Time to apply the T1 to winter wheat
Tuesday April 22 2008
The first of May is looming towards the end of next week and it seems to me that winter just doesn't know when to call it a day and retreat for another year. The cold north and easterly winds seem to have been around since February. Despite cold air temperatures, soil temperatures are close to normal for the time of year and winter crops are responding to the long daylight.
Spring crops are struggling a little more and all growers should keep an eye out for soil pests, such as leatherjackets and slugs. Watch fields with a history of pest damage.
Looking at crops across the country last week, it appears that leaf three is appearing or fully expanded in crops of wheat sown before mid-October. September-sown crops are more advanced. Early developing crops, such as Timber or Cordial, sown towards late October, are also reaching this stage. This week is the ideal week to apply the first main fungicide (T1) to winter wheat.
Many, if all, of these crops have received a T0 fungicide already. If a crop has received no fungicide to date, then it should receive the T1 as soon as possible, where the crop has leaf three fully expanded (where you can see leaf two just peeping out).
During my tour around the country last week, what struck me was a general lack of septoria lesions on the upper leaves of wheat. The only wheat variety which has plenty of disease was Consort, but this is to be expected. However, don't be fooled into thinking that there is no disease in cleaner varieties, as normally there is plenty of septoria at the base of the crop just waiting for its chance to spread upwards.
Mildew
Mildew was absent and I failed, in as far as I can remember, to spot a crop with any level of the disease. However, I did spot eyespot on my travels and, if it is present on your crop, then it should be addressed with the T1 fungicide.
The choice of fungicide for T1 will depend on where the crop is in the rotation. Eyespot will not be a problem in wheats sown into ley fields and a straight triazole will suffice. A 75-100pc rate of Opus is probably best placed to fulfil this timing. However, Proline will perform well, though at a higher cost.
Where eyespot is a concern in continuous tillage, Venture, Proline or Tocata, among others, will control septoria and eyespot. Rates will vary, but at least an 80pc rate should be used. Tocata has the advantage of having a substantial quantity of in-built active ingredient to control mildew. There are many other fungicide options available at T1 that can be used effectively and represent value for money.
Overall, in all the trials I have seen, the inclusion of chlorothalonil (Bravo) will increase yield and is worthwhile at the T1 timing. Legally, you can only apply a maximum of two applications of straight chlorothalonil to a crop. Therefore, if you have applied chlorothalonil at the T0 and also at the T1 timings, you cannot legally apply it again at the T2 stage (in a straight form).
Take-all
Wheats in a rotational position that are susceptible to Take-all (second wheats after a break crop, or third wheats after ley) may require attention now. If you used Latitude dressed seed and applied extra nitrogen at the first nitrogen application timing, you have done all you can for now.
However, if the crop was sown without Latitude, an application of Amistar can help to reduce the take-all level. Yield responses from 0.3t/ha to over 1.0t/ha have been observed in trials (although the smaller responses were gained from trails in Teagasc, Oak Park). It is best to apply Amistar at an early stage. Rates of between 0.6-0.8l/ha should be applied with the T1.
Teagasc crop walks take place in Clonmel today (10.30am) and Midleton tonight (6.30pm) and in Wexford (Ferns, Newross and Crossabeg) and Ballyhooly tomorrow at various times. Contact your local Teagasc office for further details.
All are welcome.
- Michael Hennessy
