8 March 2002

Match product to variety needs

Some say all fungicides do

much the same job, so spray

all wheats with the same

basic mix. But that could

not be further from the truth

as our latest Baseline

Advice article explains

CHOOSING the right fungicide programme wont be easy this year, because much of the UK wheat crop was drilled early and will reach the first pgr and fungicide growth stage within a tight timescale, says Masstock technical manager Clare Bend.

That means prioritising spray applications. Variety and drilling date should be the two main considerations, alongside rotation position and lodging risk.

"There is a greater risk of eyespot with the earliest drillings. Higher spore loadings for foliar diseases, such as mildew and Septoria tritici, are also likely," she says.

But timing must also be correct. "Even last year, when responses to fungicides were small and disease pressure was low, timing was important."

Pre-T1 spray

In high-risk areas, such as the south and west, a pre-T1 spray at GS 29/30 is a must with early drillings, believes Mrs Bend. "The aim with this spray is to get disease progression under control as soon as possible."

Varieties such as Consort, Malacca, Tanker and Savannah will be at risk from Septoria tritici regardless of drilling date. A low rate of epoxiconazole will keep it in check until a more robust treatment can be used at T1.

Mildew is also crucial at this timing. "With a variety such as Claire, we are already seeing signs of eyespot and sharp eyespot, as well as mildew. Mildew resistance to strobilurins is widespread, so opt for quinoxyfen + cyproconazole as a preventive tool. Otherwise you will be chasing the disease all season."

T1 timing

Where Septoria is the main concern, use a strobilurin at T1, advises Mrs Bend. "Our choice will be either trifloxystrobin (as in Twist or Swift) or the new BASF strobilurin pyraclostrobin, both of which should be partnered with a triazole."

If the pre-T1 spray has worked particularly well, or the variety is less Septoria prone, Mantra (kresoxim-methyl + epoxiconazole + fenpropimorph) is a good option. "Its excellent value for money and you get a good dose of epoxiconazole."

Varieties that are less susceptible to the disease, such as Hereward, may need a different approach. "Eyespot is an issue with Hereward, so there is a case for spending your T1 budget on an eyespot product, such as Unix (cyprodinil) and a triazole."

Again, Mantra is an option. "The eyespot threat needs to be assessed on a case-by-case basis. Drilling early increases the risk, as do dense, humid canopies. Wheats drilled in the presence of trash are also on the danger list."

T2 timing

Every variety, regardless of its disease resistance, will benefit from a strobilurin at the flag leaf timing, says Mrs Bend.

"Trials done by Masstock last year confirmed this, even though there was very little disease around. An extra 0.5t/ha yield came from strobilurin use, which was down from the more usual benefit of 0.8t/ha over a triazole. The work also showed that choice of strobilurin was less important than spray timing."

Pyraclostrobin (as in Opera and Tucana) will be a front runner for T2, she believes. "It has curative activity, which is a first for a strobilurin, and good persistency. So growers who suffer weather delays at flag-leaf will be reassured."

She adds that the broad-spectrum disease control offered by pyraclostrobin makes it the right product for disease susceptible varieties and disease-prone regions, such as the south-west.

"But with a variety like Claire, which has good inherent resistance, Septoria should be under control by T2. It may then be worth looking at a cheaper option, like Mantra." &#42

Varietal difference

Be aware of varietal differences when planning disease control strategy, says Bob Mills, technical manager with Banks Cargill Agriculture.

Claire and Option are susceptible to mildew, Access may succumb to rust and Consort and Tanker need good septoria control.

"Eyespot is different. Place in the rotation and drilling date are more important than variety in determining risk."

He agrees that a strobilurin is essential at T2 and adds that strobs with re-distribution within the plant give greater flexibility. "But dont extend the interval between T1 and T2 beyond 35 days."

Feed wheats biggest response to strobs

High yielding feed wheats show the greatest response to strobilurins, while lower yielding breadmaking wheats exhibit little effect year on year, says Velcourt technical director Keith Norman.

"The later the crops are drilled, the lower the response. And the lower the disease pressure, the less they respond to. So crops emerging after late November wont achieve a cost benefit from a strobilurin."

Triazole partners should be matched to the varietys disease susceptibility. Use Folicur (tebuconazole) where rust is a weakness, Alto (cyproconazole) for mildew control and Opus (epoxiconazole) if septoria is a concern, he advises.

1 Drilling date Early-drilled crops will reach first pgr and fungicide timing soon, so prioritise spraying according to variety and drilling date.

2 Timing Correct spray timing is more important than product choice.

3 Pre-T1 A must in the south-west at GS29/30 on mildew and septoria.

4 Mildew Already seen on Claire and Option. Use quinoxyfen for control.

5 Septoria Higher spore loadings on early-drilled crops. Consort, Malacca, Tanker and Savannah are susceptible. Low rate Opus pre-T1 will keep it in check.

6 T1 Opt for pyraclostrobin or trifloxystrobin where septoria is a concern, use Mantra if variety has good septoria resistance.

7 Strobilurins Response seen every year, but will be less on breadmaking and late-drilled crops.

8 Partner triazoles Consider disease pressure and varietal weakness. Folicur, Alto and Opus are preferred.

9 T2 Always use a strobilurin and spray at optimum timing. Pyraclostrobin favoured for disease-prone varieties or where spraying gets delayed.

10 Eyespot Drilling date and rotational position determine risk, not variety.