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Yoga and the art of disease management

Date Added: 02/12/2016

By Richard Elsdon, Technical Consultant, United Oilseeds

Much to my continued bemusement, I am taking yoga lessons twice a week.  Now I thought that yoga involved lying about on a mat and chanting.  Not a bit of it.

Each session begins with breathing while lying on one’s back. But it rapidly becomes more strenuous and entails stretching in some most peculiar ways. The teacher gradually introduced the more complex and demanding exercises by degrees and so subtly, that I did not realise how awkward and demanding the stretching had become. Let me tell you the Pose of Tranquillity takes some doing!

The concept of disease management evolving gradually is common in agriculture.  But I want to concentrate on diseases and, in particular those of oilseed rape. This autumn was warmer than average until late October when it then turned cooler.  During that time, in many areas, rainfall was less than average. In some eastern counties there is still a sizeable moisture deficit.  This lack of moisture does in some way explain the late arrival of Phoma, but it has arrived now and needs treating.

 This is where the difficult decisions begin. Phoma is present now. Light leaf spot (LLS) is out there, or “pending” if you prefer, but so far it has not shown itself as infection on the leaf. It would be a very brave man who decided to ignore the disease on this basis. We know that the incidence of LLS has increased every year and we also know that once established, LLS may die back but, because it is ‘polycyclic,’ it is very likely to return often late in the season when any form of control is both difficult and expensive.

Light Leaf Spot

Like many disease control measures, all action is based on assumptions. I am going to assume that LLS will appear later in the season so where possible, some economy now may well allow a more expensive fungicide later. That could involve for example using tebuconazole or difenoconazole, either in a mixture or as a straight to keep the phoma infection under immediate control. This would save money for a more expensive fungicide when LLS appears. We are told that robust rates of fungicide will be needed to give the best and longest lasting effect on LLS.

When considering the use of a fungicide to control Phoma infection present now, it would be a good idea to check the leaf petioles for the presence of Cabbage Stem flea beetle larvae. The threshold used is that an insecticide should be applied when five larvae can be found. Any insecticide chosen should be compatible with the chosen fungicide. Check any proposed mixture with your agronomist before use.

Autumn diseases, like yoga exercises, tend to build up slowly but there is an element of inevitability about the whole process.  Whilst we have concentrated on Phoma control in the past, the experience of the last two or three years has shown that LLS is in fact the most significant disease. I recommend the first fungicide needs to be relatively cheap leaving money in the bank for Light Leaf Spot control.

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