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Stirling G.R.,Biological Crop Protection Pty. Ltd. | Smith M.K.,Maroochy Research Station
Australasian Plant Pathology | Year: 2013

A survey of Fijian ginger farms, and observations of rhizomes received at a processing plant in Suva, indicated that burrowing nematode (Radopholus similis) was responsible for damage to rhizomes and crop losses in two ginger-growing districts, Veikoba and Muanaweni. R. similis was isolated from both small water-soaked lesions and rotted sections of rhizomes, and a pathogenicity experiment revealed that the nematode also invaded the base of shoots, causing collapse and death of plants 20 weeks after inoculation. Symptoms were caused by the nematode alone and not by other ginger pathogens. Observations in the field and results from pot experiments suggested that it should be possible to effectively manage the nematode by rotating ginger with taro and cassava; applying large quantities of poultry manure as fertiliser; and dipping seed in hot water (51 C for 10 min). Since the first two practices are used routinely in the Fijian ginger industry, the reason the nematode continues to cause problems is that many growers fail to ensure that the recommended hot water treatment is applied correctly. © 2013 Australasian Plant Pathology Society Inc.

Stirling G.R.,Biological Crop Protection Pty. Ltd. | Rames E.,Economic Development and Innovation | Stirling A.M.,Biological Crop Protection Pty. Ltd. | Hamill S.,Economic Development and Innovation
Journal of Nematology | Year: 2011

Observations in three Australian sugarcane fields suggested that the soil just under the trash blanket (the covering of crop residue that remains on the soil surface after crops are harvested) was suppressive to plant-parasitic nematodes. Roots were concentrated in this upper layer of soil but plant-parasitic nematode populations were relatively low and roots showed few signs of nematode damage. Root biomass was much lower 15 cm further down the soil profile, where root health was poor and populations of plant-parasitic nematodes were 3-5 times higher than near the soil surface. A bioassay in which Radopholus similis (a nematode that does not occur in sugarcane soils) was inoculated into heat-sterilized and untreated soils, confirmed that biological factors were limiting nematode populations in some of the soils, with soil from 0-2 cm much more suppressive than soil from 15-17 cm. Surface soil from one site was highly suppressive, as only 16% of R. similis recoverable from heated soil were retrieved from this soil after 8 days. Numerous soil chemical, biochemical, and biological properties were measured, and non-linear regression analysis identified two major groups of factors that were significantly associated with suppressiveness. One group reflected the amount of organic matter in soil (total C, total N, and labile C) and the other was associated with the size of the free-living nematode community (total numbers of free-living nematodes, and numbers of plant associates, bacterial feeders, fungal feeders, and carnivores). These results suggested that suppressiveness was biologically mediated and was sustained by C inputs from crop residues and roots. Since nematode-trapping fungi in the test soils could not be quantified using traditional dilution plating methods, their possible role as suppressive agents was assessed by generating TRFLP profiles with Orbiliales-specific primers, and by sequencing cloned PCR products. Although the molecular data were obtained from a limited number of samples, the level of suppression was significandy correlated to the number of Orbiliales clone groups and was also related to the number of Orbiliales species and TRFs, suggesting that this group of fungi may have been one of the suppressive factors operating in the test soils. © The Society of Nematologists 2011.

Stirling G.R.,Biological Crop Protection Pty. Ltd. | Halpin N.V.,Australian Department of Primary Industries and Fisheries | Dougall A.,Maryborough Cane Productivity Services | Bell M.J.,Australian Department of Primary Industries and Fisheries
32nd Annual Conference of the Australian Society of Sugar Cane Technologists 2010, ASSCT 2010 | Year: 2010

LESION nematode (Pratylenchus zeae) occurs in almost every sugarcane field in Queensland and is perhaps the most important of a community of nematode pests that cost the Australian sugar industry an estimated $82 million/annum in lost production. Legumes such as soybean and peanut are relatively poor hosts of the nematode and, when they are used as rotation crops in the sugarcane farming system, populations of P. zeae are markedly reduced. This paper provides data on the host status of other rotation crops that might have a place in the sugarcane farming system, together with some common weeds. The capacity of P. zeae to multiply on various plants was assessed after 70 days in pots at temperatures suitable for nematode reproduction, with multiplication factors calculated as (Pf/Pi), where Pf was the final nematode population density and Pi the initial inoculum density. Sugarcane and forage sorghum had the highest multiplication factors (Pf/Pi >40), whereas the nematode population on most other plants increased 5 to 13 times. Some cultivars of wheat, oats and Rhodes grass had multiplication factors of only 3 or 4 and three crops (Setaria cv. Splenda, barley cv. Grimmett and cowpea cv. Red Caloona) were non-hosts (Pf/Pi <1). In field trials, canola, linseed and chickpea did not increase populations of P. zeae when grown as winter crops at Farnsfield, while wheat and field pea crops grown during winter at Bundaberg did not diminish the level of nematode control obtained from previous crops of peanut or soybean. These results suggest that breaking the sugarcane monoculture with a summer legume followed by a winter crop (e.g. wheat, barley, oats, linseed, canola, field pea or chickpea) will not markedly affect the level of nematode control that is achievable with a legume crop alone.

Giblin-Davis R.M.,University of Florida | Porazinska D.L.,University of Florida | Ye W.,United Road Services | Nobbs J.M.,South Australian Research And Development Institute | And 3 more authors.
Nematology | Year: 2013

Molecular evidence from sequences of three regions of ribosomal DNA (partial SSU, ITS-1, 5.8S and ITS-2, and D2/D3 expansion segments of LSU) is presented to show that the two belonolaimids described from turfgrass in Australia (Ibipora lolii and Morulaimus gigas) are identical. Morulaimus gigas is therefore considered a junior synonym of I. lolii. The decision to place the nematode in Ibipora rather than Morulaimus is supported by molecular studies which showed that I. lolii is not closely related to Morulaimus or Carphodorus, two belonolaimid genera that are only found in Australia. Survey data are presented to show that I. lolii is widespread on turfgrass around Newcastle in New South Wales and in Perth, Western Australia, where the infested area is increasing rapidly, largely because the nematode is being spread in planting material. Ibipora lolii damages all turfgrass species but is particularly damaging to kikuyu grass (Pennisetum clandestinum), the main grass used for sporting fields and recreational areas in warm regions of Australia. Data from an experiment in pots also show that the nematode multiplies to damaging levels on sugarcane. Symptoms on grasses are similar to those caused by the sting nematode, Belonolaimus longicaudatus, in south-eastern USA, but because the two nematodes are taxonomically different, I. lolii is referred to as the southern sting nematode. Ibipora lolii was not found in surveys of natural vegetation on the east and west coasts of Australia, suggesting that it is an introduced species, possibly originating in South America or the Caribbean, where other Ibipora species are found. © 2013 Koninklijke Brill NV, Leiden.

Wong P.T.W.,University of Sydney | Dong C.,University of Sydney | Stirling A.M.,Biological Crop Protection Pty Ltd | Dickinson M.L.,Turf Test
Australasian Plant Pathology | Year: 2012

Two new species of ectotrophic root-infecting fungi pathogenic to warm-season turfgrasses are described. Magnaporthe garrettii P. T.W.Wong & M. L. Dickinson sp. nov. causes a serious patch disease on couch (Cynodon dactylon) bowling greens in South Australia, and Magnaporthe griffinii P. T. W. Wong & A.M. Stirling sp. nov. is associated with a disease complex ("summer decline") of hybrid couch (C. dactylon × C. transvaalensis) golf greens in New South Wales and Queensland. Both are homothallic, producing perithecia readily on potato dextrose agar. They differ from other Magnaporthe spp. in having uniseriate rather than biseriate or multiseriate ascospores, and the absence of a conidial anamorph. Analysis of nuclear rRNA ITS sequences has shown that M. griffinii is a new taxon with low homology to M. grisea, M. poae, M. rhizophila, M. salvinii and Gaeumannomyces graminis. This could not be carried out with M. garrettii because there were no living cultures available and the genomic DNA extracted from dead mycelia and perithecia was totally degraded. However, the two new species can be readily distinguished by morphological differences in their perithecia and ascospores. Examination of earlier herbarium specimens has shown that M. garrettii was associated with a patch disease of buffalo grass (Stenotaphrum secundatum) in New South Wales and M. griffinii was associated with diseases of South African couch grass (C. tranvaalensis) in South Australia and of kikuyu grass (Pennisetum clandestinum) in New South Wales. © 2012 Australasian Plant Pathology Society Inc.

Stirling G.R.,Biological Crop Protection Pty. Ltd. | Smith M.K.,DEEDI | Smith J.P.,DEEDI | Stirling A.M.,Biological Crop Protection Pty. Ltd. | Hamill S.D.,DEEDI
Australasian Plant Pathology | Year: 2012

A field experiment was established in which an amendment of poultry manure and sawdust (200 t/ha) was incorporated into some plots but not others and then a permanent pasture or a sequence of biomass-producing crops was grown with and without tillage, with all biomass being returned to the soil. After 4 years, soil C levels were highest in amended plots, particularly those that had been cropped using minimum tillage, and lowest in nonamended and fallowed plots, regardless of how they had been tilled. When ginger was planted, symphylans caused severe damage to all treatments, indicating that cropping, tillage and organic matter management practices commonly used to improve soil health are not necessarily effective for all crops or soils. During the rotational phase of the experiment, the development of suppressiveness to three key pathogens of ginger was monitored using bioassays. Results for root-knot nematode (Meloidogyne javanica) indicated that for the first 2 years, amended soil was more suppressive than non-amended soil from the same cropping and tillage treatment, whereas under pasture, the amendment only enhanced suppressiveness in the first year. Suppressiveness was generally associated with higher C levels and enhanced biological activity (as measured by the rate of fluorescein diacetate (FDA) hydrolysis and numbers of free-living nematodes). Reduced tillage also enhanced suppressiveness, as gall ratings and egg counts in the second and third years were usually significantly lower in cropped soils under minimum rather than conventional tillage. Additionally, soil that was not disturbed during the process of setting up bioassays was more suppressive than soil which had been gently mixed by hand. Results of bioassays with Fusarium oxysporum f. sp. zingiberi were too inconsistent to draw firm conclusions, but the severity of fusarium yellows was generally higher in fumigated fallow soil than in other treatments, with soil management practices having little impact on disease severity. With regard to Pythium myriotylum, biological factors capable of reducing rhizome rot were present, but were not effective enough to suppress the disease under environmental conditions that were ideal for disease development. © Australasian Plant Pathology Society Inc. 2011.

Stirling G.R.,Biological Crop Protection Pty. Ltd. | Stirling A.M.,Biological Crop Protection Pty. Ltd. | Schmidt S.,University of Queensland | Robinson N.,University of Queensland
37th Annual Conference of the Australian Society of Sugar Cane Technologists, ASSCT 2015 | Year: 2015

A FIELD TRIAL in central Queensland in which high and low rates of N fertiliser (160 and 40 kg N/ha, respectively) had been applied to sugarcane for three years was sampled to assess the impact of N inputs on plant-parasitic nematodes and some of their natural enemies. The soil under five sugarcane accessions was collected immediately after the second ratoon crop was harvested and nematode populations were assessed; nematodetrapping fungi were quantified; and an assay in which the number of Radopholus similis recovered 10 days after being added to heated and unheated soil was used to indicate the level of suppressiveness to plant-parasitic nematodes. Nematode analyses indicated that numbers of lesion nematode (Pratylenchus zeae) and total numbers of plant-parasitic nematodes were significantly higher in the high than the low N treatment. Total numbers of free-living nematodes tended to be lower in the high N treatment and the proportion of bacterial to fungal-feeding nematodes was higher, indicating that with high N, bacteria rather than fungi were the dominant component of the detritus food web. There were also negative effects of N on beneficial omnivorous and predatory nematodes, and a trend towards lower populations of a nematode-trapping fungus (Arthrobotrys thaumasia) with high N inputs. The bioassay with R. similis showed that the level of suppressiveness to the nematode was 39.4% in soil fertilised with 40 kg N/ha and only 18.5% in the 160 kg N/ha treatment, indicating that the soil with higher N inputs was less suppressive to plant-parasitic nematodes than soil from the low N treatment. Collectively, these results indicate that high inputs of N fertiliser are detrimental to some natural enemies of plant-parasitic nematodes. Thus, the fertilisation practices used in sugarcane may be one of the reasons that pest nematodes dominate the nematode community in cane-growing soils.

Manwaring M.,University of The Sunshine Coast | Walter D.,University of The Sunshine Coast | Stirling G.R.,Biological Crop Protection Pty. Ltd.
37th Annual Conference of the Australian Society of Sugar Cane Technologists, ASSCT 2015 | Year: 2015

SOIL MICROARTHROPODS (PRIMARILY springtails and mites) are integral components of the decomposer subsystem, but are essentially unstudied in Australian sugarcane soils. Many of these tiny arthropods are beneficial, as they help regulate the rate of decomposition and nutrient cycling through their feeding processes and by dispersing microbial propagules. Some are also known to feed on nematodes, including those that are significant pests of crops. Herein we review what is known about nematophagous soil microarthropods and present preliminary results from a survey of mineral soil in Queensland cane fields. Densities ranged from 89-529 per 600 mL soil and were dominated by springtails and oribatid mites, indicating a fungus-dominated system. Additionally, about two dozen species of predatory mesostigmatic mites were identified, including many that are known to feed on nematodes. We conclude that sugarcane soils contain a soil microarthropod community with the potential to contribute to the suppression of nematode pests.

Soils from the grain-growing region of northern Australia were assessed for suppressiveness to Pratylenchus thornei by comparing nematode multiplication rates on wheat grown in sterilised soil, non-sterilised soil and sterilised soil to which 10% field soil had been added; or by looking for soils in which the nematode failed to multiply under conditions that favoured nematode multiplication. Bioassays with cropped soils indicated that multiplication of P. thornei consistently increased when soil was sterilised by heat or irradiation, with final population densities in sterilised soil typically 22-35 nematodes/g soil compared with only 2-8 nematodes/g in untreated soil. Soils from native vegetation and pasture reacted in much the same way. Results of other bioassays indicated that multiplication of P. thornei was sometimes reduced by transferring field soil to sterilised soil, and that the nematode failed to multiply in soil from some farms, particularly if that soil was collected from the upper 25 cm of the soil profile. These results suggest that biological mechanisms of suppression are operating in many of these soils. However, shoot growth generally improved when soil was sterilised and so it is also possible that increased root biomass or better root health was partly responsible for differences in nematode multiplication rates between sterilised and non-sterilised soil. Alternative ways of assessing suppressiveness and furthering our understanding of the factors that influence population densities of P. thornei are discussed. © Australasian Plant Pathology Society Inc. 2011.

Vegetable farming systems in tropical and subtropical Australia are vulnerable for several reasons: degradation of the soil resource due to excessive tillage; environmental problems associated with off-site movement of soil, nutrients and pesticides during intense rainfall events; over-reliance on increasingly expensive external inputs (e.g. fossil fuels, plastic film, nutrients and pesticides); and de-registration of the soil fumigants and nematicides normally used to control soilborne pathogens. This two-year experiment compared the performance of a conventional capsicum farming system (an annual forage sorghum rotation crop and normal tillage practices) with three farming systems considered likely to be more sustainable because reduced tillage, a leguminous rotation crop, mulched crop residues and inputs of organic amendments were integrated into the system. One of these alternatives (capsicum grown under minimum tillage in soil mulched with crop residues rather than plastic) yielded significantly less fruit in both years, while root rotting caused by Pythium recalcitrans and Rhizoctonia solani caused problems in all alternative systems in the second year, presumably because the pathogens multiplied on residues from the previous rotation crop. Nevertheless, one of the sustainable alternatives (organic inputs from amendments and direct-drilled rotation crops for 2 years, with plastic laid onto a mulch of crop residues) performed well in all other respects, enhancing suppressiveness to root-knot nematode (Meloidogyne incognita) in the second year and producing higher yields than the conventional system in both years. These results suggest that the conventional vegetable farming system could be improved by 1) incorporating annual applications of commercially-available organic amendments, 2) growing cultivars of forage sorghum and soybean with resistance to root-knot nematode as rotation crops under minimum tillage on permanent beds, 3) mulching biomass from the rotation crops onto the bed surface well before the vegetable crop is to be planted, and 4) leaving the bed undisturbed and covering those residues with plastic. Future research should therefore concentrate on fine-tuning such farming systems; optimising residue management practices to minimise losses from root rotting pathogens that are good competitive saprophytes; and developing mulch-laying equipment capable of laying plastic onto undisturbed beds covered with crop residue. © 2013 Australasian Plant Pathology Society Inc.

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