Push to early sowing could see more crop viruses

Push to early sowing could see more crop viruses because of increased aphid numbers

Cropping
Trial work has found that early sowing can have beneficial impacts on yields but can also lead to an increase in virus-carrying aphids.

Trial work has found that early sowing can have beneficial impacts on yields but can also lead to an increase in virus-carrying aphids.

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Early sowing has been one of the main drivers of increased yield in recent years but it also means a higher risk of crop viruses.

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NICK Poole, managing director of Field Applied Research (FAR) Australia has warned the current trend of sowing earlier may lead to higher virus loads in-crop that will need to be managed.

Mr Poole said the unwanted consequence of starting planting earlier would be higher aphid loads in the autumn combined with greater potential from damage from viruses carried by the aphids.

"At the start of the cropping year given earlier sowing an early break there is going to be more crops for the aphids to live on as the crop is up earlier," Mr Poole said.

"In the late winter and early spring we have already seen evidence of that with high levels of barley yellow dwarf virus (BYDV) in cereal crops," he said.

He said there was a concerning trend towards crops with a greater proportion of erect heads at harvest that appeared to be associated with BYDV.

"The links are not totally clear yet but trials have shown the effect of controlling BYDV is that there is a dramatic reduction in erect heads in certain varieties sown early."

BYDV is problematic for farmers as there is no treatment once the symptoms present in the crop.

The only method of control is to limit the number of aphids spreading the virus.

Mr Poole said this could be done via seed treatments and foliar applied insecticides but there can also be impact on non-target beneficial insect species.

"We need to look for an Integrated Pest Management (IPM) approach not more insecticide," he said.

"With something like the neo-nicotinoid group of products we can see they are under pressure in Europe for regulatory reasons, and there really aren't many other tools in the insecticide arsenal we can use safely to avoid damage to non-target beneficial insects."

He said good paddock hygiene, especially in high rainfall zones more prone to having a green bridge to host aphids over the summer, was critical.

"Keeping paddocks clean and not providing that green bridge is important, given crops are being planted earlier," he said.

"We see the advantages of an early plant and what it can do for yields but we also have to look at the things we need to watch out for to ensure we can keep planting in April successfully."

Mr Poole was encouraged by the recent introduction of BYDV tolerance into the UK wheat cultivar RGT Wolverine ( the first European BYDV resistant cultivar to be released).

He said it was ironic the only other breeding programs to achieve this anywhere else in world were here in Australia, with the cultivar Manning also tolerant to BYDV.

Mr Poole made a plea for breeders to look at the introduction of more BYDV tolerant cultivars since with earlier sowing he saw the importance of this trait increasing.

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