarine populations of a regulated tropical river

We examine the microchemistry of otoliths of cohorts of a fished shed population of the large catadromous fish, barramundi Lates calcarifer from the estuary of a large tropical river. Barramundi from the estuary of the large, heavily regulated Fitzroy River, north eastern Australia were analysed by making transects of 87Sr/86Sr isotope and trace metal/Ca ratios from the core to the outer edge. Firstly, we examined the Sr/Ca, Ba/Ca, Mg/Ca and Mn/Ca and 87Sr/86Sr isotope ratios in otoliths of barramundi tagged in either freshwater or estuarine habitats that were caught by the commercial fishery in the estuary. We used 87Sr/86Sr isotope ratios to identify periods of freshwater residency and assess whether trace metal/Ca ratios varied between habitats. Only Sr/Ca consistently varied between known periods of estuarine or freshwater residency. The relationships between trace metal/Ca and river flow, salinity, temperature were examined in fish tagged and recaptured in the estuary. We found weak and inconsistent patterns in relationships between these variables in the majority of fish. These results suggest that both individual movement history within the estuary and the scale of environmental monitoring were reducing our ability to detect any patterns. Finally, we examined fish in the estuary from two dominant age cohorts (4 and 7 yr old) before and after a large flood in 2003 to ascertain if the flood had enabled fish from freshwater habitats to migrate to the estuary. There was no difference in the proportion of fish in the estuary that had accessed freshwater after the flood. Instead, we found that larger individuals with each age cohort were more likely to have spent a period in freshwater. This highlights the need to maintain freshwater flows in rivers. About half the fish examined had accessed freshwater habitats before capture. Of these, all had spent at least their first two months in marine salinity waters before entering freshwater and some did not enter freshwater until four years of age. This contrasts with the results of several previous studies in other parts of the range that found that access to freshwater swamps by larval barramundi was important for enhanced population productivity and recruitment.

Use of part records in Merino breeding programs - The inheritance of wool growth and fibre traits during different times of the year to determine their value in Merino breeding programs

Fibre diameter can vary dramatically along a wool staple, especially in the Mediterranean environment of southern Australia with its dry summers and abundance of green feed in spring. Other research results have shown a very low phenotypic correlation between fibre diameter grown between seasons. Many breeders use short staples to measure fibre diameter for breeding purposes and also to promote animals for sale. The effectiveness of this practice is determined by the relative response to selection by measuring fibre traits on a full 12 months wool staple as compared to measuring them only on part of a staple. If a high genetic correlation exists between the part record and the full record, then using part records may be acceptable to identify genetically superior animals. No information is available on the effectiveness of part records. This paper investigated whether wool growth and fibre diameter traits of Merino wool grown at different times of the year in a Mediterranean environment, are genetically the same trait, respectively. The work was carried out on about 7 dyebanded wool sections/animal.year, on ewes from weaning to hogget age, in the Katanning Merino resource flocks over 6 years. Relative clean wool growth of the different sections had very low heritability estimates of less than 0.10, and they were phenotypically and genetically poorly correlated with 6 or 12 months wool growth. This indicates that part record measurement of clean wool growth of these sections will be ineffective as indirect selection criteria to improve wool growth genetically. Staple length growth as measured by the length between dyebands, would be more effective with heritability estimates of between 0.20 and 0.30. However, these measurements were shown to have a low genetic correlation with wool grown for 12 months which implies that these staple length measurements would only be half as efficient as the wool weight for 6 or 12 months to improve total clean wool weight. Heritability estimates of fibre diameter, coefficient of variation of fibre diameter and fibre curvature were relatively high and were genetically and phenotypically highly correlated across sections. High positive phenotypic and genetic correlations were also found between fibre diameter, coefficient of variation of fibre diameter and fibre curvature of the different sections and similar measurements for wool grown over 6 or 12 months. Coefficient of variation of fibre diameter of the sections also had a moderate negative phenotypic and genetic correlation with staple strength of wool staples grown over 6 months indicating that coefficient of variation of fibre diameter of any section would be as good an indirect selection criterion to improve stable strength as coefficient of variation of fibre diameter for wool grown over 6 or 12 months. The results indicate that fibre diameter, coefficient of variation of fibre diameter and fibre curvature of wool grown over short periods of time have virtually the same heritability as that of wool grown over 12 months, and that the genetic correlation between fibre diameter, coefficient of variation of fibre diameter and fibre curvature on part and on full records is very high (rg > 0.85). This indicates that fibre diameter, coefficient of variation of fibre diameter and fibre curvature on part records can be used as selection criteria to improve these traits. However, part records of greasy and clean wool growth would be much less efficient than fleece weight for wool grown over 6 or 12 months because of the low heritability of part records and the low genetic correlation between these traits on part records and on wool grown for 12 months.

Leaf-clearing and staining techniques for the observation of conidiophores in the Phyllactinioideae (Erysiphaceae)

Some whole leaf-clearing and staining techniques are described for the microscopic observation of the origin of powdery mildew conidiophores, whether from external mycelium or internal mycelium, emerging through stomata. These techniques enable separation of the two genera, Oidiopsis and Streptopodium, in the Erysiphaceae.

No-tillage and nitrogen application affects the decomposition of 15N-labelled wheat straw and the levels of mineral nitrogen and organic carbon in a Vertisol

No-tillage (NT) practice, where straw is retained on the soil surface, is increasingly being used in cereal cropping systems in Australia and elsewhere. Compared to conventional tillage (CT), where straw is mixed with the ploughed soil, NT practice may reduce straw decomposition, increase nitrogen immobilisation and increase organic carbon in the soil. This study examined 15N-labelled wheat straw (stubble) decomposition in four treatments (NT v. CT, with N rates of 0 and 75 kg/ha.year) and assessed the tillage and fertiliser N effects on mineral N and organic C and N levels over a 10-year period in a field experiment. NT practice decreased the rate of straw decomposition while fertiliser N application increased it. However, there was no tillage practice x N interaction. The mean residence time of the straw N in soil was more than twice as long under the NT (1.2 years) as compared to the CT practice (0.5 years). In comparison, differences in mean residence time due to N fertiliser treatment were small. However, tillage had generally very little effect on either the amounts of mineral N at sowing or soil organic C (and N) over the study period. While application of N fertiliser increased mineral N, it had very little effect on organic C over a 10-year period. Relatively rapid decomposition of straw and short mean residence time of straw N in a Vertisol is likely to have very little long-term effect on N immobilisation and organic C level in an annual cereal cropping system in a subtropical, semiarid environment. Thus, changing the tillage practice from CT to NT may not necessitate additional N requirement unless use is made of additional stored water in the soil or mineral N loss due to increased leaching is compensated for in N supply to crops.

Recovery of intravenously infused chromium EDTA and lithium sulphate in the urine of cattle and their use as markers to measure urine volume

A series of metabolism experiments investigated the recovery of continuous-, intravenously infused chromium complexed with ethylenediamine tetra-acetic acid (CrEDTA) and lithium sulphate in the urine of cattle with a view to using the markers to estimate urine and metabolite output in grazing cattle. The recovery of Cr in urine from these infusions was similar (90%) in metabolism trials when cattle consumed three very contrasting diets: high-grain formulated pellet, lucerne hay (Medicago sativa) or low-quality native grass hay (predominantly Heteropogon contortus). By contrast, Li recovery in urine averaged 46.3 +/- 0.40% and 72.6 +/- 0.43% for native pasture and lucerne hays, respectively, but was not constant across days. There was negligible transfer of Cr from CrEDTA in blood serum to the rumen or faeces, whereas appreciable quantities of infused Li were found in both. The ratio of urine volume estimated by spot samples and marker dilution of Cr, to urine volume measured gravimetrically, was 1.05. In grazing studies using rumen-fistulated (RF) steers grazing seven different tropical and temperate grass and legume pastures, the ratio of concentrations of purine derivatives (PD) to Cr in spot samples of urine was shown to vary diurnally in the range of 49% to 157% of the average 24 h value. This finding indicated the need for regular sampling of urine to achieve an accurate average value for the PD: Cr ratio in urine for use in estimating urinary PD excretion and hence microbial protein production in the rumen. It was concluded that continuous, intravenous infusion of CrEDTA resulted in a constant recovery of Cr in the urine of cattle across diets and, provided an intensive sampling regime was followed to account for diurnal variation, it would be suitable as a marker to estimate urine volume and urinary output of PD in grazing cattle.

Seasonal changes in pasture quality and diet selection and their relationship with liveweight gain of steers grazing tropical grass and grass-legume pastures in northern Australia.

The variation in liveweight gain in grazing beef cattle as influenced by pasture type, season and year effects has important economic implications for mixed crop-livestock systems and the ability to better predict such variation would benefit beef producers by providing a guide for decision making. To identify key determinants of liveweight change of Brahman-cross steers grazing subtropical pastures, measurements of pasture quality and quantity, and diet quality in parallel with liveweight were made over two consecutive grazing seasons (48 and 46 weeks, respectively), on mixed Clitoria ternatea/grass, Stylosanthes seabrana/grass and grass swards (grass being a mixture of Bothriochloa insculpta cv. Bisset, Dichanthium sericeum and Panicum maximum var. trichoglume cv. Petrie). Steers grazing the legume-based pastures had the highest growth rate and gained between 64 and 142 kg more than those grazing the grass pastures in under 12 months. Using an exponential model, green leaf mass, green leaf %, adjusted green leaf % (adjusted for inedible woody legume stems), faecal near infrared reflectance spectroscopy predictions of diet crude protein and diet dry matter digestibility, accounted for 77, 74, 80, 63 and 60%, respectively, of the variation in daily weight gain when data were pooled across pasture types and grazing seasons. The standard error of the regressions indicated that 95% prediction intervals were large (+/- 0.42-0.64 kg/head.day) suggesting that derived regression relationships have limited practical application for accurately estimating growth rate. In this study, animal factors, especially compensatory growth effects, appeared to have a major influence on growth rate in relation to pasture and diet attributes. It was concluded that predictions of growth rate based only on pasture or diet attributes are unlikely to be accurate or reliable. Nevertheless, key pasture attributes such as green leaf mass and green leaf% provide a robust indication of what proportion of the potential growth rate of the grazing animals can be achieved.

The impact of dry matter, ripeness and internal defects on consumer perceptions of avocado quality and intentions to purchase.

Insights into the relative importance of various aspects of product quality can be provided through quantitative analysis of consumer preference and choice of fruit. In this study, methods previously used to establish taste preferences for kiwifruit (Harker et al., 2008) and conjoint approaches were used to determine the influence of three key aspects of avocado quality on consumer liking and willingness to purchase fruit: dry matter percentage (DM), level of ripeness (firmness) and internal defects (bruising). One hundred and seven consumers tasted avocados with a range of DM levels from ~20% (minimally mature) to nearly 40% (very mature), and at a range of fruit firmness (ripeness) stages (firm-ripe to soft-ripe). Responses to bruising, a common quality defect in fruit obtained from the retail shelf, were examined using a conjoint approach in which consumers were presented with photographs showing fruit affected by damage of varying severity. In terms of DM, consumers showed a progressive increase in liking and intent to buy avocados as the DM increased. In terms of ripeness, liking and purchase intent was higher in avocados that had softened to a firmness of 6.5 N or below (hand-rating 5). For internal defects, conjoint analysis revealed that price, level of bruising and incidence of bruising all significantly lowered consumers' future purchase decision, but the latter two factors had a greater impact than price. These results indicate the usefulness of the methodology, and also provide realistic targets for Hass avocado quality on the retail shelf.

The effect of data sources and quality on the predictive capacity of CLIMEX models: an assessment of Teleonemia scrupulosa and Octotoma scabripennis for the biocontrol of Lantana camara in Australia

Understanding the effects of different types and quality of data on bioclimatic modeling predictions is vital to ascertaining the value of existing models, and to improving future models. Bioclimatic models were constructed using the CLIMEX program, using different data types – seasonal dynamics, geographic (overseas) distribution, and a combination of the two – for two biological control agents for the major weed Lantana camara L. in Australia. The models for one agent, Teleonemia scrupulosa Stål (Hemiptera:Tingidae) were based on a higher quality and quantity of data than the models for the other agent, Octotoma scabripennis Guérin-Méneville (Coleoptera: Chrysomelidae). Predictions of the geographic distribution for Australia showed that T. scrupulosa models exhibited greater accuracy with a progressive improvement from seasonal dynamics data, to the model based on overseas distribution, and finally the model combining the two data types. In contrast, O. scabripennis models were of low accuracy, and showed no clear trends across the various model types. These case studies demonstrate the importance of high quality data for developing models, and of supplementing distributional data with species seasonal dynamics data wherever possible. Seasonal dynamics data allows the modeller to focus on the species response to climatic trends, while distributional data enables easier fitting of stress parameters by restricting the species envelope to the described distribution. It is apparent that CLIMEX models based on low quality seasonal dynamics data, together with a small quantity of distributional data, are of minimal value in predicting the spatial extent of species distribution.

Issues and advances in the integrated control of sheep lice.

Ongoing pressure to minimise costs of production, growing markets for low residue and organic wool and meat, resistance to chemicals in louse populations, and the deregistration of diazinon for dipping and jetting have contributed to a move away from routine annual application of lousicides to more integrated approaches to controlling lice. Advances including improved methods for monitoring and detection of lice, an expanded range of louse control products and the availability of a web-accessible suite of decision support tools for wool growers (LiceBossTM) will aid this transition. Possibilities for the future include an on-farm detection test and non-chemical control methods. The design and extension of well-constructed resistance management programs to preserve the effectiveness of recently available new product groups should be a priority.

Investigations into the potential for mixed cultures of banana prawns Penaeus merguiensis, sea mullet Mugil cephalus and rabbitfish Siganus nebulosus for bioremediation of aquaculture waste

To experimentally investigate the potential of mixed species polycultures for bioremediation of nutrient rich prawn farm effluent, a series of experiments was performed with banana prawns Penaeus (Fenneropenaeus) merguiensis, sea mullet Mugil cephalus and rabbitfish Siganus nebulosus to determine their compatibilities during particular life stages. Rabbitfish demonstrated a high tendency to prey upon banana prawn juveniles when no other food was available. Mullet of various sizes did not appear to prey upon banana prawn postlarvae (PL16) or juveniles in a fed or unfed environment. The study confirms the good potential for mullet and banana prawn polycultures.