Battling disease in crops gets harder year on year

THE battle to manage diseases in our key combinable crops gets harder year on year.

We are used to selecting varieties that meet market requirements and promise high yields but as pesticide use comes more and more under scrutiny (and gets more and more expensive) and as we lose actives to resistance problems and regulatory withdrawals, then the use of more resistant varieties becomes more attractive.

Without doubt, some of the issues we currently have with managing high risk diseases like septoria are because we have chased high yield for years and neglected varieties that carried better resistance. This has lead to an over reliance on fungicides.

Septoria, like many pathogens, is pretty smart when it comes to adapting and strains that are insensitive to our main fungicide actives are now endemic.

The better news is that the desire to use more resilient varieties and reduce reliance on pesticides is coming through in wheat, barley and oilseed rape breeding programmes and recommended lists.

Knowing that you have a market for what you produce is a fundamental starting point and each market has preferred varieties although if you decide you are growing for feed your choice is far less restricted.

Yield is important but it not the only criteria – it’s margin that is king not yield.

A variety with a theoretical high yield but key disease weaknesses may rack up fungicide costs and the diseases will quickly erode that upper yield potential.

Whatever the crop and market choice consider what your main disease issues are and include that in your reasoning.

For winter barley, many two-row varieties have weakness to one or more of the major diseases, like mildew, rhynchosporium or net blotch, but some, like the new two-row feed California, have relatively good disease resistance.

Knowing the key disease risks on your farm helps decision-making.

For example, KWS Cassia has good net botch resistance but is relatively weak for rhynchosporium and mildew.

Surge, on the other hand, has better disease ratings across the board but especially for rhynchosporium, net blotch and brown rust.

The list for six-row feed varieties is dominated by hybrids and an example of a new variety with better disease resistance is Funky, which has good all round resistance.

Of the malting varieties, it is important to recognise that some of the market leaders, like SY Venture, have significant disease weaknesses and rhynchosporium can be an issue in this variety.

Encouragingly, there are several new varieties for the soft wheat sector on the list this year (Hardwicke, LG Motown, LG Sundance, Moulton and Savello) which have significant improvements in untreated yield.

For oilseed rape the key foliar disease of concern in Scotland is light leaf spot and there is a minimum rating of 6 for any variety of the recommended list for the north but look for higher than this if you can – the hybrid Alizze, for example, is rated 7 and a conventional example with a 7 rating would be Anastasia.

A final point.

Assessing the key plant health risks you face and using varieties with improved ratings against these is a strong example of integrated practice, so counts towards evidence of an IPM (Integrated Pest Management) plan for the farm as encouraged under the Sustainable Use Directive.

The planning tool for Scottish growers is available here.