New strob being tipped on rhyncho and septoria
Fungicides are vital inputs,
but top returns do not
necessarily come from top
rates. In this special,
edited by Andrew Swallow,
we ask where doses can
be cut, passes reduced and
when a robust strategy is
really the best bet. Barley
from the hot-bed of barley
disease, the south west.
Spring barley leaf spotting
is sorted out in Scotland,
and wheat is worked over
by experts in the east.
New triazole metconazole
is profiled, strobilurins
feature throughout, and
Amanda Dunn kicks off
with a north-to-south look
at trifloxystrobin, the
newcomer promised from
TRIFLOXYSTROBIN – the Novartis strobilurin – looks set to find a role on rhynchosporium in the north and septoria in the west, but it is not without limitations, warn agronomists.
"Trifloxystrobin brings rhynchosporium control at a level better than anything we have seen so far," says Jim Rennie, managing director of Crop Chemicals, Scotland.
That view is echoed by Clare Bend, technical manager for Cheltenham-based Masstock group, which has been trialing trifloxystrobin for three years.
"It is definitely the best strobilurin so far for rhynchosporium in barley and in wheat it provides improved control for Septoria tritici. That is the main disease threat facing us in the south west."
Mildew control is better than azoxystrobin, at present, and trifloxystrobin appears to offer more rate flexibility than other strobilurins, potentially making it a more cost-effective choice, she adds.
But the new product is not without limitations. Control of stem-based diseases and rusts is questionable and tank mix restrictions and early access to the product may confine use this season, notes Ms Bend.
"I am yet to be convinced of trifloxystrobins control of yellow or brown rust in wheat, and it is poor on stem based diseases such as eyespot and sharp eyespot. But it is possible to work round these limitations and plug disease weaknesses using triazoles, such as cyproconazole or metconazole for rusts, and cyprodinil for eyespot," she says.
Lack of compatibility data means boosting plant growth regulator activity with adjuvants in tank-mix with trifloxystrobin will not be possible this season, though that may change next season.
For wheat crops, Ms Bend suggests flag leaf as the key timing for this new strobilurin, but Mr Rennie wants to see more work in his area.
"With this type of chemistry you learn once it is out in the field. While it is easy to identify clear targets for barley now, best routes for use on wheat are less obvious."
Rhynchosporium-prone varieties such as Regina, Chariot, Derkado and Optic should be treated at first or second node, possibly with a sec-ond application at flagleaf, he says. "At nodes one and two, control has been achieved with anything from 40-70% of a full dose rate.
"Rate decisions should be based on a combination of what disease you are targeting and how long you are expecting that crop to last, if you go in early use a higher rate, and later use a lower rate.
"To generate a yield kick, an aggregate of 80% of the full dose rate of strobilurin over the season should be applied."
• Rhynchosporium boost on barley.
• Septoria strength for wheat.
• Mildew advantage, for now.
• Weaker on rust and stem-based disease.
Trifloxystrobin has a clear role on winter barley at T1, but more work is needed to see where it will fit for wheat, says East Lothian-based agronomist Jim Rennie. Masstock sees strong septoria and mildew control being an advantage in the west.