July 30, 2012
Damp weather in the Wimmera and Western District has prompted a warning to croppers to be on the look out for several fungal diseases which are emerging in cereal crops. Department of Primary Industries (DPI) pathologist Dr Mark McLean said he had received several reports of croppers seeing the spot form of net blotch in barley, and yellow leaf spot in wheat crops. The less common net form of net blotch of barley is also likely to be appearing in susceptible varieties. “All three are spread via stubble residue which has been exposed to these diseases in the past two seasons. In addition, damp weather in recent weeks has been ideal for these fungal diseases,” Dr McLean said. “While spot form of net blotch appears to mainly affect grain quality, the less common net form can, in severe cases, cut yield by 20-30 per cent.” The net form of net blotch starts as pinpoint brown lesions, which elongate and produce fine, dark brown streaks along and across the leaf blades, creating a distinctive net-like pattern “For the past two decades the net form has rarely been seen in Victoria because most barley varieties had good resistance to the disease but in recent years some varieties with less resistance have been grown, leading to a higher risk of the disease,” Dr McLean said. “We urge croppers to monitor over coming weeks and if symptoms appear, apply fungicides as necessary. Application of foliar fungicides at around the stem elongation stage (GS31) will provide the best results.” Dr McLean said many wheat varieties did not have good resistance to yellow leaf spot, which initially appears on the wheat leaves as small yellow-brown oval spots. “Often yellow leaf spot is a minor problem for wheat growers but with the current weather conditions there is a risk it could be a bigger issue this year,” he said. “In 2001 when the conditions were ideal for yellow leaf spot, losses of 10-15 per were reported in some susceptible wheat varieties in the Mallee.” Dr McLean urged croppers to keep an eye on their crops in coming weeks and seek advice from their consultants when managing these fungal diseases. . “One easy way to find out disease rating is through DPI’s new Crop Disease Application for smartphones which gives disease ratings and photographic examples of crop diseases,” he said. The easiest way to download the Crop Diseases Application is to press the app store icon on your device and search for crop disease. Then download the free app.