Germination and hardseededness in desmanthus

The mechanisms and control of hardseededness in the 3 Australian cultivars of the genus Desmanthus were investigated in a series of experiments in which the effects of various seedsoftening treatments, particularly boiling water, were measured. Desmanthus seed is predominantly hard, only defective seeds being normally otherwise. As it has only very brief, early embryo dormancy, hardseededness is the only serious barrier to germination. Seed is most readily softened through rupture of the palisade at the lens (strophiole). The lens is of a typically mimosaceous type which is readily ruptured by immersion in boiling water or less readily by application of pressure to adjacent parts of the testa. Ruptures may consist only of separation of the palisade from underlying tissue, which alone does not confer permeability; mostly they also result in fractures to the palisade that then render seeds irreversibly permeable. The palisade becomes reflective as it separates, which allows the event to be witnessed at the moment of separation if suitable pressure is applied to the testa of an individual seed while it is viewed under magnification. Brief (4–10 seconds) immersion of highquality seed in boiling water consistently softened a high proportion of seeds without causing serious damage. Extending the duration of immersion led to a progressive increase in the proportion of seed deaths. Neither previous boiling water treatment nor scarification damage to the testa materially affected results of treatment, but immature and small seeds behaved differently, being more vulnerable to damage than mature seed, and less likely to undergo lens rupture. Adaptation of boiling water treatment to farm-scale seed handling was simple and reliable. Commercial treatment of seed by an alternative method suitable for greater bulks and consisting of passage through a rice-whitener was checked and found to be successful through a combination of gentle scarification and lens rupture, both attributable to the numerous minor impacts of the process. Percentage emergence of seedlings from soil in the greenhouse closely followed percentage laboratory germination, except when inferior seed grades were included in the comparison, when emergence was poor. Very little seed softened in soil. Already-permeable seed either germinated rapidly or died, while buried hard seed mostly remained hard and viable even more than a year after sowing.

The fishery and reproductive biology of Barking crayfish, Linuparus trigonus (Von Siebold, 1824) along Queenslands east coast

This paper describes the fishery and reproductive biology for Linuparus trigonus obtained from trawl fishermen operating off Queensland’s east coast, Australia. The smallest mature female lobster measured 59.8 mm CL, however, 50% maturity was reached between 80 and 85 mm CL. Brood fecundity (BF) was size dependent and ranged between 19,287 and 100,671 eggs in 32 females from 59.8 to 104.3 mm CL. The relationship was best described by the power equation BF = 0.1107*CL to the power of 2.9241 (r to the power of 2 = 0:74). Egg size ranged from 0.96 to 1.12 mm in diameter (mean = 1:02 (+or-) 0:01 mm). Egg weight and size were independent of lobster size. Length frequencies displayed multi-modal distributions.The percentage of female to male lobsters was relatively stable for small size classes (30 to 70 mm CL; 50.0 to 63.6% females), but female proportions rose markedly between 75 and 90 mm (72.2 to 85.4%) suggesting that at the onset of sexual maturity female growth rates are reduced. In size classes greater than 95 mm, males were numerically dominant. A description of the L. trigonus fishery in Queensland is also detailed.

Pesticide residues in food - acute dietary exposure

Consumer risk assessment is a crucial step in the regulatory approval of pesticide use on food crops. Recently, an additional hurdle has been added to the formal consumer risk assessment process with the introduction of short-term intake or exposure assessment and a comparable short-term toxicity reference, the acute reference dose. Exposure to residues during one meal or over one day is important for short-term or acute intake. Exposure in the short term can be substantially higher than average because the consumption of a food on a single occasion can be very large compared with typical long-term or mean consumption and the food may have a much larger residue than average. Furthermore, the residue level in a single unit of a fruit or vegetable may be higher by a factor (defined as the variability factor, which we have shown to be typically ×3 for the 97.5th percentile unit) than the average residue in the lot. Available marketplace data and supervised residue trial data are examined in an investigation of the variability of residues in units of fruit and vegetables. A method is described for estimating the 97.5th percentile value from sets of unit residue data. Variability appears to be generally independent of the pesticide, the crop, crop unit size and the residue level. The deposition of pesticide on the individual unit during application is probably the most significant factor. The diets used in the calculations ideally come from individual and household surveys with enough consumers of each specific food to determine large portion sizes. The diets should distinguish the different forms of a food consumed, eg canned, frozen or fresh, because the residue levels associated with the different forms may be quite different. Dietary intakes may be calculated by a deterministic method or a probabilistic method. In the deterministic method the intake is estimated with the assumptions of large portion consumption of a ‘high residue’ food (high residue in the sense that the pesticide was used at the highest recommended label rate, the crop was harvested at the smallest interval after treatment and the residue in the edible portion was the highest found in any of the supervised trials in line with these use conditions). The deterministic calculation also includes a variability factor for those foods consumed as units (eg apples, carrots) to allow for the elevated residue in some single units which may not be seen in composited samples. In the probabilistic method the distribution of dietary consumption and the distribution of possible residues are combined in repeated probabilistic calculations to yield a distribution of possible residue intakes. Additional information such as percentage commodity treated and combination of residues from multiple commodities may be incorporated into probabilistic calculations. The IUPAC Advisory Committee on Crop Protection Chemistry has made 11 recommendations relating to acute dietary exposure.

Recruitment and loss of juvenile stages of Helicoverpa spp. (Lepidoptera: Noctuidae) on contaminant plants in chickpea crops

The hypothesis that contaminant plants growing amongst chickpea serve as Helicoverpa sinks by diverting oviposition pressure away from the main crop was tested under field conditions. Gain (recruitment) and loss (presumed mortality) of juvenile stages of Helicoverpa spp. on contaminant faba bean and wheat plants growing in chickpea plots were quantified on a daily basis over a 12-d period. The possibility of posteclosion movement of larvae from the contaminants to the surrounding chickpea crop was examined. Estimated total loss of the census population varied from 80 to 84% across plots and rows. The loss of brown eggs (40–47%) contributed most to the overall loss estimate, followed by loss of white eggs (27–35%) and larvae (6–9%). The cumulative number of individuals entering the white and brown egg and larval stages over the census period ranged from 15 to 58, 10–48 and 1–6 per m row, respectively. The corresponding estimates of mean stage-specific loss, expressed as a percentage of individuals entering the stage, ranged from 52 to 57% for white eggs, 87–108% for brown eggs and 71–87% for first-instar larvae. Mean larval density on chickpea plants in close proximity to the contaminant plants did not exceed the baseline larval density on chickpea further away from the contaminants across rows and plots. The results support the hypothesis that contaminant plants in chickpea plots serve as Helicoverpa sinks by diverting egg pressure from the main crop and elevating mortality of juvenile stages. Deliberate contamination of chickpea crops with other plant species merits further investigation as a cultural pest management strategy for Helicoverpa spp.

A sampling technique for two-spotted mite in papaya

Two-spotted mite, Tetranychus urticae Koch, was until recently regarded as a minor and infrequent pest of papaya in Queensland through the dry late winter/early summer months. The situation has changed over the past 4-5 years, so that now some growers consider spider mites significant pests all year round. This altered pest status corresponded with a substantial increase in the use of fungicides to control black spot (Asperisporium caricae). A project was initiated in 1998 to examine the potential reasons for escalating mite problems in commercially-grown papaya, which included regular sampling over a 2 year period for mites, mite damage and beneficial arthropods on a number of farms on the wet tropical coast and drier Atherton Tableland. Differences in soil type, papaya variety, chemical use and some agronomic practices were included in this assessment. Monthly visits were made to each site where 20 randomly-selected plants from each of 2 papaya lines (yellow and red types) were surveyed. Three leaves were selected from each plant, one from each of the bottom, middle and top strata of leaves. The numbers of mobile predators were recorded, along with visual estimates of the percentage and age of mite damage on each leaf. Leaves were then sprayed with hairspray to fix the mites and immature predators to the leaf surface. Four leaf disks, 25 mm in diameter, were then punched from each leaf into a 50 ml storage container with a purpose-built disk-cutting tool. Disks from each leaf position were separated by tissue paper, within the container. On return to the laboratory, each leaf disk was scrutinised under a binocular microscope to determine the numbers of two-spotted mites and eggs, predatory mites and eggs, and the immature stages of predatory insects (mainly Stethorus, Halmus and lacewings). A total of 2160 leaf disks have been examined each month. All data have been entered into an Access database to facilitate comparisons between sites.

Role of Diadegma semiclausum (Hymenoptera: Ichneumonidae) in controlling Plutella xylostella (Lepidoptera: Plutellidae): Cage exclusion experiments and direct observation

We evaluated the role of the larval parasitoid, Diadegma semiclausum Hellén (Hymenoptera: Ichneumonidae), in controlling Plutella xylostella (L.) (Lepidoptera: Plutellidae) by cage exclusion experiments and direct field observation during the winter season in southern Queensland, Australia. The cage exclusion experiment involved uncaged, open cage and closed cage treatments. A higher percentage (54-83%) of P. xylostella larvae on sentinel plants were lost in the uncaged treatment than the closed (4-9%) or open cage treatments (11-29%). Of the larvae that remained in the uncaged treatment, 72-94% were parasitized by D. semiclausum, much higher than that in the open cage treatment (8-37% in first trial, and 38-63% in second trial). Direct observations showed a significant aggregation response of the field D. semiclausum populations to high host density plants in an experimental plot and to high host density plots that were artificially set-up near to the parasitoid source fields. The degree of aggregation varied in response to habitat quality of the parasitoid source field and scales of the manipulated host patches. As a result, density-dependence in the pattern of parasitism may depend on the relative degree of aggregation of the parasitoid population at a particular scale. A high degree of aggregation seems to be necessary to generate density-dependent parasitism by D. semiclausum. Integration of the cage exclusion experiment and direct observation demonstrated the active and dominant role of this parasitoid in controlling P. xylostella in the winter season. A biologically based IPM strategy, which incorporates the use of D. semiclausum with Bt, is suggested for the management of P. xylostella in seasons or regions with a mild temperature.

Effect of seasonal conditions on fleece weight and its components in merino sheep grazing Mitchell grass pasture in North West Queensland

SUMMARY Seasonal conditions in the pre to post natal period and selected periods before and during wool growth were described using climatic measures and estimates of the quality and quantity of pasture on offer derived from a validated pasture production model (GRASP). The variation in greasy and clean fleece weight, yield, staple length, fibre diameter, neck and side wrinkle score of Merinos grazing Mitchell grass in north west Queensland was explained in terms of these pasture and climatic measures and animal characteristics such as reproductive status, age and skin area. Multiple regression equations predicting clean and greasy fleece weight from the proportion of days in the wool growth period that the green pool in the pasture was less than one kg/ha, the percentage utilisation of the pasture, age, reproductive status and skin area of the ewes explained 87% and 79% of the variation respectively. Equations with similar predictors explained 58-85% of the variation of the other components. The inclusion of pasture conditions in the pre to post natal period did not significantly improve the predictions of the animal’s later performance. 22nd Biennial Conference.

Influence of Measured Characteristics on Price Received for Merino Wool from the Traprock Area of Southern Queensland

In this study of a commercial wool clip sold in the years 1991/92-1996/97, the effect of wool characteristics, (staple length, staple strength, fibre diameter, position of break, vegetable matter, hauteur, yield and coefficient of variation of staple length) on price was explored together with their effect on the ratio of price received per lot to the average weekly price (1994/95 basis) for clean wool of the same fibre diameter. Fibre diameter and where the point of break occurred had the most effect on price. As hauteur, staple length and yield increased, so did the price ratio but it decreased as the percentage of vegetable matter and the coefficient of variation of the staple length increased. The ratio of proceeds if all wool had been sold at average weekly market price, to proceeds if all wool had been 21µm or less, indicated little financial advantage over the six-year period as most sale lots were under 22µm. To raise the proceeds of sale above the proceeds estimated using average market price for each lot, the analyses suggested that hauteur, staple length and its coefficient of variation, could be considered, in addition to fibre diameter, when sourcing wethers for purchase. Animal production for a consuming world : proceedings of 9th Congress of the Asian-Australasian Association of Animal Production Societies [AAAP] and 23rd Biennial Conference of the Australian Society of Animal Production [ASAP] and 17th Annual Symposium of the University of Sydney, Dairy Research Foundation, [DRF]. 2-7 July 2000, Sydney, Australia.

VegMachine - putting pastoralists in the picture

Australia’s rangelands are the extensive arid and semi-arid grazing lands that cover approximately 70% of the Australian continent. They are characterised by low and generally variable rainfall, low productivity and a sparse population. They support a number of industries including mining and tourism, but pastoralism is the primary land use. In some areas, the rangelands have a history of biological decline (Noble 1997), with erosion, loss of perennial native grasses and incursion of woody vegetation commonly reported in the scientific and lay literature. Despite our historic awareness of these trends, the establishment of systems to measure and monitor degradation, has presented numerous problems. The size and accessibility of Australia’s rangeland often mitigates development of extensive monitoring programs. So, too, securing on-going commitment from Government agencies to fund rangeland monitoring activities have led to either abandonment or a scaled-down approach in some instances (Graetz et al. 1986; Holm 1993). While a multiplicity of monitoring schemes have been developed for landholders at the property scale, and some have received promising initial uptake, relatively few have been maintained for more than a few years on any property without at least some agency support (Pickup et al. 1998). But, ironically, such property level monitoring tools can contribute significantly to local decisions about stock, infrastructure and sustainability. Research in recent decades has shown the value of satellites for monitoring change in rangelands (Wallace et al. 2004), especially in terms of tree and ground cover. While steadily improving, use of satellite data as a monitoring tool has been limited by the cost of the imagery, and the equipment and expertise needed to extract useful information from it. A project now under way in the northern rangelands of Australia is attempting to circumvent many of the problems through a monitoring system that allows property managers to use long-term satellite image sequences to quickly and inexpensively track changes in land cover on their properties

Storage of Macadamia Nut-In-Shell

The effect of moisture content and storage temperature on the high quality storage life on macadamia nut-in-shell (NIS), and the subsequent influence of NIS storage on the shelf-life of roasted kernel, is being investigated. Macadamia integrifolia 'Keauhou" (HAES 246) NIS is being stored at 5°, 25°C and 40°C with a moisture content of 15.0, 12.5, 10.0, 7.5 and 3.5% for a maximum of 12 months. Preliminary results showed that unacceptable levels of visual mould developed on NIS with 15.0 and 12.5% moisture at 25°C following relatively short periods of storage. Discolouration and the production of an off-flavour in the raw kernel resulted after 1 month's storage of NIS with a moisture content of 10.0% at 40°C. Roasting times were reduced with increased storage duration of NIS with a moisture content of 15.0, 12.5 and 10.0% at 25°C, 15.0 and 12.5% at 5°C and 3.5% at 40°C. The percentage of roasted kernel rejects increased with increased storage duration of NIS with a moisture content of 15.0 and 12.5% at 25°C.

A new data source for fisheries resource assessment: genetic estimates of the effective number of spawners. Final Report to the Fisheries Research and Development Corporation.

The development of innovative methods of stock assessment is a priority for State and Commonwealth fisheries agencies. It is driven by the need to facilitate sustainable exploitation of naturally occurring fisheries resources for the current and future economic, social and environmental well being of Australia. This project was initiated in this context and took advantage of considerable recent achievements in genomics that are shaping our comprehension of the DNA of humans and animals. The basic idea behind this project was that genetic estimates of effective population size, which can be made from empirical measurements of genetic drift, were equivalent to estimates of the successful number of spawners that is an important parameter in process of fisheries stock assessment. The broad objectives of this study were to 1. Critically evaluate a variety of mathematical methods of calculating effective spawner numbers (Ne) by a. conducting comprehensive computer simulations, and by b. analysis of empirical data collected from the Moreton Bay population of tiger prawns (P. esculentus). 2. Lay the groundwork for the application of the technology in the northern prawn fishery (NPF). 3. Produce software for the calculation of Ne, and to make it widely available. The project pulled together a range of mathematical models for estimating current effective population size from diverse sources. Some of them had been recently implemented with the latest statistical methods (eg. Bayesian framework Berthier, Beaumont et al. 2002), while others had lower profiles (eg. Pudovkin, Zaykin et al. 1996; Rousset and Raymond 1995). Computer code and later software with a user-friendly interface (NeEstimator) was produced to implement the methods. This was used as a basis for simulation experiments to evaluate the performance of the methods with an individual-based model of a prawn population. Following the guidelines suggested by computer simulations, the tiger prawn population in Moreton Bay (south-east Queensland) was sampled for genetic analysis with eight microsatellite loci in three successive spring spawning seasons in 2001, 2002 and 2003. As predicted by the simulations, the estimates had non-infinite upper confidence limits, which is a major achievement for the application of the method to a naturally-occurring, short generation, highly fecund invertebrate species. The genetic estimate of the number of successful spawners was around 1000 individuals in two consecutive years. This contrasts with about 500,000 prawns participating in spawning. It is not possible to distinguish successful from non-successful spawners so we suggest a high level of protection for the entire spawning population. We interpret the difference in numbers between successful and non-successful spawners as a large variation in the number of offspring per family that survive – a large number of families have no surviving offspring, while a few have a large number. We explored various ways in which Ne can be useful in fisheries management. It can be a surrogate for spawning population size, assuming the ratio between Ne and spawning population size has been previously calculated for that species. Alternatively, it can be a surrogate for recruitment, again assuming that the ratio between Ne and recruitment has been previously determined. The number of species that can be analysed in this way, however, is likely to be small because of species-specific life history requirements that need to be satisfied for accuracy. The most universal approach would be to integrate Ne with spawning stock-recruitment models, so that these models are more accurate when applied to fisheries populations. A pathway to achieve this was established in this project, which we predict will significantly improve fisheries sustainability in the future. Regardless of the success of integrating Ne into spawning stock-recruitment models, Ne could be used as a fisheries monitoring tool. Declines in spawning stock size or increases in natural or harvest mortality would be reflected by a decline in Ne. This would be good for data-poor fisheries and provides fishery independent information, however, we suggest a species-by-species approach. Some species may be too numerous or experiencing too much migration for the method to work. During the project two important theoretical studies of the simultaneous estimation of effective population size and migration were published (Vitalis and Couvet 2001b; Wang and Whitlock 2003). These methods, combined with collection of preliminary genetic data from the tiger prawn population in southern Gulf of Carpentaria population and a computer simulation study that evaluated the effect of differing reproductive strategies on genetic estimates, suggest that this technology could make an important contribution to the stock assessment process in the northern prawn fishery (NPF). Advances in the genomics world are rapid and already a cheaper, more reliable substitute for microsatellite loci in this technology is available. Digital data from single nucleotide polymorphisms (SNPs) are likely to super cede ‘analogue’ microsatellite data, making it cheaper and easier to apply the method to species with large population sizes.

Fruit maturity and soundness relevant to feeding choice by fruit-piercing moths (Lepidoptera: Noctuidae) in citrus crops in northeast Australia

Fruit-piercing moths are significant pests of a range of fruit crops throughout much of the world's tropics and subtropics. Feeding damage by the adult moths is most widely reported in varieties of citrus. In the years 2003 and 2004, fruit-piercing moth activity was observed regularly at night in citrus crops in northeast Australia, to determine the level of maturity (based on rind colour) and soundness of fruit attacked. 'Navelina' navel and 'Washington' navel orange, grapefruit and mixed citrus crops were assessed, and fruit was rated and placed into five categories: green, colouring, ripe, overripe and damaged. There were no statistical differences in the percentage of fruit attacked in each category across crops. However, within the individual crops significant proportions of green 'Navelina' fruit (58.7%) and green mixed citrus (57.1%) were attacked in 2004. Among all the crops assessed, 25.1% of moth feeding occurred on overripe or damaged fruit. Crops started to be attacked at least 8 weeks before picking, but in two crops there were large influxes of moths (reaching 27 and 35 moths/100 trees, respectively) immediately before harvest. Moth activity was most intense between late February and late March. Eudocima fullonia (Clerck) represented 79.1% of all moths recorded on fruit, with Eudocima materna (L.), Eudocima salaminia (Cramer) and Serrodes campana (Guen.) the only other species observed capable of inflicting primary damage. Our results suggest that growers should monitor moth activity from 8 weeks before harvest and consider remedial action if moth numbers increase substantially as the crop matures or there is a history of moth problems. The number of fruit pickings could be increased to progressively remove ripe fruit or early harvest of the entire crop contemplated if late influxes of moths are known.

Aspects of reproduction and diet of the Australian endemic skate Dipturus polyommata (Ogilby) (Elasmobranchii: Rajidae), by-catch of a commercial prawn trawl fishery

The Australian endemic skate Dipturus polyommata collected from by-catch of a benthic prawn fishery off southern Queensland was examined to provide information on reproduction and diet. Morphological relationships of total length (LT) to disc width and LT to mass were estimated. Size at birth was estimated at c. 100-110 mm and size at first feeding at c. 105-110 mm LT. Size at 50% maturity (LT50 and 95% CI) was 321 (305-332) and 300 (285-306) mm LT for females and males, respectively. Size at first maturity corresponded to 87.7% of observed maximum size in females (366 mm LT) and 87.5% in males (343 mm L T). Two females, representing 18.2% of mature females sampled in the austral winter were each carrying two egg cases. Descriptions of egg cases are given. Diet described by the index of relative importance as a percentage (%IRI) was predominantly crustacean based with carid shrimps (53.64%) and penaeoid prawns (23.30%) the most significant prey groups. Teleosts (11.72%), gammarid amphipods (5.31%) and mysids (4.72%) were also important to the diet of the species, while a further six prey groups made only a minor contribution to diet (1.31%). An ontogenetic change was evident between the diets of immature and mature skates. Immature animals fed more extensively on carids and amphipods and mature animals on penaeoids, teleosts and mysids.

Distributions of lesser mealworm (Coleoptera: Tenebrionidae) in litter of a compacted earth floor broiler house in subtropical Queensland, Australia

Distributions of lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), in litter of a compacted earth floor broiler house in southeastern Queensland, Australia, were studied over two flocks. Larvae were the predominant stage recorded. Significantly low densities occurred in open locations and under drinker cups where chickens had complete access, whereas high densities were found under feed pans and along house edges where chicken access was restricted. For each flock, lesser mealworm numbers increased at all locations over the first 14 d, especially under feed pans and along house edges, peaking at 26 d and then declining over the final 28 d. A life stage profile per flock was devised that consisted of the following: beetles emerge from the earth floor at the beginning of each flock, and females lay eggs, producing larvae that peak in numbers at 3 wk; after a further 3 to 4 wk, larvae leave litter to pupate in the earth floor, and beetles then emerge by the end of the flock time. Removing old litter from the brooder section at the end of a flock did not greatly reduce mealworm numbers over the subsequent flock, but it seemed to prevent numbers increasing, while an increase in numbers in the grow-out section was recorded after reusing litter. Areas under feed pans and along house edges accounted for 5% of the total house area, but approximately half the estimated total number of lesser mealworms in the broiler house occurred in these locations. The results of this study will be used to determine optimal deployment of site-specific treatments for lesser mealworm control.

Spatio-temporal patterns in maturation of the chokka squid (Loligo vulgaris reynaudii) off the coast of South Africa

Knowledge of the temporal and spatial characteristics of chokka squid (Loligo vulgaris reynaudii) biology in South African waters is limited, so the possibility of there being a geographically fragmented stock was examined by investigating the distribution of maturity patterns for the species, covering all known spawning areas and using both historical and recent data. Gonadosomatic indices (GSI) varied between year-round consistency and apparent seasonal peaks in both summer and winter; there was no clear spatial pattern. Monthly percentage maturity provided further evidence for two peak reproductive periods each year, although mature squid were present throughout. Sex ratios demonstrated great variability between different areas and life history stages. Male-biased sex ratios were only apparent on the inshore spawning grounds and ranged between 1.118:1 and 4.267:1. Size at sexual maturity was also seasonal, squid maturing smaller in winter/spring than in summer/autumn. Also, squid in the east matured smaller than squid in the west. Although the results from the present study do not provide conclusive evidence of distinct geographic populations, squid likely spawn over a significantly larger area of the Agulhas Bank than previously estimated, and squid on the west coast of South Africa may return to spawn on the western portion of the Agulhas Bank. It remains likely, however, that the east and west coast populations are a single stock and that migration of juveniles to the west coast and their subsequent return as sub-adults is an integral but non-essential and variable part of the life history.