August 23, 2013
With reports of stripe rust in NSW and SA, the Department of Environment and Primary Industries (DEPI) is warning farmers to be vigilant about the fungal disease.
While there hasn’t been the “green bridge” of weeds over the summer, stripe rust spores are wind-blown and can travel long distances.
Stripe rust is easiest to identify in the morning. Examine the leaves, especially the older leaves low in the canopy, and look for yellow stripes of pustules. These pustules are raised above the leaf surface.
Also, watch for hot spots in the crop which are one to 10 meters wide and are generally well developed just before the disease becomes widespread in the crop.
Stripe rust is caused by a fungus dispersed as wind-blown spores which produce new infections.
Conditions suitable for epidemic development occur from April to December in Victoria, and stripe rust can be expected in crops by September in most years.
The fungus requires temperatures of less than 18°C (optimum 6-12°C) with a minimum of three hours of leaf-wetness (for example, dew) for new infections to occur.
Once an infection is established the fungus can survive short periods of temperatures as high as 40°C.
Stripe rust can cause significant loss to wheat yield and grain quality, given appropriate environmental conditions and susceptible varieties.
However, growers have shown that by planning to manage this disease they can effectively minimise its effects.
It is important that growers choose a strategy that is appropriate for their situation, and implement it during the growing season.
This warning follows a call to be on the lookout for a range of diseases because of the damp, winter conditions.
This includes being on the lookout for:
Wheat – yellow leaf spot
Barley – spot form of net blotch (SFNB) and scald.
Faba bean – Cercospora, chocolate spot and ascochyta.
Lentils – Ascochyta (in particular the varieties Flash, Nugget and Nipper) and botrytis.
Vetch – Ascochyta.
Field peas – blackspot and downy mildew.
Chickpeas – Early signs of ascochyta.
Canola – blackleg.
With wet conditions, some farmers may find it hard to get on paddocks for another week or two yet to treat diseases. Once conditions improve it will be important to be ready to act quickly as diseases and crops will both advance quickly when day length and temperatures increase.