7 April 2000

Three-way mixes could be best bet

THREE-WAY fungicide mixes could be the most cost-effective this spring, and the most robust resistance strategy.

That was a key message at the HGCAs launch of the new Fungicide Resistance Action Group guidelines for fungicide use earlier this week.

"A multi-mixture approach is the way to go," said British Agrochemical Association representative on the group Andy Selley. "In many ways the more modes of action the better."

Mixing one or more products with two modes of action, such as a triazole and a morpholine, with a strobilurin could both protect the new chemistry from resistance developing, and be the best approach economically, he said.

"There is a lot of the so-called old chemistry that is very good value now, and it is the cocktails that do a better job rather than relying on the straights."

While the FRAG guidelines do not make any recommendation on strobilurin rates, IACR-Long Ashton fungicide specialist Derek Hollomon stressed that growers should use an adequate rate of curative mix according to the disease pressure.

Growers also need to take care not to destroy the effectiveness of a mix by cutting dose too far, he warned. German use of Landmark (epoxiconazole + kresoxim-methyl) was a good example of that. "It was used at 0.25 or 0.5 litres/ha and the epoxiconazole has no benefit for mildew control. Growers need to realise that."

"But the cost / benefit to the grower has to be the driver at the end of the day," added Mr Selley. "If resistance advice does not have the right balance, the grower wont follow the anti-resistance strategy."

FRAG advice, with its focus on UK rather than global agronomic practice, stands more chance of doing that, he believes.

&#8226 11 page FRAG guidelines free from HGCA (020-7420 3920, fax 020-7520 3992, e-mail research@hgca.com or via www.niab.com)

MIXTUREMESSAGES

&#8226 More modes of action the better.

&#8226 Rates should recognise risks.

&#8226 FRAG: UK advice, inc independent sector.

&#8226 FRAC: International, manufacturer driven.