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