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Crop Crack 11.04.09
By Wendy Fearon
The showery conditions over the last week certainly could not have come at a worse time as many growers prepare to sow. Temperatures are fairly average for the time of year but soils are beginning to warm and with nitrogen applied over the last few weeks, so crops are now starting to grow. The pale yellowing associated with nitrogen deficiency should soon disappear. Trace element deficiencies are showing up widely, mostly Manganese but also Zinc in some cases.
There are two types of lodging; stem-base lodging and brackling. Stem-base lodging is where the plant folds over at the soil surface as a result of poor anchorage in the soil, and is caused by poor root ball development, more likely when the seedling develops in wet soils that limit root development. Brackling is where the stem folds over part way up the plant, and occurs as a result of an inherent weakness of the variety, very dense canopies, and bursts of rapid growth.
Whilst CHLORMEQUAT (3C) will reduce the likelihood of brackling, it will have no effect on root growth; ADJUST on the other hand is active on both types of lodging when applied at the correct timing.
The growth regulator often goes on with a T1 fungicide application sometime around 1st-2nd node, GS31-32. At this timing it primarily stiffens the stem by shortening the internodes, so reducing the likelihood of brackling. However when applied before the end of tillering, GS29, the growth regulator increases root growth also and so reduces stem-base lodging.
Early application of CHLORMEQUAT will not work effectively at temperatures less than 8°C. ADJUST is a more consistent alternative – it will work right down to 1°C. It is also much safer to the crop, particularly when applied in tank-mix with other pesticides.
When applied early it also has a very significant effect on increasing tiller survival so improving yield potential. It is an excellent aid to managing more backward crops when applied at mid-tillering, GS22-24, helping these crops thicken out, an effect not achieved with 3C.
Winter barley
It is now too late to control annual meadow grass in winter barley and crops which have not yet received a herbicide, only the broad leaved weeds can be controlled now. ALLY MAX in a tank mix with a suitable partner should be applied in this case.
Levels of disease are extremely varied at present with crop variety and sowing date playing a big part in this. It is essential to get the T1 application on when the crop has reached first node stage, GS31. Due to the very damaging effects of Rhyncho, delaying beyond this timing will adversely impact on yield and will not be undone by later applications. As well as controlling Eyespot, this treatment will control any Rhyncho and Net Blotch already present and prevent reinfection of the crop as it starts to elongate right up to flag leaf emergence. The addition of chlorothalonil will add to the Rhyncho activity, and provide protection of Ramularia later.
Use flusilazole or epoxiconazole as the base at T1 for good curative and persistency at low cost. Products such as PUNCH C, MIDAS or MANTRA are good choices at this time. TALIUS (proquinazid) is the strongest active on barley and wheat Mildew, lasting up to 2 weeks longer than existing standards. Its inclusion in mixture with other actives also improves the control of other diseases.
Winter wheat
A better option now for well tillered AMG than IPU is the Bayer sulfonyl-urea (SU) actives iodosulfuron & mesosulfuron contained in OTHELLO.Bio Power must be added to Othello at all times. These actives are contact only and therefore need the grass to be completely emerged and growing actively, but are much more effective on larger AMG than IPU. In addition they also have activity on a range of BLWs.Othello may not be applied beyond first node.
The other option is HUSSAR in a tank mix with either hormone or STARANE XL.Hussar requires warm conditions and soil moisture to work effectively and may be used up until 3rd node.
The wheat T1 application should also be applied around the first node stage, GS31. With disease levels currently being low, growers should hold back with this first disease spray until GS31; this will ensure the T2 &T3 timings are that bit later and therefore protection is maintained right to the end of the growing season.
The T1 treatment is targeted to control Eyespot, eradicate any Septoria tritici already present and prevent further re-infection for at least 4 weeks.
Use fluquinconazole as a very cost-effective triazole, or epoxiconazole if more curative activity is required at T1, following up with prothioconazole (PROSARO) at T2. HGCA work still ranks fluquinconazole a very close third just behind epoxiconazole, with prothioconazole a clear leader for Septoria.
Chlorothalonil should be included in all T1 programmes without exception.
I would just like to say there was a printing error on behalf of Farming Life in the last Crop Crack.
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