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Salam M.U.,Bentley Delivery Center | Galloway J.,Center for Cropping Systems | MacLeod W.J.,Bentley Delivery Center | Davidson J.A.,South Australian Research And Development Institute | And 5 more authors.
Australasian Plant Pathology | Year: 2011

A simple model, G1 Blackspot Manager, has been developed to predict the seasonal pattern of release of ascospores in relation to ascochyta blight in field pea. The model considers a combination of two weather factors, daily mean temperature and daily total rainfall, to drive progress of maturity of pseudothecia on infested field pea stubble from past crops. Each day is categorised as suitable or not suitable for continuation of the maturation process. The onset of pseudothecial maturity has been found to take place when approximately ten suitable days have occurred. Following the onset of maturity, ascospore release is triggered when daily rainfall exceeds a threshold. The model was satisfactorily calibrated using three datasets from Western Australia. The calibrated model performed well when independently tested with 21 datasets, 17 from Western Australia and 4 from South Australia. It is concluded that G1 Blackspot Manager model has the potential to be used to formulate sowing guides for field pea in southern Australia that minimise the risk of ascochyta blight. © 2011 Australasian Plant Pathology Society Inc.

French R.J.,Western Australia | Malik R.S.,PMB 50 | Seymour M.,PMB 50
Crop and Pasture Science | Year: 2015

Western Australian grain production is dominated by wheat, but growing wheat continually in unbroken sequences leads to increasing problems with soil nutrient depletion, root and leaf disease build-up, high weed burdens, and possibly other less well-defined production constraints. These can adversely affect both production and grain quality. Including breaks in the crop sequence in the form of break crops, pasture, or fallow can reduce these problems, but these breaks can be expensive to implement, in terms of both direct cost and forgone revenue. It is therefore critical to predict the response of subsequent wheat crops to a break in order to choose crop sequences rationally. We conducted a 4-year experiment at Wongan Hills, Western Australia, evaluating how wheat productivity in a wheat-based cropping sequence is affected by including wheat, barley, lupins, triazine-tolerant and Roundup Ready® canola, oaten hay, volunteer pasture, serradella pasture, and chemical fallow. Wheat yield responded positively to fallow, lupins, oaten hay, volunteer pastures and serradella but not to barley or canola when compared with continuous wheat. Responses depended on seasonal conditions; in a dry year, a very large response occurred after fallow but not after lupin or serradella, whereas in a wetter year, there were large responses after these crops. Fallowing, cutting hay, crop-topping lupins, and spray-topping volunteer and serradella pasture all reduced seedset of annual ryegrass dramatically, and reduced weed competition was a major contributor to the observed break crop responses. Nitrogen fixation by lupins and serradella and water storage by fallow in a dry year were also important, but soilborne diseases did not contribute to wheat yield responses. Some yield responses persisted for at least 3 years, and the contribution of effects of weed competition to yield responses increased over this time. These results emphasise the importance of understanding which productivity constraints are present in a cropping system at a given time when deciding whether a break is necessary and which is the most appropriate break. The results also emphasise the importance of managing the wheat crop after a break to maximise the response and its longevity.

Salam M.U.,Bentley Delivery Center | MacLeod W.J.,Bentley Delivery Center | Pritchard I.,Bentley Delivery Center | Seymour M.,PMB 50 | And 6 more authors.
Australasian Plant Pathology | Year: 2011

G2 Blackspot Manager, the second generation (G2) of Blackspot Manager model, predicts disease severity and yield loss in addition to quantified release of seasonal ascospores in relation to ascochyta blight on field pea. The model predicts the disease severity with respect to the expected exposure of field pea crop to ascospores of D. pinodes, with yield loss subsequently related to the disease severity. Both the relationships were developed using published and unpublished data under southern Australian conditions. The model has been used as a decision support tool for developing a field pea sowing guide considering weather-based disease risk and abiotic risk. This paper presents the field pea sowing guide for South Australia, Victoria and Western Australia for the 2010 season and compares it with 2009. The guide is dynamic as the disease severity changes with seasonal weather conditions and is updated weekly starting around mid-April, being delivered principally via the web ( http://www.agric.wa.gov.au/cropdisease ). The paper also discusses other means of communicating the guide to the stakeholders of southern Australia. © 2011 Australasian Plant Pathology Society Inc.

Malik R.S.,0 Dore St | Seymour M.,PMB 50 | Kirkegaard J.A.,CSIRO | Lawes R.A.,CSIRO | Liebig M.A.,U.S. Department of Agriculture
Crop and Pasture Science | Year: 2015

During the last two decades in Western Australia, the traditional mixed farming system has been increasingly displaced by intensive crop sequences dominated by wheat. Intensive wheat sequences are usually maintained by using suitable breaks, including pasture, fallow, or alternative cereal, oilseed and legume crops, to control weeds and disease, or maintain the supply of nitrogen to crops. New cereal fungicide options may also assist to maintain intensive cereal systems by suppressing soilborne cereal diseases. To guide the successful diversification of intensive cereal systems, we evaluated the effect of a 2-year experimental matrix of 10 different sequence options. Wheat in the sequence was treated with the fluquinconazole fungicide Jockey (wheat+J) to control soilborne pathogens, or with the usual seed dressing of flutriafol fungicide (wheat - J), used for control of bunts and smuts only. The sequences were wheat+J, wheat - J, barley, grain oats, oaten hay, canola, lupin, field pea, oat-vetch green manure, bare fallow) in which all treatment combinations were grown in year 2 following the same 10 treatments in year 1. In year 3, wheat+J was grown across the entire area as the test crop. In year 2, grain yields of all crops were reduced when crops were grown on their own residues, including wheat (22% reduction), canola (46%), lupin (40%) and field pea (51%). Wheat+J significantly outyielded wheat - J by 300kgha-1 in year 1 (14% increase) and 535kgha-1 in year 2 (26% increase). Wheat+J was more responsive to break crops than wheat - J in both year 1 and year 2. Break crops sown in year 1, such as canola, fallow, field pea, lupin and oaten hay, continued to have a positive effect on year 3 wheat+J yields. This study has highlighted the importance of break crops to following cereal crops, and provided an example in which a seed-dressing fungicide fluquinconazole in the presence of low levels of disease consistently improved wheat yields.

Salam M.U.,Bentley Delivery Center | MacLeod W.J.,Bentley Delivery Center | Maling T.,Bentley Delivery Center | Prichard I.,Bentley Delivery Center | And 2 more authors.
Australasian Plant Pathology | Year: 2011

A meta-analysis of severity and yield loss from ascochyta blight (AB) on field pea was performed using 18 field experiments conducted over eight seasons in 13 locations in Western Australia (WA). The severity of AB, across the WA grain-belt, reached its maximum limit (AB severity 5) during mid-April sowing and linearly declined to almost nil by mid-July sowing. Pre-sowing rainfall had a significant effect on AB severity: the more rainfall events that occurred the less was the disease severity. The regional and seasonal difference in the rate of decline of the AB severity (slope of the regression line) with delay in sowing was not significant, whereas the intercepts were largely significant indicating there were differences in the initial AB severity status between the regions and seasons. Fungicide control [Impact® in-furrow (flutriafol) application or fortnightly sprays of Bravo® (chlorothalonil)] did not reduce the disease severity in early sowing (week ending 7 May). The yield loss due to AB was calculated as 10.3% per AB severity unit, indicating that a loss of ≥50% could occur with the highest severity. Magnet showed significantly higher yield loss compared to all other varieties. The differences in yield loss between the five regions were not significant. On the other hand, a dry finishing season resulted in significantly higher yield loss than a wet finishing season. These analyses will help design improved strategies for AB management in field pea in Western Australia. © 2011 Australasian Plant Pathology Society Inc.

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