40 resultados para Sexually transmitted diseases.


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Insect pest diagnostics.

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The aims of this project will provide capacity in virology expertise to help protect Australian cotton from virus diseases including both existing and those that pose significant biosecurity threats. This project will also provide continued capacity in virology to support the cotton industry.

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This project aims to examine the possible impact of Tobacco Streak Virus (TSV) on the Australian cotton industry. TSV is transmitted by thrips, causes a disease which has had a significant impact on grain crops in Central Queensland and a preliminary study in 2007 has shown that cotton is also susceptible to field infection in this region, but many questions remain unanswered. This project aims to: • Determine the impact of TSV in “normal” seasons. • Survey New South Wales and Queensland crops and determine alternative weed and crop hosts. • Assess yield-loss in cotton due to TSV, and factors that lead to systemic infection. • Assess thrips vector species present in cotton • Provide extension material on the impact and management of TSV in cotton

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Root disease causes about $503 million in losses annually to Australia's wheat and barley industries. Because of these large losses and in many cases the difficulty in reducing these losses through breeding or management, root diseases are candidates for solutions through genetic modification (GM). Through an extensive review of the scientific literature and patents, a range of approaches to GM solutions to root diseases are critically discussed. Given the high cost of regulatory approval for GM crops and a complex intellectual property (IP) landscape, it is likely that research in this area will be done in collaboration with international partners.

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Diseases remain a significant impediment to the achievement of maximum yield potential of pulses (chickpea, peanut and mungbean) and sunflowers in the GRDC northern region. This project worked closely with public and private breeding programs to identify sources of resistance to the major diseases of pulses and sunflower that dominate in the region. Through varied surveillance activities, a watching brief on pulse and sunflower diseases was maintained and a timely and appropriate response was made to several significant disease outbreaks. Information on the biology and management of diseases was extended to clients in a wide variety of ways.

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Using caged guava trees in Queensland, Australia, provided with food and oviposition sites, the foraging behaviour of females of the tephritid Bactrocera tryoni was investigated in relation to hunger for protein, the presence or absence of bacteria as a source of protein, the degree of prior experience with host fruit and quality of host fruit for oviposition. One aim was to evaluate whether it is immature or mature B. tryoni females that are responsible for initially inoculating host fruit surfaces with "fruit-fly-type" bacteria, the odour of which is known to attract B. tryoni females. Three-week-old immature females provided with sucrose but deprived of protein from eclosion had a much greater propensity than 3-week-old protein-fed mature females to visit vials containing fruit-fly-type bacteria, irrespective of whether vials were associated with adjacent host fruit or not. In the absence of associated bacteria in vials, immature females had a much lower propensity than mature females to visit host fruit. In the presence of bacteria in vials, however, propensity of immature and mature females to visit fruit was about equal. Mature (but not immature) females were more inclined to visit fruit that ranked higher for oviposition (nectarines) than fruit that ranked lower (sweet oranges). Mature females that attempted oviposition during a single 3-min exposure period to a nectarine prior to release were much more likely to find a nectarine than were mature females naive to fruit or immature females with or without prior contact with fruit. Exposure to a nectarine before release did not affect the propensity of either mature or immature females to alight on an odourless visual model of a nectarine, however. As judged by numbers of leaves visited, protein-deprived immature females were more active than protein-fed mature females, irrespective of the sorts of resources on a tree. It was concluded that: the 1st B. tryoni females to arrive on the fruit of a host tree and therefore inoculate the fruit with fruit-fly-type bacteria were unlikely to be sexually immature, but to be mature as a result of having earlier acquired protein elsewhere; the odour of colonies of fruit-fly-type bacteria when associated with host fruit attracted protein-hungry but not protein-fed females; and the odour of the fruit itself attracted mature females (especially experienced ones) but not immature females.

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In 2011, an outbreak of the quarantine-regulated pathogen Potato spindle tuber viroid (PSTVd) occurred in a commercial glasshouse-grown tomato crop in Queensland, Australia. Phylogenetic studies showed that the genotype of this isolate grouped in a cluster of PSTVd genotypes from tomato and Physalis peruviana, and exhibited an interesting mutation (U257→A) that has previously been linked to lethal symptom expression in tomato. Transmission studies showed that the viroid could be mechanically transmitted from crushed fruit sap, but not from undamaged fruits. A low rate of asymptomatic infection was determined for plants in the affected glasshouse, demonstrating the efficacy of using symptoms to detect PSTVd infections in tomato. No PSTVd infections were detected in solanaceous weeds located outside of the infected glasshouse, excluding them from playing a role in the viroid epidemiology. Monitoring and subsequent testing of new tomato crops grown in the facility demonstrated successful eradication of the pathogen. A trace-back analysis linked the outbreak of PSTVd to an infected imported tomato seed-lot, indicating that PSTVd is transmitted internationally through contaminated seed

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Prochloraz as Sportak at 450 g a.i./L is registered for the control of postharvest diseases in papaya in Australia. A project in far north Queensland in 2011, examined the use patterns of postharvest treatments, evaluated treatment dips and sprays for prochloraz concentrations and evaluated the efficacy of prochloraz at 0, 20, 40, 55 and 70 ml/100 L, fludioxonil as Scholar at 260 ml/100 L and azoxystrobin as Amistar at 50 ml/100 L. Results showed that packing shed use of Sportak varied with recycled and stored solutions showing a depletion of the active ingredient. Measured prochloraz in solution was highly pH dependent with nominal solution values only being measured when the pH was less than 3.0. In the fungicide efficacy trial Sportak at the label rate of 55 ml/100 L provided more effective disease control than fludioxonil and azoxystrobin. The trial also suggested that fruit from older trees showed a high degree of disease incidence relative to fruit from young trees.

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Alternaria leaf blotch and fruit spot of apple caused by Alternaria spp. cause annual losses to the Australian apple industry. Erratic control using protectant fungicides is often experienced and may be due to the lack of understanding of the timing of infection and epidemiology of the diseases. We found that Alternaria leaf blotch infection began about 20 days after bloom (DAB) and the highest disease incidence occurred from 70 to 110 DAB. Alternaria fruit spot infection occurred about 100 DAB in the orchard. Fruit inoculations in planta showed that there was no specific susceptible stage of fruit. Leaves and fruit in the lower canopy of trees showed higher levels of leaf blotch and fruit spot incidence than those in the upper canopy and the incidence of leaf blotch in shoot leaves was higher than in spur leaves. Temperature, relative humidity, and rainfall affected leaf blotch and fruit spot incidence. The gained knowledge on the timing of infection and development of disease may aid in the development of more effective disease management strategies.

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Viruses of the genus Mastrevirus (family Geminiviridae) are transmitted by leafhoppers and infect either mono- or dicotyledonous plants. Here we have determined the full length sequences of 49 dicot-infecting mastrevirus isolates sampled in Australia, Eritrea, India, Iran, Pakistan, Syria, Turkey and Yemen. Comprehensive analysis of all available dicot-infecting mastrevirus sequences showed the diversity of these viruses in Australia to be greater than in the rest of their known range, consistent with earlier studies, and that, in contrast with the situation in monocot-infecting mastreviruses, detected inter-species recombination events outnumbered intra-species recombination events. Consistent with Australia having the greatest diversity of known dicot-infecting mastreviruses phylogeographic analyses indicating the most plausible scheme for the spread of these viruses to their present locations, suggest that most recent common ancestor of these viruses is likely nearer Australia than it is to the other regions investigated.

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Anthracnose and stem end rots are the main postharvest diseases affecting mangoes in Australia and limiting the shelf life of fruits whenever they are not controlled. The management of these diseases has often relied on the use of fungicide applications either as field spray treatments, postharvest dips or both. Because of concerns with continuous fungicide use, other options for the sustainable management of these diseases are needed. Field trials were conducted to assess the efficacy of three plant activators for the control of these diseases over a 2-year period on 20-year old ‘R2E2’ mango trees in north Queensland. The activators evaluated were: Bion, Kasil and Mangocote. The efficacy of these activators was compared with that of a standard industry field spray program using a combination of fungicides, as well as to un¬treated controls. Conditions favoured good development of the target diseases in both years to be able to differentiate treatment effects. Kasil as a drench was as effective as the standard fungicide program on the management of anthracnose and stem end rots. Bion as foliar sprays showed similar efficacy with its effectiveness comparable with the standard spray program. Both activators had significantly less disease incidences when compared with the untreated control. The third activator, Mangocote was not very effective in controlling the target diseases. Its effect was not significantly better than the untreated controls. The results from this 2-year study suggest that plant activators can play an effective role in mango postharvest disease management. Proper timing could reduce the number of fungicide sprays in an integrated disease management program enabling sustainable yields of quality fruits without the continuous concerns of health and environmental risks from continuous reliance on fungicide use.

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The shelf-life of mangoes is limited by two main postharvest diseases when not consistently managed. These are anthracnose ( Colletotrichum gloeosporioides) and stem end rots ( Neofusicoccum parvum). The management of these diseases has often relied mainly on the use of fungicide applications either as field spray treatments and/or postharvest dips. Current postharvest dips are under continuous threats because of health concerns and the maximum residue levels allowed on treated fruit continuous to be reviewed and re-assessed. Research needs to keep up with the rate at which changes are occurring following some of these reviews. The recent withdrawal of carbendazin (Spinflo), as a postharvest dip being used to manage stem end rots necessitated the urgent search for a replacement fungicide to manage this disease. A study was therefore undertaken to compare the efficacy of current and potential products that could be used to fill the gap. The following products were evaluated: Carbendazin (Spinflo), Prochloraz (Sportak), Thiobendazole (TBZ) and Fludioxonil (Scholar). These products were tested both under ambient temperatures and as hot dips to identify one that was most effective. Scholar as a hot dip was the most effective product among the ones compared. It effectively controlled both anthracnose and stem end rots at highly significant levels when compared to the untreated control and even Spinflo which is being replaced. As a cold dip, it had some limited effect on anthracnose but had virtually no effect on stem end rots. Based on its performance in these experiments, the product has been recommended for rates and residue studies so that it can be registered as a hot dip for use in controlling postharvest diseases of mangoes.

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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.

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This chapter provides an in-depth review of important diseases affecting avocado production throughout the world. The importance of understanding the interaction of plant pathogens with their avocado host in order for the development of disease management options is also discussed.