Biological control of parthenium (Parthenium hysterophorus) in Australian rangeland translates to improved grass production.

Biological control of parthenium, a major weed in grazing areas in Australia, was initiated in the mid 1970s. Since then, nine species of insects and two rust fungi have been introduced. Evaluation using pesticide exclusion at two sites (Mt. Panorama and Plain Creek) in Queensland, Australia, revealed that classical biological control had a significant negative effect on the target weed, but the impact varied between years. In this study, I quantified the effects of biological control of parthenium on grass production. Grass production declined with the increase in parthenium biomass. Significant increase in grass production due to biological control was observed, but only in 1 of 4 yr at Mt. Panorama and 2 of 4 yr at Plain Creek. At Mt. Panorama, there was a 40% increase in grass biomass in 1997 because of defoliation by Zygogramma bicolorata and galling by Epiblema strenuana. At Plain Creek, grass biomass increased by 52% in 1998 because of E. strenuana and by 45% in 2000 because of combined effects of E. strenuana and the summer rust Puccinia melampodii. This study provides evidence on the beneficial effects of biological control of parthenium in areas under limited grazing.

Effect of irrigation amounts applied with subsurface drip irrigation on corn evapotranspiration, yield, water use efficiency, and dry matter production in a semiarid climate

Quantifying the local crop response to irrigation is important for establishing adequate irrigation management strategies. This study evaluated the effect of irrigation applied with subsurface drip irrigation on field corn (Zea mays L.) evapotranspiration (ETc), yield, water use efficiencies (WUE = yield/ETc, and IWUE = yield/irrigation), and dry matter production in the semiarid climate of west central Nebraska. Eight treatments were imposed with irrigation amounts ranging from 53 to 356 mm in 2005 and from 22 to 226 mm in 2006. A soil water balance approach (based on FAO-56) was used to estimate daily soil water and ETc. Treatments resulted in seasonal ETc of 580-663 mm and 466-656 mm in 2005 and 2006, respectively. Yields among treatments differed by as much as 22% in 2005 and 52% in 2006. In both seasons, irrigation significantly affected yields, which increased with irrigation up to a point where irrigation became excessive. Distinct relationships were obtained each season. Yields increased linearly with seasonal ETc (R 2 = 0.89) and ETc/ETp (R 2 = 0.87) (ETp = ETc with no water stress). The yield response factor (ky), which indicates the relative reduction in yield to relative reduction in ETc, averaged 1.58 over the two seasons. WUE increased non-linearly with seasonal ETc and with yield. WUE was more sensitive to irrigation during the drier 2006 season, compared with 2005. Both seasons, IWUE decreased sharply with irrigation. Irrigation significantly affected dry matter production and partitioning into the different plant components (grain, cob, and stover). On average, the grain accounted for the majority of the above-ground plant dry mass (≈59%), followed by the stover (≈33%) and the cob (≈8%). The dry mass of the plant and that of each plant component tended to increase with seasonal ETc. The good relationships obtained in the study between crop performance indicators and seasonal ETc demonstrate that accurate estimates of ETc on a daily and seasonal basis can be valuable for making tactical in-season irrigation management decisions and for strategic irrigation planning and management.

The influence of planting density on the production of 'Goldfinger' (Musa spp., AAAB) in the subtropics

'Goldfinger', a tetraploid banana produced from the Fundación Hondureña de Investigación Agrícola (FHIA) breeding program, was released to the Australian industry in 1995. It was promoted as an apple-flavoured dessert banana with resistance to Fusarium wilt race 1 and subtropical race 4, as well as resistance to black and yellow Sigatoka (Mycosphaerella fijiensis and M. musicola, respectively). This study was initiated to provide agronomic information to the banana industry, which was under threat from Fusarium wilt, on a new cultivar which could replace 'Williams' (AAA, Cavendish subgroup) or 'Lady Finger' (AAB, Pome subgroup) in those areas affected by Fusarium wilt. Also few studies had reported on the production characteristics of the new tetraploid hybrids, especially from subtropical areas, and therefore two field sites, one a steep-land farm and the other a level, more productive site, were selected for planting density and spatial arrangement treatments. The optimum density in terms of commercial production, taking into account bunch weight, finger size, length of the production cycle, plant height and ease of management, was 1680 plants/ha on the steep-land site where plants were planted in single rows with 2.5 m × 2.5 m spacings. However on the level site a double-row triangular layout with inter-row distances of 4.5 m to allow vehicular access (1724 plants/ha) gave the best results. With this arrangement plants were in an alternate, triangular arrangement along a row and a spacing of 1.5 m between plants at the points of each triangle and between each block of triangles.

Native cut foliage production using Proteaceae species - A research summary

The Queensland Department of Primary Industries and Fisheries in collaboration with the Rural Industries Research and Development Corporation and Yuruga Nursery Pty Ltd have been conducting research into the development of five native foliage products. The three species and two cultivars being developed for commercial production are: Grevillea baileyana, Lomatia fraxinifolia, Athertonia diversifolia, Stenocarpus 'Forest Lace' and Stenocarpus 'Forest Gem'. Previous research involved an evaluation of 21 species from which these five were selected based on market comments, post harvest life and ability to grow under a range of climatic conditions. Lomatia fraxinifolia, Grevillea baileyana and Athertonia diversifolia are all native to north Queensland rainforests. Stenocarpus 'Forest Gem' and Stenocarpus 'Forest Lace' are hybrids and have been selected by Yuruga Nursery Pty Ltd. Both Stenocarpus cultivars are protected by Plant Breeders Rights. Current research into the commercial development of these species involves: market research, post harvest trials, field trials and grower training. Two field trials have been established on the Atherton Tablelands, one in the high rainfall zone at Yungaburra and the other in the low rainfall zone west of Mareeba. Field trials will evaluate the effects of fertiliser rates and pruning techniques on yield. Pests and diseases will be identified and appropriate control measures tested on trial plants. Vase life evaluations have also been carried out and the results indicate that the five foliages have exceptional vase life. All five products are being sold on the Australian domestic market in small volumes at this stage; it is anticipated that sales will significantly increase in the coming years. A number of leading exporters have indicated that the foliages may also meet the requirements of export markets. Stenocarpus 'Forest Gem' is similar in appearance to Persoonia longifolia (Barker Bush), which is a bush-picked foliage currently exported from Australia to a number of overseas markets.

Beyond chemical dependency for managing plant-parasitic nematodes: Examples from the banana, pineapple and vegetable industries of tropical and subtropical Australia

Plant-parasitic nematodes are important pests of horticultural crops grown in tropical and subtropical regions of Australia. Burrowing nematode (Radopholus similis) is a major impediment to banana production and root-knot nematodes (predominantly Meloidogyne javanica and M. incognita) cause problems on pineapple and a range of annual vegetables, including tomato, capsicum, zucchini, watermelon, rockmelon, potato and sweet potato. In the early 1990s, nematode control in these industries was largely achieved with chemicals, with methyl bromide widely used on some subtropical vegetable crops, ethylene dibromide applied routinely to pineapples and non-volatile nematicides such as fenamiphos applied up to four times a year in banana plantations. This paper discusses the research and extension work done over the last 15 years to introduce an integrated pest management approach to nematode control in tropical and subtropical horticulture. It then discusses various components of current integrated pest management programs, including crop rotation, nematode monitoring, clean planting material, organic amendments, farming systems to enhance biological suppression of nematodes and judicious use of nematicides. Finally, options for improving current management practices are considered.

Analysis of high yielding maize production - A study based on a commercial crop

This paper reports on the use of APSIM - Maize for retrospective analysis of performance of a high input, high yielding maize crop and analysis of predicted performance of maize grown with high inputs over the long-term (>100 years) for specified scenarios of environmental conditions (temperature and radiation) and agronomic inputs (sowing date, plant population, nitrogen fertiliser and irrigation) at Boort, Victoria, Australia. It uses a high yielding (17 400 kg/ha dry grain, 20 500 kg/ha at 15% water) commercial crop grown in 2004-05 as the basis of the study. Yield for the agronomic and environmental conditions of 2004-05 was predicted accurately, giving confidence that the model could be used for the detailed analyses undertaken. The analysis showed that the yield achieved was close to that possible with the conditions and agronomic inputs of 2004-05. Sowing dates during 21 September to 26 October had little effect on predicted yield, except when combined with reduced temperature. Single year and long-term analyses concluded that a higher plant population (11 plants/m2) is needed to optimise yield, but that slightly lower N and irrigation inputs are appropriate for the plant population used commercially (8.4 plants/m2). Also, compared with changes in agronomic inputs increases in temperature and/or radiation had relatively minor effects, except that reduced temperature reduces predicted yield substantially. This study provides an approach for the use of models for both retrospective analysis of crop performance and assessment of long-term variability of crop yield under a wide range of agronomic and environmental conditions.

Host plant resistance in grain crops and prospects for invertebrate pest management in Australia: An overview

An integrated pest management (IPM) approach that relies on an array of tactics is adopted commonly in response to problems with pesticide-based production in many agricultural systems. Host plant resistance is often used as a fundamental component of an IPM system because of the generally compatible, complementary role that pest-resistant crops play with other tactics. Recent research and development in the resistance of legumes and cereals to aphids, sorghum midge resistance, and the resistance of canola varieties to mite and insect pests have shown the prospects of host plant resistance for developing IPM strategies against invertebrate pests in Australian grain crops. Furthermore, continuing advances in biotechnology provide the opportunity of using transgenic plants to enhance host plant resistance in grains.

Alkaloid production by isolates of the sorghum ergot pathogen (Claviceps africana) from Australia and other countries

Isolates of Claviceps africana from Australia, Africa, Asia, and America were tested for the production of dihydroergosine (DHES), and its biogenic precursors dihydroelymoclavine (DHEL) and festuclavine (FEST), in culture. Several growth media were evaluated to optimise alkaloid production with little success. The best of these involved 2-stage culturing on high-sucrose substrate. Australian C. africana isolates varied widely and inconsistently in alkaloid production, with DHES concentrations in mycelium ranging from: <0.1 to 9 mg DHES/kg; <0.1 to 1.6 mg DHEL/kg; and <0.1 to 0.4 mg FEST/kg. In a separate experiment using similar culturing techniques, DHES was produced by 2 of 3 Australian isolates, 1 of 3 USA isolates, 1 of 4 Indian isolates, the sole Puerto Rican isolate, the sole Japanese isolate, but not the sole South African isolate. In this experiment, DHES concentrations detected in mycelium of Australian isolates (0.1-1.0 mg DHES/kg) were of similar magnitude to isolates from other countries (0.2-1.8 mg DHES/kg). Three C. africana isolates, including one that produced only traces of alkaloid in culture after 8 weeks, were inoculated onto panicles of sterile male sorghum plants. After 8 weeks, all 3 isolates produced 10-19 mg DHES/kg in the panicles, demonstrating that the growing plant favoured more consistent alkaloid production than culture medium.

Sustaining productivity of a Vertosol at Warra, Queensland, with fertilisers, no-tillage or legumes. 9. Production and nitrogen benefits from mixed grass and legume pastures in rotation with wheat

Reduced supplies of nitrogen (N) in many soils of southern Queensland that were cropped exhaustively with cereals over many decades have been the focus of much research to avoid declines in profitability and sustainability of farming systems. A 45-month period of mixed grass (purple pigeon grass, Setaria incrassata Stapf; Rhodes grass, Chloris gayana Kunth.) and legume (lucerne, Medicago sativa L.; annual medics, M. scutellata L. Mill. and M. truncatula Gaertn.) pasture was one of several options that were compared at a fertility-depleted Vertosol at Warra, southern Queensland, to improve grain yields or increase grain protein concentration of subsequent wheat crops. Objectives of the study were to measure the productivity of a mixed grass and legume pasture grown over 45 months (cut and removed over 36 months) and its effects on yield and protein concentrations of the following wheat crops. Pasture production (DM t/ha) and aboveground plant N yield (kg/ha) for grass, legume (including a small amount of weeds) and total components of pasture responded linearly to total rainfall over the duration of each of 3 pastures sown in 1986, 1987 and 1988. Averaged over the 3 pastures, each 100 mm of rainfall resulted in 0.52 t/ha of grass, 0.44 t/ha of legume and 0.97 t/ha of total pasture DM, there being little variation between the 3 pastures. Aboveground plant N yield of the 3 pastures ranged from 17.2 to 20.5 kg/ha per 100 mm rainfall. Aboveground legume N in response to total rainfall was similar (10.6 - 13.2 kg/ha. 100 mm rainfall) across the 3 pastures in spite of very different populations of legumes and grasses at establishment. Aboveground grass N yield was 5.2 - 7.0 kg/ha per 100mm rainfall. In most wheat crops following pasture, wheat yields were similar to that of unfertilised wheat except in 1990 and 1994, when grain yields were significantly higher but similar to that for continuous wheat fertilised with 75 kg N/ha. In contrast, grain protein concentrations of most wheat crops following pasture responded positively, being substantially higher than unfertilised wheat but similar to that of wheat fertilised with 75 kg N/ha. Grain protein averaged over all years of assay was increased by 25 - 40% compared with that of unfertilised wheat. Stored water supplies after pasture were < 134mm (< 55% of plant available water capacity); for most assay crops water storages were 67 - 110 mm, an equivalent wet soil depth of only 0.3 - 0.45 m. Thus, the crop assays of pasture benefits were limited by low water supply to wheat crops. Moreover, the severity of common root rot in wheat crop was not reduced by pasture - wheat rotation.

Effect of micro-propagation on the health status of strawberry planting material for commercial production of strawberry runners for Queensland

Plant tissue culture has been used for a number of years to produce micropropagated strawberry plants for planting into runner growing beds in the Stanthorpe (Queensland) and Bothwell (Tasmania) regions. This process has allowed the rapid release of new cultivars from the LAWS (Late Autumn, Winter, Spring) breeding program into the current runner production system. Micro-propagation in vitro allows plants to be produced during the autumn and winter months, when mother plants would normally be in a fruit production phase in the field in Queensland. The plants produced are of a high health status when they are planted. The subsequent arrival and build up of various diseases in the runner fields are closely monitored. Using tissue culture for the first generation reduces the time the plants spend in the field by twelve months, reducing disease incidence. To date, any disease outbreak has been successfully managed using early detection and rapid response methods.

Toughening of Fibre Composite Resins through Modification of Plant Oils

Extract from the executive summary: A collaborative scoping research project to identify plant oil species with potential value in the production of fibre composite resins and assess their suitability to Queensland’s regions has been conducted by QDPI&F, USQ and Loc Composites Pty Ltd. The use of plant-oil based resins in the production of fibre composites will contribute to the Queensland economy through establishing sustainable high technology building products from renewable sources while decreasing the reliance of resin production on fossil fuels. The main objective of this project was to indentify a suite of plant oil species that show agronomic adaptability to the Australian environment (e.g. climate, soils) and economic viability of extracting plant oils for resin production within a highly competitive supply and demand production market.

Characterising insect plant host relationships facilitates understanding multiple host use

Weed biocontrol relies on host specificity testing, usually carried out under quarantine conditions to predict the future host range of candidate control agents. The predictive power of host testing can be scrutinised directly with Aconophora compressa, previously released against the weed Lantana camara L. (lantana) because its ecology in its new range (Australia) is known and includes the unanticipated use of several host species. Glasshouse based predictions of field host use from experiments designed a posteriori can therefore be compared against known field host use. Adult survival, reproductive output and egg maturation were quantified. Adult survival did not differ statistically across the four verbenaceous hosts used in Australia. Oviposition was significantly highest on fiddlewood (Citharexylum spinosum L.), followed by lantana, on which oviposition was significantly higher than on two varieties of Duranta erecta (‘‘geisha girl’’ and ‘‘Sheena’s gold’’; all Verbenaceae). Oviposition rates across Duranta varieties were not significantly different from each other but were significantly higher than on the two non-verbenaceous hosts (Jacaranda mimosifolia D. Don: Bignoneaceae (jacaranda) and Myoporum acuminatum R. Br.: Myoporaceae (Myoporum)). Production of adult A. compressa was modelled across the hosts tested. The only major discrepancy between model output and their relative abundance across hosts in the field was that densities on lantana in the field were much lower than predicted by the model. The adults may, therefore, not locate lantana under field conditions and/or adults may find lantana but leave after laying relatively few eggs. Fiddlewood is the only primary host plant of A. compressa in Australia, whereas lantana and the others are used secondarily or incidentally. The distinction between primary, secondary and incidental hosts of a herbivore species helps to predict the intensity and regularity of host use by that herbivore. Populations of the primary host plants of a released biological control agent are most likely to be consistently impacted by the herbivore, whereas secondary and incidental host plant species are unlikely to be impacted consistently. As a consequence, potential biocontrol agents should be released only against hosts to which they have been shown to be primarily adapted.

Seed production of Stylosanthes guyanensis. 1. Growth and development.

The pattern of growth and development of seed crops of stylo (Stylosanthes guyanensis) was derived from measurements made on experimental and commercial crops in north Queensland. The three cultivars Cook, Endeavour, and Schofield differed appreciably only in the timetable of their development. Each had distinct successive phases of vegetative and reproductive development culminating in total annual seed production of 700-800 kg ha-1 from a healthy closed canopy, the main recorded cause of reduced production being the disease Botrytis sp. In a healthy crop of Cook, the peak quantity of standing seed represented almost 90 per cent of the total accountable seed, and the rise to and decline from this peak proceeded at rates of the order of 3-4 per cent per day. It is deduced that, although there appears to be little potential for either increase in overall production or improvement in synchronization or retention characteristics beyond that currently attained by a closed canopy of healthy plants, there is scope for an increase in the efficiency of recovery of standing seed. Maximum recovery will be achieved through attention to choice of time of harvest, presentation of a minimum amount of extraneous vegetation to the harvester, and improvement in harvester separation.

Seed production of Stylosanthes guyanensis. 2. The consequences of defoliation.

The consequences of defoliation on seed production of stylo (Stylosanthes guyanensis) were examined in field experiments at Walkamin in north Queensland. The practical aim of defoliation is to present a level uncompacted crop canopy to the harvester without a reduction in the quantity of seed carried at harvest ripeness. It was concluded that the latest date at which defoliation is reasonably certain to achieve its objectives is about four weeks before first flower initiation. In north Queensland, this means late February for cvv. Cook and Endeavour and early April for cv. Schofield. The results suggest that development of the population of individual shoots must be synchronized to produce the highest peaks of standing seed; that this is best achieved by ensuring that a closed crop canopy with a ceiling shoot population exists at the time of first flower initiation; and that poorly synchronized shoot development is a consequence of defoliating too late and a cause of reduced seed production.

Seed production of Stylosanthes guyanensis. 3. Effects of pre-harvest desiccation.

Strips within commercial crops of Stylosanthes guyanensis in the Mareeba district of north Queensland were sprayed with diquat 4, 6 and 10 days before harvest and compared with unsprayed strips. Pre-harvest desiccation made combine harvesting easier, but did not increase harvest yield. Where seed formation and maturation was still possible, desiccation prevented this without substantially increasing the loss of seed to the ground; increased harvest efficiency was thus offset by a diminished quantity of standing seed. However, where there was little or no further potential for seed development, diquat had virtually no effect on the quantity of standing seed or harvest efficiency. It was concluded that the results warranted neither recommendation nor further evaluation of preharvest desiccation of S. guyanensis seed crops.