Ciaran Collins: Frequent checks essential as winter cereals’ growth rates accelerate

Regular crop inspections are essential for correct input timings as growth accelerates in winter cereals

As we move from late spring into early summer, biomass production in winter cereals accelerates with increasing radiation levels. Management decisions on nutrition, disease control and growth regulation during this phase are critical to final yield.

The foundations for this year’s winter cereal crops were laid last autumn and crops planted into nutrient rich biologically active soils are on solid foundations.

The crops’ ability to produce a high yield is strongly influenced by the cornerstone that is the variety’s resistance to lodging and disease and its yield potential.

Correct input timings are key to success. It is impossible to get the crucial timings on inputs correct without regular visits to the crop as growth speeds up. Fungicide use needs to be targeted.

Applying high rates of broad-spectrum fungicides to cover all bases does nothing for disease resistance, the environment or your pocket.

Regular crop inspections allows us to monitor and target key diseases with the most effective product at an appropriate rate.

Winter wheat

Yellow rust has been evident again this year in susceptible varieties such as Bennington, JB Digeo, Torp and to a lesser extent Graham. We know from our research that the best fungicide timings for septoria control in wheat is when leaf three and leaf one fully emerged, but in the case of yellow rust earlier intervention is warranted if it is present in the crop.

Where rust is active, fungicide application at leaf three should contain a strong rust product like Elatus Era.

We are very fortunate to have new actives in Inatreq and Revysol available to control septoria but we need to be sensible in how we use them. Both are at risk of resistance so we need to manage disease control and resistance together.

Rates should be appropriate to the disease risk and only use as much as is required. The appropriate rate can only be determined by regular crop inspections.

The first part of any resistance strategy is to use a mix of actives so it is essential that the multisite Folpet is included at both leaf three and leaf one applications.

All wheat should have 75% of total nitrogen applied by growth stage 31-32 with the remainder applied before flag leaf.

Winter barley

Winter barley should have received all its nitrogen by now. The recent dry weather has helped to slow the progress of rhynchosporium that was present in some crop a few weeks ago.

Cleaner crops have only recently got their first fungicide and will only require one more at flag leaf to awn emergence.

Where a late tillering fungicide was required, an additional fungicide may be required possibly in conjunction with a growth regulator. Half rates of a mix of actives is sufficient in these cases.

Control of ramularia will be more difficult this season due to the revocation of chlorothalonil. Revysol, Prothioconazole and Folpet all have activity on ramularia but much less than chlorothalonil.

The threat from ramularia is dependent on a number of factors but the inclusion of Folpet at the final fungicide timing will aid control.

Variety lodging rating, nitrogen rate, previous plant growth regulators and crop plant density are all factors in assessment of lodging risk. Walking the crop between growth stage 32 & 39 will help make the decision to apply or not and the rate required.

Winter oats

Final grain numbers is dependent on radiation interception from 20 days before the start of flowering to the end of flowering so it is important to keep the crop free of disease in order to maximise radiation interception during this period.

Fungicide options for winter oats are limited following the withdrawal of Epoxiconazole and Fenpropimorph.

Mixtures of Prothioconazole plus Strobilurins or Elatus era will form the basis for disease control at growth stage 32 and ear emergence.

Teagasc trials found that growth stage 32 is the most effective timing for growth regulation but be careful of late applications. All nitrogen should be applied by growth stage 32.

Ciaran Collins is a Teagasc crops specialist based in Midleton, Co Cork

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