Time to get the fungicides out as the increase in temperature accelerates the spread of septoria

Pat Minnock

Pat Minnock

THE rise in temperature and the excellent growth in the past 10 days has been exactly what crops required.

Crops went from being well ahead of normal early in the season to falling behind over the past month. But now they might be considered to be back at the normal stage for this time of the year.

The flag leaf of winter wheat has emerged and is now due its T2 fungicide. The level of septoria is reasonably high but it has not moved up in crops just yet.

The rise in temperature will increase the spread of septoria and high fungicide rates will be required. Where septoria has moved or is apparent in the higher leaves, a strong eradicant fungicide is required. Adexar, Aviator, Seguris, Gleam or Venture Extra should be the products of choice.

For clean crops these products can also be used but the option to use the older and more competitively priced products containing epoxiconazole and prothioconazole remains. Chlorothalonil at 1L/ha should be included with all combinations and a mildewcide at a half to three quarter rates should be included where there is evidence of mildew or on mildew-prone varieties such as Lion, Cordial, JB Diego and Einstein.

Most crops of winter barley are now eared out and remain relatively clean with only some signs of rhynchosporium. Many crops are sprayed at least four to five weeks at this stage and should now receive a robust fungicide application. This should be at least a two-thirds rate triazole, plus an SDHI, with or without a mildewicide.

Chemicals applied during the very cold spell of early May appear to have caused significant scorch especially on advanced crops of winter oats. Damage was caused to the unfolded flag leaf of the crop.

It appears that the crops most badly damaged were those sprayed when temperatures were at 5-8C which subsequently fell to --3C or --4C. Many growers with three or four-day differences in spraying have found different effects from similar sprays. It is difficult to know what effect this will have on final yield but bad scorch from chemicals/cold spells is never good at this time of year.

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This must be the longest season I have witnessed winter oil-seed rape in flower. What effect this will have on final yields will be interesting considering the level of frost and the length of the cold periods encountered during the flowering period. Final fungicides should now be considered with either 0.5kg Filan, if schlerotina is likely, or 0.7L Amistar plus 0.4L Proline. An insecticide such as Karate could be included for the control of seed weevil.

All early spring barley crops are now at the ideal stage for their T1 fungicide. There is a range of excellent products and combination products available. A full-rate triazole plus or minus a half rate of mildewicide can provide excellent long-term cover. Combination products can provide robust rates of active ingredients at reasonable prices.

All top dressing on spring cereals should be completed at this stage. Late sown crops of spring barley should receive a second aphicide for BYDV control. For malting barley late season nitrogen will improve protein but yield may be affected.

It is now also opportune to target wild oat control in spring barley and wheat. Products such as Axial, Avena, Farmco Axis will do the trick for barley, while these plus Cheetah Extra and Farmco Aphrodite can also be used on wheat. Reduced rates work if applied early.

A vegetable oil should be included for improved control. A T1 fungicide programme for spring wheat should include Chlorothalonil at 1 litre, three quarter rate triazole and a half to three quarter rate of a mildewicide. Finally, 1.5L of CCC should also be included up to growth stage 30-31.

Pat Minnock is a Carlow-based member of the ACA and the ITCA. www.minnockagri.ie

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