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Salam M.U.,Bentley Delivery Center | Galloway J.,Center for Cropping Systems | Diggle A.J.,Bentley Delivery Center | MacLeod W.J.,Bentley Delivery Center | Maling T.,Bentley Delivery Center
Australasian Plant Pathology | Year: 2011

Ascochyta blight is the most destructive foliar pathogen of field peas. The amount of yield loss resulting from the disease in Australia is mainly driven by primary infection from wind-borne ascospores of Didymella pinodes. In this study, a model was developed to predict the spread of ascospores from the ascochyta blight infected field pea stubble of previous season's crops. The model was adapted from a previously developed spatiotemporal model and calibrated with field experimental data consisting of release events of ascospores of D. pinodes from known source for 21 consecutive weeks, under natural environmental conditions, in a 400 m by 400 m area. The model was then applied in a 30.9 km by 36.8 km area in a major field pea growing region of Western Australia to show the magnitude and spatial diversity of the dispersal of ascospores, generated in previous season's field pea stubble, could differ between growing seasons. This simulation was only tested subjectively. It is concluded that a properly validated simulation of this type has potential for understanding the value of physical separation of the current season field pea crop from previous season's stubble, visualising the scale and diversity of ascospore dispersal as an educational tool for growers and consultants, and deriving the "magic figure" of the intensity of field pea area that could result in the presence of ascospores everywhere in a region. © 2011 Australasian Plant Pathology Society Inc.


Borger C.P.D.,Western Research Institute | Hashem A.,Center for Cropping Systems | Powles S.B.,University of Western Australia
Weed Research | Year: 2016

Light is an important resource that crops and weeds compete for and so increased light interception by the crop can be used as a method of weed suppression in cereal crops. This research investigated the impact of altered availability of photosynthetically active radiation (PAR) (from crop row orientation or seeding rate) on the growth and fecundity of Lolium rigidum. Wheat and barley crops were sown in an east-west (EW) or north-south (NS) direction, at a high or low seeding rate, in three field trials in 2010 and 2011 (at Merredin, Wongan Hills and Katanning, Western Australia). The average PAR available to L. rigidum in the inter-row space of EW crops compared with NS crops was 78% to 91% at crop tillering, 39% to 56% at stem elongation, 28% to 53% at boot/anthesis and 41% to 59% at grain fill. Reduced PAR in the EW crop rows resulted in reduced L. rigidum fecundity in five of the six trials (average of 2968 and 5705 L. rigidum seeds m-2 in the EW and NS crops). Availability of PAR was not influenced by seeding rate, but the high seeding rate reduced fecundity in three of the six trials (average of 3354 and 5092 seeds m-2 in the crops with high and low seeding rate). Increased competitive ability of crops (through increased interception of PAR or increased crop density) was highly effective in reducing L. rigidum fecundity and is an environmentally friendly and low cost method of weed suppression. Weed Research © 2016 European Weed Research Society..


Lo-Pelzer E.,French National Institute for Agricultural Research | Aubertot J.N.,French National Institute for Agricultural Research | Bousset L.,French National Institute for Agricultural Research | Salam M.U.,Center for Cropping Systems | Jeuffroy M.H.,French National Institute for Agricultural Research
Field Crops Research | Year: 2010

SIPPOM, a simulator for integrated pathogen population management, has been developed to assess and rank Integrated crop management (ICM) strategies, at the regional scale. The input variables are weather data, soil characteristics, the description of cropping systems (crop sequence and winter oilseed rape crop management) and their spatial distribution, plus the initial size and genetic structure of pathogen populations. Here, we use SIPPOM to simulate phoma stem canker severity, the genetic structure of the pathogen populations, and the yield loss caused by the disease. Sensitivity analysis is conducted to quantify how strongly state variables (sub-model output variables) respond to variations in parameters. The results indicate which parameters need to be more accurately estimated, and it elucidates the steadiness of the rankings of contrasting control strategies under various weather conditions when parameters were varied. Due to the complexity of SIPPOM, the scope of this work was limited to a sensitivity analysis of each sub-model independently. Three values of each parameter were tested under various environmental conditions and crop management according to their expected or known effects on disease and yield. Qualitatively speaking, variations in input variables and parameters provided sub-model output variables that behaved as expected by experts. Parameters with the greatest effect on state variables and that need to be estimated more accurately are for instance those related to pseudothecia maturation and disease severity index estimates. Improvements are foreseen (e.g., the calculation of both the number of phoma leaf spots and the severity disease index). Because the ranking of the simulated control strategies remained steady, despite large variations in the simulated variables linked with variations in parameters, the sensitivity analysis shows that the model, as it stands, can be used to compare and rank ICM strategies with respect to their effectiveness. Possibilities of a sensitivity analysis of the overall model are discussed. © 2010 Elsevier B.V.


Paynter B.H.,Center for Cropping Systems
Weed Technology | Year: 2010

Field studies compared the grain yield of four two-row spring barley cultivars at four sites when sown at two-row spacing in competition with two densities of rigid ryegrass. The sites chosen had low background populations of rigid ryegrass. Although the four cultivars sown differed in their grain yield, row spacing did not influence cultivar performance. Doubling the row spacing decreased barley grain yield at three of the four sites. The impact of row spacing on grain yield was more noticeable when doubled to 48 or 50 cm compared with 36 cm. Rigid ryegrass competition reduced barley grain yield at two of the four sites. At both locations the influence of weed competition on barley grain yield was the same at both narrow and wide row spacing and at one location the impact of weed competition was modified by cultivar. Planting barley in wide rows was found to favor rigid ryegrass production through an increase in both rigid ryegrass biomass production and tiller number. The development of farming systems for barley on the basis of a row spacing greater than 25 cm is likely to be associated with an increase in weed productivity unless good integrated weed management principles are implemented. Modifications to the current system may allow an increase in row spacing without any yield loss or increased weed seed set. Nomenclature: Rigid ryegrass, Lolium rigidum Gaudin LOLRI 'Safeguard'; barley, Hordeum vulgare L. 'Baudin', 'Dash', 'Gairdner', and 'Vlamingh'. © 2010 Weed Science Society of America.


Borger C.P.D.,Western Australian Department of Agriculture and Food | Riethmuller G.P.,Western Australian Department of Agriculture and Food | Hashem A.,Center for Cropping Systems
Crop and Pasture Science | Year: 2010

Enteropogon ramosus is a native, perennial, C4 grass species found within the wheatbelt of Western Australia. Emergence, survival, seed production and seed dormancy of E. ramosus was investigated in a continuous pasture rotation, a pastureminimum tillage wheat rotation, and a pastureminimum tillage wheat rotation where a cultivation event at the beginning of the pasture year was used to kill all E. ramosus plants. The results indicated that E. ramosus could germinate throughout the year, although plant density (ranging annually from 0 to 17plantsm-2) was lowest in conditions of low rainfall (summerautumn drought). Seed production (estimated from seed head production, r≤91.7, P0.001) ranged from 0 to 2274m-2 and was greatest in spring, in the continuous pasture rotation. Seed germinability reached 8089%, following an initial 3 months of dormancy directly after seed production. Cultivation at the beginning of the pasture-crop rotation killed all plants, reduced emergence and prevented seed production for the 2-year period of the experiment. Soil disturbance from minimum tillage crop sowing reduced but did not eliminate E. ramosus plants. As a result, E. ramosus grew throughout the year in the minimum tillage cropping system. Further research is required to determine the competitive effect of E. ramosus on crop growth. © 2010 CSIRO.

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