A leading plant pathologist has urged growers to carefully consider how they sequence or rotate consecutive grain crops to minimise plant diseases resulting from the increased use of pulses and summer crops in rotations.

Grains Research and Development Corporation (GRDC) western panel chairman Peter Roberts has urged Western Australian growers to think particularly carefully about which grain varieties to retain for seeding in 2012.

Wheat yields were generally higher following a range of break crops in Grains Research and Development Corporation (GRDC) funded trials in the higher rainfall area of Katanning.

The GRDC Board is accountable to Australia's grain growers, through the industry peak organisation and to the Commonwealth Parliament, through the Minister for Agriculture, Fisheries and Forestry. The GRDC Board normally has between seven and nine directors.

The Chairman is selected and appointed by the Minister. Mr Keith Perrett was appointed by the Minister on 1 October 2007, and reappointed until 30 September 2013.

The Managing Director is appointed by the Board of the Corporation. The Managing Director is the sole Executive Director and holds office at the Corporation's pleasure. John Harvey was appointed as the GRDC’s Managing Director on 1 March 2011.

Five to seven Directors are appointed by the Minister, on advice from a selection committee selected by the Minister. On 22 November 2011 the Minister announced the appointment of 6 directors, until 30 September 2014.

Cropping research in the Mungindi district has ramped up this winter with the establishment of canola, nitrogen and plant population trials on Andrew Earle’s property, “Bullawarrie”.

• Appropriate crop sequences can make significant contributions to the management of important diseases of the major summer crops in the northern region

• A thorough knowledge of the host range and the biology the major pathogens of summer crops is vital when planning crop sequences

• Crop sequencing is only one component of an integrated disease management plan

• Adopt suitable stubble management strategies

o Pulling and mulching infected cotton stubble and retaining it on the soil surface for at least a month prior to incorporation is the best treatment to reduce in-field Fov spore levels.

• Adopt suitable rotation options

o Bare fallow rotation prior to cotton helps reduce disease severity in the subsequent crop.

o A summer sorghum/maize - fallow-cotton rotation can increase cotton plant survival, reduce disease incidence and increase yields in the 3rd year when compared to continuous cotton.

o Legumes such as soybean and mungbeans increase disease so potentially should be avoided in infected fields.

o When using cereal rotations, burn, bury or bale the cereal residues as soon as possible after harvest.

• Residue and organic matter levels influence field pathogen survival and disease incidence.

o Although there were no differences in latest trials between retaining and incorporating residues in either maize or sorghum, the current practice is to retain residues on the surface.

o Many alternate crops when grown in naturally infested soil are infected by the Fusarium wilt pathogen, with infection limited to lower stem and root tissue in some crops only.

o The use of green manuring crops can increase the Fusarium soil population.

• Grow only the most resistant cotton varieties available (varieties with high F-ranks) in fields known to be infested with Fusarium wilt.

• Sunflowers offer an important break for most common cereal diseases such as crown rot.

• Sunflower rotational fit remains flexible, with 41% of crops sown into a long fallow and 25% sown into a short fallow following a cereal (wheat, barley or sorghum).

• Sunflowers are resistant to both Pratylenchus thornei and neglectus nematodes.

• Nitrogen management can be used to target oil contents. Matching nitrate:water at ratios 0.5–1.0 optimised oil contents above the required industry standard of 40% as well as grain yield.

• Sulphur nutrition needs further investigation; however a positive response to yield was obtained from one preliminary trial.

Take Home Messages
• Plan ahead to ensure the amount of feed grown matches the feed needed.
• Early sowing can increase the production of dry matter but suitable varieties must be sown if there is an intention to take the crop through to grain.
• Generally higher sowing rates result in greater early dry matter production, which commits the crop to grazing, or problems such as lodging may arise.
• Stock must not damage the plants through overgrazing, late grazing (past Z30) or pugging.
• The plants must have sufficient time and nutrition, particularly nitrogen, to ensure recovery and maturity.

Take home messages

• Grass removal in pastures is far more effective than spray topping at reducing soil rhizoctonia inoculum.
• Not controlling volunteer Autumn grasses can lead to severe rhizoctonia build up.
• Low inoculum levels can still lead to high root damage.
• At the Wynarka site this season, early soil disturbance has had greatest impact on disease reduction in the crop.