Fungicides to fore

Syngenta's Seguris Flexi (isopyrazam) is the only one on the New Zealand market to date but several other manufacturers have SDHI products in the approvals process and deployed in trials.

BASF's is based on the active fluxapyroxad which it has branded as Xemium, though Xemium is not a product name. "It's been in the development pipeline in New Zealand for four years," technical manager Grant Hegarty told Rural News.

Marketed as Adexar in the UK and Europe, it gives broad spectrum disease control in wheat and barley as a foliar spray, and looks particularly promising as a barley seed treatment.

"It would be the only one to offer control of foliar diseases. We're talking about taking out rhyncosporium [with seed treatment] right through to T2."

Meanwhile Bayer's Neil Waddingham was talking about bixafen, another SDHI offering control of all the key cereal diseases, and increasing leaf size. That physiological effect has been shown to increase yield in the absence of disease. "It's the first product [in the UK] to have that on the label."

Such effects could be a key to meeting FAR's objective for wheat yields, 20t/ha by 2020, he believes. "It's a bit more ambitious target than England's 20t by 2032 project!"

Writing in the proceedings provided at the field day, FAR's Nick Poole listed other SDHIs being commercialised globally: penthiopyrad from DuPont; furametpyr from Sumitomo; seed treatment penflufen (as well as bixafen) from Bayer; sedexane (as well as Seguris) from Syngenta.

UK expert Jim Orson noted the SDHI's are "eye-wateringly expensive" but have become the mainstay of wheat T2 sprays in England, with bixafen and fluroxyprazad tending to be preferred to Seguris Flexi as they offer better eradicant activity on speckled leaf blotch (aka septoria).
"But that might not matter over here," he added, in light of the disease's lesser prevalence in New Zealand.

[SECOND STORY]
Accurate grass grub assessement
DO YOU know a first-year grass grub from a second-year specimen? For cropping farmers that's essential to assess the risk posed to autumn planted crops, Agresearch's Richard Townsend told Crops 2012 visitors.

"You really do have to work out if you've got a one-year or two-year lifecycle," he stressed.
Second-year grubs are much larger and pose little risk to autumn sown crops as they wait for winter's cold stimulus to pupate.

In contrast, first-year grubs are smaller but much more active feeders, damaging crops until they reach sufficient size to pupate. As few as 20 such grubs/m2 can cause over 10% yield loss, and even crop failures. "The problem in an arable situation is there's nothing else [other than the crop] for them to eat."

Thresholds in uncultivated ground are considerably higher as grubs are less mobile. "For those of you who can go no-tillage, that's a good option to consider."

To assess populations, use a reasonably small spade to dig out a measured volume of soil, and spread the soil out on a sheet or mat, says Townsend. "Go through it three or four times or you are likely to underestimate the populations."
Grubs from eggs laid this spring will be big enough to get an accurate count by mid to late February.

Chemical control relies on organo-phosphates such as diazinon and phorate but approvals for that group of chemistry are under review by the Environment Protection Authority.

A final decision is expected in July 2013. Meanwhile FAR and Agresearch are investigating use of biocontrols such as Bioshield and yersinia (see opposite) in arable situations.