VIDEO: Yellow rust threat can’t be ignored at T1

Yellow rust may not have made too much impact this spring, but that doesn’t mean it can be ignored in wheat T1 fungicide sprays.

It is just waiting to happen, Andrew Watson, AICC chairman, believes. “And I’ve got a lot of Oakley in the ground, so I cannot afford to take the risk.”

Regular field walking is required until T1 is due on any untreated fields to ensure yellow rust hasn’t struck, he says. “If you see rust, you have to spray.”

About 90% of his clients’ wheat should have received a T0 in early April, weather permitting, even though no active symptoms had been spotted before the end of March. “The main thing was to get some rust protection on for insurance. I also like to get some chlorothalonil on for septoria, although trials suggest there is not a huge benefit from controlling septoria at T0.”

If yellow rust does appear around the time T1 is due, it might change his fungicide choice. “I will change to a high rate of Cherokee (1.5 litres/ha) from epoxiconazole plus Bravo. If the risk is rust I want to get the best product on for that, and hope it gives enough protection [from the high dose of triazole fungicide] for septoria.”

However, where septoria remains the key issue he will stick with Opus + Bravo. “The two best triazoles for septoria are epoxiconazole and prothioconazole. The PSD trials showed that, and whatever Irish and French tests have shown in the lab, field control is fine with them.”

Eyespot is not usually a factor at T1 for him. “If you look at the factors on the HGCA risk assessment tool the main one is second wheats. In Norfolk, we don’t have a lot of second wheats; most wheat follows oilseed rape, roots or peas. Norfolk also has mostly lighter land, is drier and with some later drillings. When I total my risk up it is usually about 20, rather than the 30 you need for high risk. So, should I spend more money on Proline or Tracker for their eyespot activity? Probably not.”

Tim Martin, an AICC-member in Bury St Edmunds, Suffolk, also feels eyespot isn’t an issue. “I believe we have only a handful of crops each year where it is a problem.”

Like Mr Watson, he will be concentrating on yellow rust and septoria at T1. His crops split roughly into two groups – the forward ones, which should have received a T0 with an initial treatment of growth regulator, and more backward ones, where the need for a fungicide will coincide with the T1 timing.

Both sets of crops are likely to receive a similar programme, however, either Opus + Bravo or Cherokee + Proline. The latter will be used particularly where septoria pressure is higher or where rust is present. “The Proline boosts up septoria control, while the Cherokee helps on yellow rust. It gives a nice balance and contains a range of triazole fungicide actives. I’ve had good results with it in the past.”

Disease pressure could be higher earlier this year, he warns. “We’ve had a different year to last. Last year it was dry, this year it is wet. The fertiliser has been washed in, so we’re going to get some lush growth and more disease risk.”

Sprayer calibration and nozzle choice crucial

Make sure your sprayer is calibrated correctly and nozzles are fit for purpose, Syngenta‘s Jonathan Brooks warns.

A worn nozzle could easily apply 5% extra product through a bigger orifice. On a 500ha combinable crops farm, with 50% winter wheat, 150ha oilseed rape and 50ha each of spring beans and barley, the season’s chemical costs could be £64,400, he says.

“So applying 5% more product could mean a £3220 overspend on products. Using a new set of nozzles costing £150-£250 represents good value in that case. It is worth checking.”

Overdosing could also leave areas of fields unsprayed, Mr Watson warns. “About 70% of my applications are calculated for pack size, so if the grower is using worn nozzles he could run out of chemical 100m from the end of the field.”

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