Cereal Diseases, Pests and Stubble
Cereal disease management will requires a greater focus due to recent seasonal conditions and increased stubble loads that will increase the prevalence of diseases. The following diseases and pests are of concern:
Yellow Leaf Spot
Situation: Wheat on Wheat
The disease survives on wheat stubble over summer
Spores are released during the following growing season when humid conditions prevail
Infection occurs on wheat plants when spores are present and the leaves are wet for more than six hours. Infection can occur at any stage of crop development, and can spread over the whole plant
The disease is identified by tan-brown spots, surrounded by a yellow margin. When the spots join the leaf dries out and withers
Significant yield loss can occur from severe infection
Strategies to minimise Yellow Leaf Spot:
– avoiding sowing wheat back into wheat stubbles – selecting a variety with some resistance such as Strzelecki, Sunvex, Ellison or Lincoln – infected stubble removal through burning – foliar fungicides such as Propiconazole (Tilt) can assist to manage disease in the crop, however application timing can be difficult
Take-all
Situation: Wheat on Wheat
The disease infects the root systems of winter cereals
Take-all survives over summer on cereal stubbles and alternate grass hosts such as barley grass, brome grass and silver grass
Disease levels are often higher following warm, wet springs that favour inoculum buildup
Symptoms include blackened root systems, premature haying-off and distinct patches of whiteheads
Strategies to minimise Take-all:
– rotating to non host crops such as canola – ensuring that alternative hosts such as volunteer cereals and grass weeds are controlled – seed dressings such as Jockey ($15/ha) or Impact fertilizer treatment ($5/ha) can be used to suppress the disease in situations where it is anticipated to be a problem. The benefit can be even more significant if Stripe Rust control is also required
Crown Rot
Situation: Wheat on Wheat
The disease affects wheat and barley crops by damaging the crown and lower stems, reducing the uptake of water and nutrients
Crown Rot survives over summer on cereal stubbles and will be present in paddocks as long as the residues remain
Moist conditions early in the growing season favour infection
Symptoms and yield loss are highest in dry springs
Strategies to minimise Crown Rot:
– rotation to non-host crops such as canola – ensuring all cereal residues break down – sowing between previous rows will afford a level of physical separation from the disease – removal of infected stubble through burning
Other diseases of note:
Leaf Scald
Situation: Barley on Barley
The disease survives on barley stubbles over summer
Spores are released during the following growing season and are dispersed by rain splash
Strategies to minimise Scald:
– avoiding sowing barley back into barley stubbles – choosing a variety with some resistance such as Hindmarsh – seed or fertilizer treatments can provide early control and manage inoculum buildup
Net Blotch
Situation: Barley on Barley
The disease has two forms, Spot Form and Net Form
Both forms survive over summer on barley stubble and produce dark brown lesions
Net Form Net Blotch can infect seed
Spore production is favoured by moist conditions and temperatures above 15°C
Strategies to minimise Net Blotch:
– avoiding sowing barley back into barley stubbles – choosing a variety with some resistance such as Hindmarsh – foliar fungicides such as Propiconazole (Tilt) offer some protection, however application timing can be difficult
Pests of note:
Slugs
Situation: emerging crops and pastures adjacent to creeks, roadways, rocky outcrops and pasture paddocks
Bare areas affected by slugs can increase significantly in size within days
Strategies to minimise crop damage:
– removing stubble residues through burning – removal of habitat where possible – baiting with pellets containing Metaldehyde
Mice
Populations supported by high stubble loads and spilt grain
Strategies to minimise crop damage:
– early burning to remove habitat and food source – cultivation to destroy habitat