Ecological significance of rice (Oryza sativa) planting density and nitrogen rates in managing the growth and competitive ability of itchgrass (Rottboellia cochinchinensis) in direct-seeded rice systems

Current understanding is that high planting density has the potential to suppress weeds and crop-weed interactions can be exploited by adjusting fertilizer rates. We hypothesized that (a) high planting density can be used to suppress Rottboellia cochinchinensis growth and (b) rice competitiveness against this weed can be enhanced by increasing nitrogen (N) rates. We tested these hypotheses by growing R. cochinchinensis alone and in competition with four rice planting densities (0, 100, 200, and 400 plants m-2) at four N rates (0, 50, 100, and 150 kg ha-1). At 56 days after sowing (DAS), R. cochinchinensis plant height decreased by 27-50 %, tiller number by 55-76 %, leaf number by 68-84 %, leaf area by 70-83 %, leaf biomass by 26-90 %, and inflorescence biomass by 60-84 %, with rice densities ranging from 100 to 400 plants m-2. All these parameters increased with an increase in N rate. Without the addition of N, R. cochinchinensis plants were 174 % taller than rice; whereas, with added N, they were 233 % taller. Added N favored more weed biomass production relative to rice. R. cochinchinensis grew taller than rice (at all N rates) to avoid shade, which suggests that it is a "shade-avoiding" plant. R. cochinchinensis showed this ability to reduce the effect of rice interference through increased leaf weight ratio, specific stem length, and decreased root-shoot weight ratio. This weed is more responsive to N fertilizer than rice. Therefore, farmers should give special consideration to the application timing of N fertilizer when more N-responsive weeds are present in their field. Results suggest that the growth and seed production of R. cochinchinensis can be decreased considerably by increasing rice density to 400 plants m-2. There is a need to integrate different weed control measures to achieve complete control of this noxious weed.

Aiming for the management of the small hive beetle, Aethina tumida, using relative humidity and diatomaceous earth

Small hive beetles (SHBs) are a global pest of European honeybee colonies. In the laboratory, the survival of adult SHBs was evaluated in relation to relative humidity (RH = 56, 64, 73, 82 and 96 %) and treatment with diatomaceous earth (DE) across 4 days. Low RH reduced survival. The application of DE reduced survival in addition to RH. Adults treated with corn flour (control) showed no difference in survival from untreated beetles. Scanning electron microscopy images showed no scarification of adult beetle cuticle after exposure to DE; therefore, water loss is likely facilitated through non-abrasive means such as the adsorption of cuticular lipids. The data agree with the hypothesis that DE causes mortality through water loss from treated insects. Egress, ingress, mortality and the egg-laying behaviours of beetles were observed in relation to a popular in-hive trench trap with and without the addition of DE. Traps filled with DE resulted in 100 % mortality of beetles compared with 8.6 % mortality when no DE was present. A simple method for visually determining beetle sex was used and documented.

Planet of the cavendish - understanding the domination

Those seeking to bring change to cultivars sold in the banana markets of the world have encountered major difficulties over the years. Change has been sought because of production difficulties caused by banana diseases such as Fusarium wilt or a desire to invigorate a stagnant market and obtain a competitive advantage by the introduction of diversity of product. Currently the world banana scene is dominated by cultivars from the Cavendish subgroup with their production in excess of 40% of total world production of banana and plantain combined, and in most western countries Cavendish is synonymous with banana. But Cavendish production usually necessitates very regular applications of pesticides, particularly fungicides for Mycosphaerella leaf spots control. So genetic resistance to these and other diseases would be very beneficial to minimizing costs of production, as well as reducing health risks to banana workers and the general population and minimizing impacts on the environment. In recent years, the overall market sales of some crops, such as tomatoes, have increased by providing diversity of cultivars to consumers. Can the same be done for banana? Perhaps a better understanding of how we have arrived at our current situation and the forces that have shaped our preference for Cavendish will allow us to plan more strategic crop improvement research which has enhanced chances of adoption by the banana industries of the world. A scoping study was recently undertaken in Australia to determine the current market opportunity for alternative cultivars and provide a roadmap for the industry to successfully develop this market. A multidisciplinary team reviewed the literature, surveyed the supply chain, analyzed gross margins and conducted consumer and sensory evaluations of 'new' cultivars. This has provided insight on why Cavendish dominates the market, which is the focus of this paper, and we believe will provide a solid foundation for future progress.

Dietary media for mass rearing of rusty grain beetle, Cryptolestes ferrugineus (Stephens) and flat grain beetle, Cryptolestes pusillus (Schonherr) (Coleoptera: Cucujidae)

We developed a suitable diet for mass rearing of Cryptolestes ferrugineus (Stephens) populations under laboratory conditions. Recently, this pest has developed strong level of resistance to phosphine in Australia, and therefore, a significant amount of research has been directed towards its management. In total, nineteen grain-based diets, containing rolled oats, various combinations of cracked grains and flours of wheat, sorghum, maize and barley were tested. Each diet contained a small proportion of wheat germ (4.5% w/w) and torula yeast (0.5% w/w). Experiments were conducted at fixed temperature and relative humidity regimes of 30 ± 2 °C and 70 ± 2%, respectively, and replicated three times. Adults (n = 40) of a laboratory strain of C. ferrugineus were introduced into each diet, removed after 14 days and total numbers of live adult progeny were recorded. The following diets resulted in highest live progeny production: barley flour (95%) (607.67 ± 11.21) = rolled oats (75%) + cracked sorghum (20%) (597.33 ± 33.79) ≥ wheat flour (47.5%) + barley flour (47.5%) (496.67 ± 52.93) > cracked sorghum (95%) (384.00 ± 60.66). The performance of these four diets was then tested with field-collected populations of C. ferrugineus and Cryptolestes pusillus (Schonherr). The diets based on rolled oats + cracked sorghum, wheat flour + barley flour, and barley flour alone consistently produced highest progeny numbers in field-collected populations of both species, with mean progeny numbers ranging from 359.9 to 478.5. The multiplication of C. pusillus was significantly higher than C. ferrugineus on all four diets. Our findings will help in mass rearing of healthy cultures of C. ferrugineus and C. pusillus that will greatly facilitate laboratory and field research and in particular, in developing management tactics for these species.

Do Phosphine Resistance Genes Influence Movement and Dispersal Under Starvation?

Phosphine resistance alleles might be expected to negatively affect energy demanding activities such as walking and flying, because of the inverse relationship between phosphine resistance and respiration. We used an activity monitoring system to quantify walking of Rhyzopertha dominica (F.) and a flight chamber to estimate their propensity for flight initiation. No significant difference in the duration of walking was observed between the strongly resistant, weakly resistant, and susceptible strains of R. dominica we tested, and females walked significantly more than males regardless of genotype. The walking activity monitor revealed no pattern of movement across the day and no particular time of peak activity despite reports of peak activity of R. dominica and Tribolium castaneum (Herbst) under field conditions during dawn and dusk. Flight initiation was significantly higher for all strains at 28 degrees C and 55% relative humidity than at 25, 30, 32, and 35 degrees C in the first 24 h of placing beetles in the flight chamber. Food deprivation and genotype had no significant effect on flight initiation. Our results suggest that known resistance alleles in R. dominica do not affect insect mobility and should therefore not inhibit the dispersal of resistant insects in the field.

Ecology, Behaviour and Control of Apis cerana with a Focus on Relevance to the Australian Incursion

Apis cerana Fabricius is endemic to most of Asia, where it has been used for honey production and pollination services for thousands of years. Since the 1980s, A. cerana has been introduced to areas outside its natural range (namely New Guinea, the Solomon Islands, and Australia), which sparked fears that it may become a pest species that could compete with, and negatively affect, native Australian fauna and flora, as well as commercially kept A. mellifera and commercial crops. This literature review is a response to these concerns and reviews what is known about the ecology and behaviour of A. cerana. Differences between temperate and tropical strains of A. cerana are reviewed, as are A. cerana pollination, competition between A. cerana and A. mellifera, and the impact and control strategies of introduced A. cerana, with a particular focus on gaps of current knowledge.

Evaluation of the efficacy and economics of irrigation management, plant resistance and Brassica(spot)(TM) models for management of white blister on Brassica crops

Options for the integrated management of white blister (caused by Albugo candida) of Brassica crops include the use of well timed overhead irrigation, resistant cultivars, programs of weekly fungicide sprays or strategic fungicide applications based on the disease risk prediction model, Brassica(spot)(TM). Initial systematic surveys of radish producers near Melbourne, Victoria, indicated that crops irrigated overhead in the morning (0800-1200 h) had a lower incidence of white blister than those irrigated overhead in the evening (2000-2400 h). A field trial was conducted from July to November 2008 on a broccoli crop located west of Melbourne to determine the efficacy and economics of different practices used for white blister control, modifying irrigation timing, growing a resistant cultivar and timing spray applications based on Brassica(spot)(TM). Growing the resistant cultivar, 'Tyson', instead of the susceptible cultivar, 'Ironman', reduced disease incidence on broccoli heads by 99 %. Overhead irrigation at 0400 h instead of 2000 h reduced disease incidence by 58 %. A weekly spray program or a spray regime based on either of two versions of the Brassica(spot)(TM) model provided similar disease control and reduced disease incidence by 72 to 83 %. However, use of the Brassica(spot)(TM) models greatly reduced the number of sprays required for control from 14 to one or two. An economic analysis showed that growing the more resistant cultivar increased farm profit per ha by 12 %, choosing morning irrigation by 3 % and using the disease risk predictive models compared with weekly sprays by 15 %. The disease risk predictive models were 4 % more profitable than the unsprayed control.

Networks of stored grain diseases and pests: Strategies for sampling and mitigation

Pathogens and pests of stored grains move through complex dynamic networks linking fields, farms, and bulk storage facilities. Human transport and other forms of dispersal link the components of this network. A network model for pathogen and pest movement through stored grain systems is a first step toward new sampling and mitigation strategies that utilize information about the network structure. An understanding of network structure can be applied to identifying the key network components for pathogen or pest movement through the system. For example, it may be useful to identify a network node, such as a local grain storage facility, through which grain from a large number of fields will be accumulated and move through the network. This node may be particularly important for sampling and mitigation. In some cases more detailed information about network structure can identify key nodes that link two large sections of the network, such that management at the key nodes will greatly reduce the risk of spread between the two sections. In addition to the spread of particular species of pathogens and pests, we also evaluate the spread of problematic subpopulations, such as subpopulations with pesticide resistance. We present an analysis of stored grain pathogen and pest networks for Australia and the United States.

Panel of real-time PCRs for the multiplexed detection of two tomato-infecting begomoviruses and their cognate whitefly vector species

A new approach for the simultaneous identification of the viruses and vectors responsible for tomato yellow leaf curl disease (TYLCD) epidemics is presented. A panel of quantitative multiplexed real-time PCR assays was developed for the sensitive and reliable detection of Tomato yellow leaf curl virus-Israel (TYLCV-IL), Tomato leaf curl virus (ToLCV), Bemisia tabaci Middle East Asia Minor 1 species (MEAM1, B biotype) and B.tabaci Mediterranean species (MED, Q biotype) from either plant or whitefly samples. For quality-assurance purposes, two internal control assays were included in the assay panel for the co-amplification of solanaceous plant DNA or B.tabaci DNA. All assays were shown to be specific and reproducible. The multiplexed assays were able to reliably detect as few as 10 plasmid copies of TYLCV-IL, 100 plasmid copies of ToLCV, 500fg B.tabaci MEAM1 and 300fg B.tabaci MED DNA. Evaluated methods for routine testing of field-collected whiteflies are presented, including protocols for processing B.tabaci captured on yellow sticky traps and for bulking of multiple B.tabaci individuals prior to DNA extraction. This work assembles all of the essential features of a validated and quality-assured diagnostic method for the identification and discrimination of tomato-infecting begomovirus and B.tabaci vector species in Australia. This flexible panel of assays will facilitate improved quarantine, biosecurity and disease-management programmes both in Australia and worldwide.

An unusual combination in papaya ( Carica papaya): the good (glucosinolates) and the bad (cyanogenic glycosides)

Glucosinolates are a group of sulphur-containing glycosides found in the plant order Brassicales which includes the Brassica vegetables such as broccoli, cabbage and cauliflower. When brought into contact with the plant enzymes, myrosinases, the glucosinolates break down releasing glucose and other products which serve principally in plant defence against herbivores. The most important of the products from a human nutritional viewpoint, are the isothiocyanates. These potent inducers of detoxifying enzymes bestow the distinct anti-cancer properties on these plants. Unique among tropical fruits, papaya is known to contain an abundance of one particular glucosinolate, glucotropaeolin. Other compounds that play a pivotal role in the chemical defence system of many plants are the cyanogenic glycosides. Cyanogenic glycosides are activated by plant enzymes in the event of pest attack, releasing the deterrent: toxic hydrogen cyanide. Papaya, in addition to glucosinolates, also contains low levels of cyanogenic glycosides, an unusual occurrence because it was assumed that the two classes of metabolites were mutually exclusive. Studies measuring the levels of both in the edible parts of the papaya fruit and other utilised tissues are discussed and considered in the context of potential human health ramifications. All rights reserved, Elsevier.

IPM in the transgenic era: a review of the challenges from emerging pests in Australian cotton systems

The Cotton Catchment Communities Cooperative Research Centre began during a period of rapid uptake of Bollgard II® cotton, which contains genes to express two Bt proteins that control the primary pests of cotton in Australia, Helicoverpa armigera and H. punctigera. The dramatic uptake of this technology presumably resulted in strong selection pressure for resistance in Helicoverpa spp. against the Bt proteins. The discovery of higher than expected levels of resistance in both species against one of the proteins in Bollgard II® cotton (Cry2Ab) led to significant re-evaluation of the resistance management plan developed for this technology, which was a core area of research for the Cotton CRC. The uptake of Bollgard II® cotton also led to a substantial decline in pesticide applications against Helicoverpa spp. (from 10–14 to 0–3 applications per season). The low spray environment allowed some pests not controlled by the Bt proteins to emerge as more significant pests, especially sucking species such as Creontiades dilutus and Nezara viridula. A range of other minor pests have also sporadically arisen as problems. Lack of knowledge and experience with these pests created uncertainty and encouraged insecticide use, which threatened to undermine the gains made with Bollgard II® cotton. Here we chronicle the achievements of the Cotton CRC in providing the industry with new knowledge and management strategies for these pests.

Can sustainable cotton production systems be developed for tropical northern Australia?

This article reviews research coordinated by the Australian Cotton Cooperative Research Centre (CRC) that investigated production issues for irrigated cotton at five targeted sites in tropical northern Australia, north of 21°S from Broome in Western Australia to the Burdekin in Queensland. The biotic and abiotic issues for cotton production were investigated with the aim of defining the potential limitations and, where appropriate, building a sustainable technical foundation for a future industry if it were to follow. Key lessons from the Cotton CRC research effort were: (1) limitations thought to be associated with cotton production in northern Australia can be overcome by developing a deep understanding of biotic and environmental constraints, then tailoring and validating production practices; and (2) transplanting of southern farming practices without consideration of local pest, soil and climatic factors is unlikely to succeed. Two grower guides were published which synthesised the research for new growers into a rational blueprint for sustainable cotton production in each region. In addition to crop production and environmental impact issues, the project identified the following as key elements needed to establish new cropping regions in tropical Australia: rigorous quantification of suitable land and sustainable water yields; support from governments; a long-term funding model for locally based research; the inclusion of traditional owners; and development of human capacity.

The plasticity of NBS resistance genes in sorghum is driven by multiple evolutionary processes

Background Increased disease resistance is a key target of cereal breeding programs, with disease outbreaks continuing to threaten global food production, particularly in Africa. Of the disease resistance gene families, the nucleotide-binding site plus leucine-rich repeat (NBS-LRR) family is the most prevalent and ancient and is also one of the largest gene families known in plants. The sequence diversity in NBS-encoding genes was explored in sorghum, a critical food staple in Africa, with comparisons to rice and maize and with comparisons to fungal pathogen resistance QTL. Results In sorghum, NBS-encoding genes had significantly higher diversity in comparison to non NBS-encoding genes and were significantly enriched in regions of the genome under purifying and balancing selection, both through domestication and improvement. Ancestral genes, pre-dating species divergence, were more abundant in regions with signatures of selection than in regions not under selection. Sorghum NBS-encoding genes were also significantly enriched in the regions of the genome containing fungal pathogen disease resistance QTL; with the diversity of the NBS-encoding genes influenced by the type of co-locating biotic stress resistance QTL. Conclusions NBS-encoding genes are under strong selection pressure in sorghum, through the contrasting evolutionary processes of purifying and balancing selection. Such contrasting evolutionary processes have impacted ancestral genes more than species-specific genes. Fungal disease resistance hot-spots in the genome, with resistance against multiple pathogens, provides further insight into the mechanisms that cereals use in the “arms race” with rapidly evolving pathogens in addition to providing plant breeders with selection targets for fast-tracking the development of high performing varieties with more durable pathogen resistance.

Developing effective fumigation protocols to manage strongly phosphine-resistant Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae)

BACKGROUND The emergence of high levels of resistance in Cryptolestes ferrugineus (Stephens) in recent years threatens the sustainability of phosphine, a key fumigant used worldwide to disinfest stored grain. We aimed at developing robust fumigation protocols that could be used in a range of practical situations to control this resistant pest. RESULTS Values of the lethal time to kill 99.9% (LT99.9, in days) of mixed-age populations, containing all life stages, of a susceptible and a strongly resistant C. ferrugineus population were established at three phosphine concentrations (1.0, 1.5 and 2.0 mg L−1) and three temperatures (25, 30 and 35 °C). Multiple linear regression analysis revealed that phosphine concentration and temperature both contributed significantly to the LT99.9 of a population (P < 0.003, R2 = 0.92), with concentration being the dominant variable, accounting for 75.9% of the variation. Across all concentrations, LT99.9 of the strongly resistant C. ferrugineus population was longest at the lowest temperature and shortest at the highest temperature. For example, 1.0 mg L−1 of phosphine is required for 20, 15 and 15 days, 1.5 mg L−1 for 12, 11 and 9 days and 2.0 mg L−1 for 10, 7 and 6 days at 25, 30 and 35 °C, respectively, to achieve 99.9% mortality of the strongly resistant C. ferrugineus population. We also observed that phosphine concentration is inversely proportional to fumigation period in regard to the population extinction of this pest. CONCLUSION The fumigation protocols developed in this study will be used in recommending changes to the currently registered rates of phosphine in Australia towards management of strongly resistant C. ferrugineus populations, and can be repeated in any country where this type of resistance appears.