IT WOULD be reasonable for drought-hit farmers to expect that one small silver lining of the lack of rain would be lower levels of plant disease.
However, in pulse crops a Victorian pulse pathologist said this has not necessarily been the case.
Josh Fanning, whose position is jointly funded by Agriculture Victoria and the Grains Research and Development Corporation (GRDC) said while leaf-borne fungal diseases such as the damaging ascochyta blight, had been less prevalent this year there had been other disease problems, in particular with bacterial blight.
“Bacterial blight in field peas has been really damaging in some parts, it has basically taken all yield away from some crop,” Dr Fanning said.
Speaking at the southern pulse agronomy field day near Horsham earlier in the month, Dr Fanning said the disease had been exacerbated by the run of frosts throughout southern Australia in September.
“The frost causes mechanical damage to the plant, the damage caused by the frost to the leaves allows the bacteria in.”
He said once the bacteria were in the plant it changed the cell structure, meaning that warmer temperatures would freeze the plant.
“There have been a lot of cold nights so this has meant the disease has done a lot of damage in some instances, especially in the Wimmera where there were more cold evenings.”
Dr Fanning warned growers that the disease was seed-borne.
“They need to be careful when sourcing seed for next year as the disease travels on the seed and once the crop is sown there are no real treatments; obviously fungicides do not impact a bacterial infection.”
In terms of other diseases, he said there were reports of soil-borne fungal diseases, such as rhizoctonia, especially in lentils and chickpeas, and pythiums (close relatives to fungi).
“Rhizoctonia impacts water uptake and that doubles the impact of a dry year.”
Ironically there were patches, especially in far western Victoria and eastern South Australia where the normal disease drivers of wet and humid conditions saw problems like phytophthora and ascochyta arise.
“During August, although it was not heavy rain it was constant and the leaf area was kept moist, which is conducive to ascochyta, we saw that in parts of the west Wimmera on unsprayed crops,” Dr Fanning said.