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Resource to Help Growers Manage Yellow Spot

31 August 2011

AUSTRALIA - Help is available for Western Australian wheat growers looking to reduce the risk of yield losses caused by yellow spot, which is currently affecting some of the State's crops.

The Grains Research and Development Corporation (GRDC) has released a new Yellow Spot Fact Sheet outlining management practices to combat the fungal disease, also known as yellow leaf spot and tan spot.

Yellow spot, caused by the fungus Pyrenophora tritici-repentis, is a damaging stubble-borne disease of wheat.

Image 1: Yellow spot causes tan-coloured lesions on the leaves that are surrounded by yellow halos. Where these lesions occur near the leaf tip, the end of the leaf rapidly turns yellow (chlorosis) and dies back.

GRDC supported trials in WA have shown the disease can cause up to 20 per cent yield reductions in very susceptible varieties infected by the disease.

GRDC crop protection manager Rohan Rainbow said the Yellow Spot Fact Sheet included timely advice on fungicide use.

“Fungicides can provide up to three weeks of protection against yellow spot but the economics of fungicide control will depend on the timing of disease development and if moist conditions persist in spring,” he said.

Dr Rainbow said the main factors which increased the risk of yellow spot were farm practices such as minimum tillage, stubble retention, wheat-after-wheat crop sequences and growing susceptible wheat varieties.

“In most instances, a one-year rotation out of wheat is highly effective in reducing early disease occurrence,” he said.

“In addition, any practice that reduces stubble density on the surface will reduce the level of inoculum which causes the disease.

“If wheat-on-wheat must be grown, it is best to avoid seeding varieties that are rated susceptible (S); susceptible to very susceptible (S-VS); or very susceptible (VS).”

TheCropSite News Desk

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