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Forewarning of ARGT risk for producers

The summary of this study is what now is provided on the DAFWA website, the principal objective of this study (below). Please follow the link provided and click on "ARGT risk forecast 2011." The website appears as follows:

ARGT risk forecast 2011 ARGT is a disease of livestock that results from the consumption of sufficient quantities of toxic ryegrass seedheads. The seed heads are rendered toxic when they are infected by a bacterium, Rathayibacter toxicus, which is introduced into the seedhead by a nematode, Anguina funesta. The disease can arise from the consumption of any feed that contains the toxic seedheads, including pasture, crop stubbles, hay and grain.

For ARGT to occur the toxic bacterium must be present. When it is present the risk of the bacterium building up to levels that are dangerous is principally influenced by weather patterns before and during the growing season. These patterns include false breaks, the incidence and intensity of early rainfall events and temperature patterns. However, the risk can be modified by implementation of pasture and grazing management practices that minimise the production of the toxins that cause ARGT, or by use of the resistant ryegrass Safeguard or the biological control agent twist fungus (Dilophospora alopecuri). There are naturally-occurring populations of twist fungus in some parts of the SW Agricultural region. Conversely, the risk may be increased unintentionally by, for example, causing a pseudo false break as a result of an effective knockdown prior to seeding followed by a second germination event.

More information can be found on the DAFWA website at ARGT. Here, potential risk, assuming the presence of Rathayibacter toxicus and a few mitigating factors, of the incidence of ARGT is predicted using daily weather data from weather stations across the SW Agricultural region each year until July 30. Risk has been predicted as the proportion of properties tested exhibiting ARGT, it does not include an indication of the intensity of R. toxicus on individual properties. Where, all of the precursor elements required for an outbreak of ARGT are present, without any mitigating management practices then the risk prediction will assist producers to assess the management options of their hay crops or pasture, and livestock, to manage the risks of ARGT. Where there is a history of ARGT on a property or in a paddock the predictions here must be treated with caution depending upon management actions that may have unintentionally exacerbated the possible development of ARGT. Equations used to estimate relative risk were developed from information from the export hay industry in the years 2000 to 2005.

Although the hay industry is concerned primarily with levels of the bacterium well below those required to cause clinical disease (the export hay industry works on a virtual nil tolerance for presence of the bacterium), it is expected that the predictions will be equally applicable to farmers considering the risk of ARGT in their pastures, crop stubbles and meadow hay as to export hay producers. For further information contact Dr Jeremy Allen.

This work was supported by the Rural Industries Research and Development Corporation, Meat and Livestock Australia, the Grains Research and Development Corporation and Gilmac Mackie Hay. In this study, a substantial database was used.  It was established in a previous RIRDC-funded project (BSC-1A, Baker and Purser, 2008) and in the 52,561 data fields that were recorded were incidence and severity of R. toxicus in cereal hays for export identified by longitude and latitude of growers paddocks and associated weather information over six years (2000 to 2005).  

In that data base, estimates of date, time and number of false breaks to the season were included.  In this study substantially more data have been added from daily weather data over those six years including estimates of evapotranspiration, soil moisture and an index of greenness.  This large amount of data has been used to predict the risk of incidence of R. toxicus into the future with a reliability of prediction (R2) in the base years, 2000 to 2005, of between 0.53 and 0.70.  This is a reliable estimate given such a large range of weather conditions in those years and hay-producers management decisions during the years of the study.

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This page was last updated on 24/07/2017

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