You say mesostemic,

4 February 2000

You say mesostemic,

I say quasi-systemic

By Andrew Swallow

ADVERTISING promoting mode of action benefits for Novartiss yet-to-be-approved strobilurin is leading to confusion among growers, claims BASF.

Kresoxim-methyl, the BASF strobilurin in Landmark, Mantra and Ensign, has exactly the same method of movement around the plant as Novartiss trifloxystrobin, claims senior development agronomist, Steve Dennis.

"We applaud the raised profile the advertising is bringing, but it is leading to more of a muddle, more confusion amongst growers."

BASF describes the movement of kresoxim-methyl around the plant as quasi-systemic, a term it has been using since the molecules launch in 1997, he says. "Mesostemic is just another word for the same mode of action."

Both molecules bind onto the waxy surface of the leaf and release vapour. That circulates around and through the leaf, locking onto the waxy layer again to protect both sides, including tissue below the point of application.

Novartis claims that vapour action can control disease on unsprayed plants up to 50cm (20 in) or three rows of wheat away.

Its comment is based on French trials which checked disease levels on unsprayed plants eight weeks after the fungicide had been applied to treated rows with leaf four fully emerged. Thanks to the vapour action Septoria control on leaf two of the unsprayed plants was 68%, says Novartis.

However, the trials data does not include a kresoxim-methyl product for comparison. "We havent compared the two," concedes Novartiss Neil Waddingham.

In contrast to the BASF and Novartis strobilurins, Zenecas azoxystrobin (as in Amistar) is truly systemic, adds Mr Dennis. "It is systemic, and moves around in the manner of a triazole."

However, the kick-back or curative activity of strobilurins on septoria is insufficient to be sure of controlling established disease, hence the need for a triazole tank-mix, he concludes.

&#8226 Novartis does not expect to hear whether trifloxystrobin is approved for use this season until after the Advisory Committee on Pesticides Feb 24 meeting. &#42

QUASI – MESO DEBATE

&#8226 Mesostemic sets trifloxystrobin apart – Novartis.

&#8226 Novartiss "Mesostemic" is nothing new – BASF.

&#8226 Azoxystrobin is systemic – agreed.

&#8226 All primarily protectant.

Mesostemic, quasi-systemic, call it what you like — the fact is that two of the three strobilurin fungicides expected on the market this season do transfer to

adjacent leaves and other plants.

The other product is systemic

anyway.