Weather watch guides sclerotinia spraying

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Photo of Derek Ingold

Derek Ingold likes to spray canola to protect it from sclerotinia stem rot on his property near Dirnaseer, 75 kilometres north-east of Wagga Wagga in southern New South Wales.

PHOTO: Nicole Baxter

Derek Ingold considers sclerotinia stem rot to be a yield-robbing fungus worth spraying for, although effective control means keeping a close watch on the weather and subsoil moisture at his mixed farm near Dirnaseer, 75 kilometres north-east of Wagga Wagga in southern New South Wales.

In 2013, this meant carefully monitoring his 400 hectares of canola from the onset of flowering to determine the optimum time to apply fungicide to protect the investment he had made until that point to grow a high-yielding crop.

Although Derek had intended to apply fungicide to protect his canola from sclerotinia at the 20 to 30 per cent flowering stage, he assessed moisture and temperature conditions and considered they were not conducive at that point for the pathogen to germinate and produce spores, reducing the likelihood for infection.

As a consequence, Derek made the decision not to spray, but had pre-purchased enough fungicide to protect the crop should favourable moisture and temperature conditions develop later in the season.

And sure enough, around the 60 per cent flowering stage rain was forecast so Derek booked his contractor and his self-propelled boomspray to apply Prosaro® at 450 millilitres per hectare across the canola.

Derek actually specifies the contractor’s use of a high-clearance, self-propelled boomspray when spraying canola for sclerotinia stem rot because the machinery has the capacity to deliver the high water rates needed (100 litres/ha) to drive the fungicide into the crop canopy and onto the lower stems and leaves.

Following this $40/ha investment, Derek says he was happy with the results. He detected no sclerotinia symptoms in his canola and his entire crop went on to yield 1.95 tonnes/ha on average, a good result given that the farm only received 20 millimetres of spring rain.

Although Derek did not leave any of his canola unsprayed to test the response, other growers in the district who did leave control strips reported the areas that were sprayed with fungicide yielded 200 kilograms/ha more than the unsprayed areas.

Based on this gain and a canola price of $500/t, the net benefit to Derek of spraying his 400ha of canola to protect it from sclerotinia stem rot infection equated to an extra $24,000.

This year, Derek has again budgeted on applying two sprays of fungicide – one at 20 to 30 per cent flowering and another at 60 to 70 per cent flowering. Provided wet and humid weather conditions prevail, yields are estimated to be above 2t/ha and subsoil moisture is high.

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Region South, North