Simulating the evolution of glyphosate resistance in grains farming in northern Australia.

Background and Aims: The evolution of resistance to herbicides is a substantial problem in contemporary agriculture. Solutions to this problem generally consist of the use of practices to control the resistant population once it evolves, and/or to institute preventative measures before populations become resistant. Herbicide resistance evolves in populations over years or decades, so predicting the effectiveness of preventative strategies in particular relies on computational modelling approaches. While models of herbicide resistance already exist, none deals with the complex regional variability in the northern Australian sub-tropical grains farming region. For this reason, a new computer model was developed. Methods: The model consists of an age- and stage-structured population model of weeds, with an existing crop model used to simulate plant growth and competition, and extensions to the crop model added to simulate seed bank ecology and population genetics factors. Using awnless barnyard grass (Echinochloa colona) as a test case, the model was used to investigate the likely rate of evolution under conditions expected to produce high selection pressure. Key Results: Simulating continuous summer fallows with glyphosate used as the only means of weed control resulted in predicted resistant weed populations after approx. 15 years. Validation of the model against the paddock history for the first real-world glyphosate-resistant awnless barnyard grass population shows that the model predicted resistance evolution to within a few years of the real situation. Conclusions: This validation work shows that empirical validation of herbicide resistance models is problematic. However, the model simulates the complexities of sub-tropical grains farming in Australia well, and can be used to investigate, generate and improve glyphosate resistance prevention strategies.

The infectivity and host range of Orgyia anartoides nucleopolyhedrovirus.

The painted apple moth (PAM), Teia anartoides (Walker) (Lepidoptera: Lymantriidae) made a recent incursion into New Zealand. A nucleopolyhedrovirus (NPV), Orgyia anartoides NPV (OranNPV), originally isolated from PAM in Australia, was tested for its pathogenicity to PAM and a range of non-target insect species found in New Zealand, to evaluate its suitability as a microbial control for this insect invader. Dosage-mortality tests showed that OranNPV was highly pathogenic to PAM larvae; mean LT50 values for third instars ranged from 17.9 to 8.1 days for doses from 102 to 105 polyhedral inclusion bodies/larva, respectively. The cause of death in infected insects was confirmed as OranNPV. Molecular analysis established that OranNPV can be identified by PCR and restriction digestion, and this process complemented microscopic examination of infected larvae. No lymantriid species occur in New Zealand; however, the virus had no significant effects on species from five other lepidopteran families (Noctuidae, Tortricidae, Geometridae, Nymphalidae and Plutellidae) or on adult honeybees. Thus, all indications from this initial investigation are that OranNPV would be an important tool in the control of PAM in a future incursion of this species into New Zealand.

Development of profitable milk production systems for northern Australia: a field assessment of the productivity of five potential farming systems using farmlets.

Farmlets, each of 20 cows, were established to field test five milk production systems and provide a learning platform for farmers and researchers in a subtropical environment. The systems were developed through desktop modelling and industry consultation in response to the need for substantial increases in farm milk production following deregulation of the industry. Four of the systems were based on grazing and the continued use of existing farmland resource bases, whereas the fifth comprised a feedlot and associated forage base developed as a greenfield site. The field evaluation was conducted over 4 years under more adverse environmental conditions than anticipated with below average rainfall and restrictions on irrigation. For the grazed systems, mean annual milk yield per cow ranged from 6330 kg/year (1.9 cows/ha) for a herd based on rain-grown tropical pastures to 7617 kg/year (3.0 cows/ha) where animals were based on temperate and tropical irrigated forages. For the feedlot herd, production of 9460 kg/cow.year (4.3 cows/ha of forage base) was achieved. For all herds, the level of production achieved required annual inputs of concentrates of similar to 3 t DM/animal and purchased conserved fodder from 0.3 to 1.5 t DM/animal. This level of supplementary feeding made a major contribution to total farm nutrient inputs, contributing 50% or more of the nitrogen, phosphorus and potassium entering the farming system, and presents challenges to the management of manure and urine that results from the higher stocking rates enabled. Mean annual milk production for the five systems ranged from 88 to 105% of that predicted by the desktop modelling. This level of agreement for the grazed systems was achieved with minimal overall change in predicted feed inputs; however, the feedlot system required a substantial increase in inputs over those predicted. Reproductive performance for all systems was poorer than anticipated, particularly over the summer mating period. We conclude that the desktop model, developed as a rapid response to assist farmers modify their current farming systems, provided a reasonable prediction of inputs required and milk production. Further model development would need to consider more closely climate variability, the limitations summer temperatures place on reproductive success and the feed requirements of feedlot herds.

Germination, emergence, and persistence of Sonchus oleraceus, a major crop weed in subtropical Australia.

Sonchus oleraceus (common sowthistle) is a dominant weed and has increased in prevalence in conservation cropping systems of the subtropical grain region of Australia. Four experiments were undertaken to define the environmental factors that favor its germination, emergence, and seed persistence. Seeds were germinated at constant temperatures between 5 and 35C and water potentials between 0 and -1.4 MPa. The maximum germination rate of 86-100% occurred at 0 and -0.2 MPa, irrespective of the temperature when exposed to light (12 h photoperiod light/dark), but the germination rate was reduced by 72% without light. At water potentials of -0.6 to -0.8 MPa, the germination rate was reduced substantially by higher temperatures; no seed germinated at a water potential >-1.0 MPa. Emergence and seed persistence were measured over 30 months following seed burial at 0 (surface), 1, 2, 5, and 10 cm depths in large pots that were buried in a south-eastern Queensland field. Seedlings emerged readily from the surface and 1 cm depth, with no emergence from below the 2 cm depth. The seedlings emerged during any season following rain but, predominantly, within 6 months of planting. Seed persistence was short-term on the soil surface, with 2% of seeds remaining after 6 months, but it increased with the burial depth, with 12% remaining after 30 months at 10 cm. Thus, a minimal seed burial depth with reduced tillage and increased surface soil water with stubble retention has favored the proliferation of this weed in any season in a subtropical environment. However, diligent management without seed replenishment will greatly reduce this weed problem within a short period.

Emergence and seed persistence of Echinochloa colona, Urochloa panicoides and Hibiscus trionum in the sub-tropical environment of north-eastern Australia.

Better understanding of seed-bank dynamics of Echinochloa colona, Urochloa panicoides and Hibiscus trionum, major crop weeds in sub-tropical Australia, was needed to improve weed control. Emergence patterns and seed persistence were investigated, with viable seeds sown at different depths in large in-ground pots. Seedlings of all species emerged between October and March when mean soil temperatures were 21-23C. However, E. colona emerged as a series of flushes predominantly in the first year, with most seedlings emerging from 0-2 cm. Urochloa panicoides emerged mostly as a single large flush in the first two years, with most seedlings emerging from 5 cm. Hibiscus trionum emerged as a series of flushes over three seasons, initially with majority from 5 cm and then 0-2 cm in the later seasons. Longevity of the grass seed was short, with <5% remaining after burial at 0-2 cm for 24 months. In contrast, 38% of H. trionum seeds remained viable after the same period. Persistence of all species increased significantly with burial depth. These data highlight that management strategies need to be tailored for each species, particularly relating to the need for monitoring, application times for control tactics, impact of tillage, and time needed to reduce the seed-bank to low numbers.

Competition of sorghum cultivars and densities with Japanese millet (Echinochloa esculenta).

Field studies were conducted at two locations in southern Queensland, Australia during the 2003-2004 and 2004-2005 growing seasons to determine the differential competitiveness of sorghum (Sorghum bicolor L. Moench) cultivars and crop densities against weeds and the sorghum yield loss due to weeds. Weed competition was investigated by growing sorghum in the presence or absence of a model grass weed, Japanese millet (Echinochloa esculenta). The correlation analyses showed that the early growth traits (height, shoot biomass, and daily growth rate of the shoot biomass) of sorghum adversely affected the height, biomass, and seed production of millet, as measured at maturity. "MR Goldrush" and "Bonus MR" were the most competitive cultivars, resulting in reduced weed biomass, weed density, and weed seed production. The density of sorghum also had a significant effect on the crop's ability to compete with millet. When compared to the density of 4.5 plants per m2, sorghum that was planted at 7.5 plants per m2 suppressed the density, biomass, and seed production of millet by 22%, 27% and 38%, respectively. Millet caused a significant yield loss in comparison with the weed-free plots. The combined weed-suppressive effects of the competitive cultivars, such as MR Goldrush, and high crop densities minimized the yield losses from the weeds. These results indicate that sorghum competition against grass weeds can be improved by choosing competitive cultivars and by using a high crop density of > 7.5 plants per m2. These non-chemical options should be included in an integrated weed management program for better weed management, particularly where the control options are limited by the evolution of herbicide resistance.

Hydrofluoroalkanes as carrier solvents for timber preservation

Hydrofluoroalkanes are a specific category of hydrofluorocarbon (HFC) commonly used in refrigeration applications. Some HFCs hold potential for use as carrier fluids for preservatives used to protect timber above ground. They do not share the most significant disadvantages of currently used carriers for these applications. At ‘conventional’ operating pressures, they are capable of rapid, full penetration of some timbers generally considered refractory, such as spruce and the heartwood of radiata pine. But they are comparatively expensive and, while they are not detrimental to the ozone layer, they would contribute significantly to the greenhouse effect if released. Impregnation process conditions can be optimised to maximise biocide solubility and impregnation speed and depth.

A proposal to change existing virus species names to non-Latinized binomials.

A proposal has been posted on the ICTV website (2011.001aG.N.v1.binomial_sp_names) to replace virus species names by non-Latinized binomial names consisting of the current italicized species name with the terminal word "virus" replaced by the italicized and non-capitalized genus name to which the species belongs. If implemented, the current italicized species name Measles virus, for instance, would become Measles morbillivirus while the current virus name measles virus and its abbreviation MeV would remain unchanged. The rationale for the proposed change is presented.

Relative host plant species use by the lantana biological control agent Aconophora compressa (Membracidae) across its native and introduced ranges

Aconophora compressa Walker (Hemiptera: Membracidae) was released in 1995 against the weed lantana in Australia, and is now found on multiple host plant species. The intensity and regularity at which A. compressa uses different host species was quantified in its introduced Australian range and also its native Mexican range. In Australia, host plants fell into three statistically defined categories, as indicated by the relative rates and intensities at which they were used in the field. Fiddlewood (Citharexylum spinosum L.: Verbenaceae) was used much more regularly and at higher densities than any other host sampled, and alone made up the first group. The second group, lantana (Lantana camara L.: Verbenaceae; pink variety) and geisha girl (Duranta erecta L.: Verbenaceae), were used less regularly and at much lower densities than fiddlewood. The third group, Sheena’s gold (another variety of D. erecta), jacaranda (Jacaranda mimosifolia D. Don: Bignoniaceae) and myoporum (Myoporum acuminatum R. Br.: Myoporaceae), were used infrequently and at even lower densities. In Mexico, the insect was found at relatively low densities on all hosts relative to those in Australia. Densities were highest on L. urticifolia, D. erecta and Tecoma stans (L.) Juss. ex Kunth (Bignoniaceae), which were used at similar rates to one another. It was found also on a few other verbenaceous and non-verbenaceous host species but at even lower densities. The relative rate at which Citharexylum spp. and L. urticifolia were used could not be assessed in Mexico because A. compressa was found on only one plant of each species in areas where these host species co-occurred. The low rate at which A. compressa occurred on fiddlewood in Mexico is likely to be an artefact of the short-term nature of the surveys or differences in the suites of Citharexylum and Lantana species available there. These results provide further incentive to insist on structured and quantified surveys of non-target host use in the native range of potential biological control agents prior to host testing studies in quarantine.

DAQ00152 Herbicide Tolerance Screening in Northern Region (Phase IV)

The previous projects (phase I - III) highlighted that northern region wheat and barley cultivars differ considerably in their sensitivity to herbicides. The new project will focus on increased screening of advanced breeding lines and new cultivars lines to commonly used herbicides, for barley, chickpea and wheat. Studies on impact of environment on herbicide x genotype responses will also be undertaken with the national team. The new information will be added to the existing information package on herbicide tolerance. Thus, adverse impacts of herbicides on productivity in northern region will be reduced, as growers and agronomists will select safer herbicides for their sown variety, or select more tolerant varieties for their important herbicides.

Risk assessment and preventive strategies for herbicide resistance in NR (phase III)

The threat and management of glyphosate# resistant weeds are major issues facing northern region growers. At present five weeds are confirmed glyphosate-resistant: barnyard grass, liverseed grass, windmill grass, annual ryegrass and flaxleaf fleabane. This project used 25 experiments to investigate the ecology of the grass weeds, plus new or improved chemical and non-chemical control tactics for them. The refined glyphosate resistance model developed in this project used the experiments' findings to predict the long-term impacts on evolution of resistance and on seed bank numbers of resistant weeds. These data led to revised management and resistance avoidance strategies, which were published in the Reporter newsletter, and via an on-line risk assessment tool. - See more at: http://finalreports.grdc.com.au/UQ00054#sthash.oTkCN4Sk.dpuf

Improving Integrated Weed Management Practices in the Northern Region

Strategic research on developing and improving chemical and non-chemical tactics, weed ecology and herbicide application for problem and emerging weeds of summer fallows in the main cropping regions of the northern region.

Herbicide tolerance of barley and wheat cultivars in NR (phase III)

During the past 10 years, this project tested 23 barley and 51 wheat varieties with 19 and 34 registered herbicides, respectively. It concentrated on new varieties and herbicides. The research highlighted that Northern Region (NR) wheat and barley varieties differed considerably in their sensitivity to these herbicides. Overall, 9 per cent of wheat variety x herbicide combinations and 6 per cent of barley variety x herbicide combinations had significant yield losses (3 to 38%) from herbicides at recommended rates and crop stages. In addition, 21 to 23 per cent had significant yield losses from herbicides at double rates, indicating a narrow margin of crop safety.

2.2.2.2 Improved Management Summer Weeds: Best weed management strategies dryland cropping systems

To undertake a scoping study to identify the major issues in weed management in dryland cropping systems with cotton.

Effectiveness of Various Artificial Larval Diets for Rearing Bactrocera passiflorae (Froggatt) and B. xanthodes (Broun) in the Laboratory in Fiji

Laboratory colonies of Bactrocera passiflorae (Froggatt) and B. xanthodes (Broun) were established at Koronivia Research Station, Fiji in 1991. Laboratory rearing of the two economically important species was a prerequisite to studies conducted on protein bait spray and quarantine treatment development. To increase the production of laboratory reared fruit flies for this research and also to have a substitute larval diet available, replicated comparisons of the effectiveness of larval diets were carried out using B. passiflorae and B. xanthodes. The diets compared were pawpaw/bagasse, dehydrated carrot and diets used for culturing Mediterranean fruit fly (Ceratitis capitata Wiedemann), Oriental fruit fly (B. dorsalis Hendel), melon fly (B. cucurbitae Coquillett) and B. latifrons (Hendel), pawpaw diet and breadfruit diet. B. passiflorae and B. xanthodes eggs seeded onto the various diets were allowed to develop into larvae, pupae and adults. The percentage egg hatch, number of pupae recovered, percentage pupal mortality, weight of 100 pupae, number of adults and percentage eclosion were used to determine the effectiveness of the diets. Results showed that pawpaw/bagasse and dehydrated carrot diets performed favorably for both species. The pawpaw diet currently used as standard larval diets for both species is the most readily available and easiest to use. Breadfruit diet was tested on B. xanthodes only and showed that it was a suitable substitute for the pawpaw-based diets. Other larval diets, cassava/pawpaw and banana diets, that have been developed and used in the South Pacific areas are also discussed in this paper. When pawpaw or breadfruit are not available, dehydrated carrot diet may be substituted for fruit-based larval diets.