4 September 1998

Dont put the blame on strobs for harvest delay

GROWER concerns that strobilurin fungicides have delayed harvest have been dismissed by cereal specialists and fungicide suppliers, who say the unusual season may be more to blame.

Des Wells of Kineton, Warks, runs his own fungicide trials and echoes a common concern that the new compounds left crops unfit for longer than usual.

"There is no doubt that strobilurins have given a good lift in yield, but the straw has been quite green," he says.

A combination of green straw and ripe grain has been common this harvest, especially in the north, agrees Arable Research Centres director, Mike Carver.

He adds: "I am not sure it is correct to attribute all of the problem to strobilurins. We have to look carefully at whether it is a strange seasonal effect."

Dull weather in June and July as well as strobilurin use, especially at the third spray timing, extended green leaf area in many crops, he notes. "But let us not stick the knife in yet because we have had some encouraging results."

At ADAS Rosemaund in Worcs, there was no apparent delay from using a strob on one of two identical fields of Brigadier, says pathologist David Jones. "One was treated with Landmark, the other with a conventional Opus-based programme, and there was no obvious difference in which was ready first."

Yield and quality in wheat and barley have yet to be assessed, he says, adding: "The jury is still out on whether keeping the crop greener for longer makes any difference."

NIAB work, part-funded by the HGCA grower levy, to see if variety trial fungicide programmes need modifying could help. Results are not yet complete, says pathologist Rosemary Bayles, "but strobs have not presented us with problems".

Heavy yielding crops always take longer to finish, so it is by no means bad news, notes Steve Yates of Zeneca, maker of Amistar (azoxystrobin). Tony Grayburn of BASF, which makes Landmark (kresoxim-methyl + epoxiconazole) adds that last years comments mainly concerned sheltered areas, often near trees. &#42


&#8226 Concern over harvest delay.

&#8226 Partly seasonal effect?

&#8226 Yield and quality benefits so far unclear.

First results in

A strobilurin fungicide has boosted winter barley yield by 7% more than a standard triazole in NIAB evaluation work using 10 varieties at five sites. Two sprays of strobilurin Amistar (azoxystrobin + fenpropimorph) averaged 7.3t/ha (3.0t/acre) compared with 6.8t/ha (2.8t/acre) using full-rate triazole and 6.3t/ha (2.5t/acre) at half rate.