27 March 1998

Squeezing the best out of

new spray…

Season-long mildew control

is the claim for new

mildewicide Fortress. If you

are persuaded by the sales

pitch, how can you then

make the most of this new

fungicide on your farm?

MAKE sure it is applied early enough and remember its sole target is mildew. Users say those are the key points to bear in mind with quinoxyfen, Dow Agrosciences new wheat and barley fungicide test marketed on about 50,000ha (120,000 acres) last season.

As an alternative to morpholine mildewicides like fenpropimorph and fenpropidin, quinoxyfen offers much longer disease control. But while it is systemic it does not kill established mildew. So ideally it needs to be on before there is more than 5% mildew on new growth, says Dow.

Unlike morpholines, triazoles and strobilurins it controls no other diseases. "It is unlikely to be used on its own," says Dick Neale, trials officer for &#42 L Hutchinson.

Quinoxyfen should prove especially useful where mildew is always troublesome, he says. "Growers on black fen, in Kents wooded valleys, and on Norfolks light manganese deficient soils know they are going to get mildew. This is the product for them."

Many crops are over-thick and recent conditions have been ideal for the disease, he notes.

Despite advice to get quinoxyfen on early, all is not lost if treatment is delayed beyond stem extension (GS31), provided the upper three leaves can be kept clean, says Dows Mike Ashworth. But that will entail adding curative fungicides and the full yield benefits may be lost, warns Mr Neale.

"If there is more than 5% mildew in the crop a knockdown product like a morpholine at a quarter rate should be added. Alternatively, if you are going for septoria and rusts as well then you should mix in a triazole like cyproconazole."

Quinoxyfen dosing is very flexible, but few growers are likely to need the full 0.3litres/ha, suggests David Wall of Herefordshire-based Leadon Vale (Crop Management).

"As far as I am concerned it exceeded all expectations last year. In barley 0.3 litres would keep the crop clean until Christmas. In wheat I see a place for it to bolster the newer kresoxym-methyl, which is perhaps not quite so good on mildew. I have a feeling it is going to be a mildew year."

The key to using quinoxyfen is to get it on early enough to avoid plants having to waste yield-building energy defending themselves, he explains.

Depending on disease pressure and varietal susceptibility quite low rates split along with early growth regulators can effectively protect new foliage, says Peter Cowlrick of Chichester Crop Consultancy.

His own trials and commercial experience last season showed good results from a total dose of as little as 0.15 litres/ha, he says.

"In very high mildew situations you may need a morpholine to pep it up, say 0.2 litres of fenpropidin or 0.25 litres of fenpropimorph."

A key feature of morpholines not displayed by quinoxyfen is their cosmetic effect in browning off mildew pustules. First-time users should not be surprised if they can still find evidence of mildew four weeks after an application of quinoxyfen, he notes.

Although variety resistance ratings can guide quinoxyfen dose rates, they have their limitations, because of differences in mildew tolerance, suggests Mr Cowlrick. "Varieties, like Spark, that you wouldnt think would be very responsive have certainly given some reasonable responses."

Adding adjuvants is unlikely to bring extra benefits or permit big dose cuts, he suggests. And all the evidence is that water volumes lower than the quinoxyfen label recommendation of 200 litres/ha should have no detrimental effect, adds Mr Neale.

Philip Ranby, AICC member in Lincs, reinforces advice to get the fungicide on early after using a small quantity last year. "It needs to be on prior to serious mildew activity," he says. "It is only protectant.

"There is some mildew about and probably worst in Madrigal. But its perhaps not as bad as it looked as though it might have been a while back."

Quinoxyfen may figure in his programmes again this season, but the arrival of the kresoxim-methyl products puts a different perspective on the decision-making, he says. "And personally where there is brown rust I would still think morpholines."

USING QUINOXYFEN

&#8226 Early application needed as protectant only.

&#8226 Adjust dose to risk – 0.1 litres/ha should protect for six weeks.

&#8226 Variety resistance helps decide rate, but not sole factor.

&#8226 Add knockdown fungicide where mildew above 5% on new growth.

&#8226 Water volume not critical but aim for good crop coverage.

&#8226 Adjuvants unlikely to be required.

&#8226 Note: No noticeable mildew browning as with morpholines.

QUIN0XYFENFACTS

&#8226 Products: Fortress & Apres

(also with fenpropimorph as Orka).

&#8226 Formulation: 500g/litre quinoxyfen.

&#8226 Crops: All varieties wheat & barley.

&#8226 Pack size: Fortress 1litre; Apres 0.5 litres.

&#8226 Price:£100/litre

&#8226 Label dose: 0.3litres/ha adjusted to risk, may be split as 2 x 0.15 litres/ha.

&#8226 Water volume: 200 litres/ha.

&#8226 Compatible with wide range of fungicides.

&#8226 Timing: GS25-49.

&#8226 Best results before 5% mildew on new growth.

&#8226 Brewing, Licensing and Retail Association accepted.