Farm Ireland

Monday 20 November 2017

We still have enough chemical weaponry to control septoria

It's essential to clean and decontaminate your sprayer before the new season
It's essential to clean and decontaminate your sprayer before the new season

Richard Hackett

We are approaching a critical point in the year for all crops, whether winter sown, spring sown or the biggest crop of all in an Irish context, grass. Growth rates achieved in April and May can determine a lot of the outcome of the year.

Temperate crops respond to moderate temperatures, adequate available moisture and high levels of sunlight. Late spring/early summer is when these conditions should be at their most prevalent.

It is our role now to ensure that crops are at their most healthy to maximise the benefit from these hoped for prevailing conditions.

Most of the fertiliser should be applied at this point and any impediments or potential impediments to growth should be addressed. Weeds competing with our crops for this light, nutrients and space should also be well under control. In hotter locations, pests pose the highest risk to growth, but normally in our moist cooler climate the biggest risk to growth rate is fungal disease outbreaks.

Winter wheat in particular is a crop that suffers greatly from fungal diseases that thrive in wet cool conditions. Sometimes, like this year, 'hot weather' diseases like yellow rust rears its head in some varieties to remind us of the range of problems we face.

Nevertheless, wheat enemy number one is still septoria; and such a worthy foe deserves a lot of attention.

There has been a lot of focus given to resistance development of the disease to the available armoury of fungicides we have but a few salient points bear repeating.

Firstly, resistance has been found in fields and efficacy reduction has been noted in situations, but to date the available range of armoury we have is still sufficient to combat the disease.

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Secondly, at commercial level, septoria is not a limiting factor to wheat production. Some day this may not be the case but we still have the tools to control the disease. That is not the case for many aspects of wheat production that have received no attention or specialist conferences.

These include:

  • soil pH
  • soil phosphorus levels
  • soil potassium levels
  • soil compaction
  • poor rotations
  • poor drainage
  • insecure land tenure.

The loss of Isoproturon or IPU will also fundamentally change the way we grow winter wheat and winter barley in order to combat grass weed proliferation.

Revenue losses

These are factors that cost the Irish cereal industry thousands of tonnes of lost production and millions of euro of lost revenue every year, and the solutions don't require new laboratory techniques and EU funding to solve. That's probably why they don't get the attention they deserve.

Thirdly, we currently have available to us five fungicide groups or fungicide families to attack and control the disease. Careful use of the full range of armoury available, in controlled and well planned programmes, should ensure that septoria remains a defeated foe well into the future.

Finally, and most importantly, the returns from winter wheat production are slim to non-existent.

Remember that the primary objective of winter wheat production is to make money, not to control disease.

In many discussions, resistance management has become shorthand for spending more money. This year we have been gifted excellent crops in great condition as we approach the bulking up phase of the production cycle. So far they hold promise of good yields. This is not an excuse for over the top fungicide programmes.

The following steps have controlled septoria for the last 60 years and the disease hasn't yet changed sufficiently to warrant a change away from this approach:

  • Careful variety selection
  • Delaying sowing into the autumn
  • Well planned programmes based on three critical timings
  • Alternating the active ingredients and active ingredients grouping
  • use of multi-site contact fungicides.

The production of any crop is a constant battle with nature. The only inevitability is that nature will overcome our best efforts in the short term or the long term, nature has plenty of time on its side.

Septoria resistance is just one arena that nature is choosing to fight back and all we can do when faced with such odds is to make sure that while we continue with our puny efforts, we make money in the process.

Richard Hackett is an agronomist based in north Co Dublin and is a member of the ITCA and ACA.

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