A fungicide formula for keeping costs down

Ramularia control
Ramularia control

Shay Phelan

As spring barley is still the largest single arable crop grown in Ireland, maximising its yield potential will have a significant impact on profitability on most tillage farms again this year.

So far plants have established well and for the most part they have met various targets in terms of plants established, tiller numbers and then, hopefully, ear numbers.

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All the various treatments in terms of nutrition, herbicides and fungicides have all been applied for the most part on time.

So as we approach the ear emergence phase, all the ingredients are in place to maximise the potential of the crop.

The final piece of the jigsaw is the final fungicide application.

The final fungicide application on spring barley is designed to protect the crop from key diseases such as rynchosporium, net blotch and ramularia.

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It builds on the previous application which should have been applied at late tillering which protects the tillers in order to maximise their numbers.

The final fungicide, however, has a different focus as it aims to keep the upper canopy, including the awns, as clean as possible from disease to maximise the amount of light interception by the leaves, which in turn will help to fill the grains.

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When it comes to choosing what chemistry to use there are a number of considerations that must be taken into account.

Firstly, you have to look at which diseases are prevalent in the particular varieties on the farm.

Then choose a chemical that has a good rating for that disease and then apply it at the appropriate rate.

For both rynchosporium and net blotch we have plenty of options to control them. For both of these diseases growers would normally use mixtures that include a triazole and SDHI or Strobulurin chemistry.

The good news from a grower's point of view is that, from Teagasc trial work carried out over a number of years, it has been found that approximately 50pc of the recommended rates of these products will give adequate control, so it is an opportunity to keep costs down.

Growers should, however, avoid using single active ingredients (e.g. a triazole) on its own and always use multiple actives to help to prevent the onset of resistance to the chemistry.

Ramularia (pictured) control, however, is slightly different in that the triazoles, SDHI's and Strobulurins are not very effective at controlling it.

It is a stress related disease which can be difficult to predict and practically all varieties are affected by it to some degree.

At the moment the only product that gives control is chlorothalonil which has recently had its licence withdrawn. However, it is available for the current season.

Unlike the other diseases it will take a full rate of the product, normally 1.0 litre per hectare, to control it. So, unfortunately, there is no chance of making savings here. Timing of the final fungicide is often a hot topic for debate in many discussion groups and farm meetings.

Again, Teagasc has conducted timing trials looking at various timing of fungicides to see which give the best return and the biggest yield response.

Over a number of years, Teagasc has found that applying the final fungicide at growth stage 49 as the awns are appearing (pictured right), rather than waiting until the heads have fully emerged at growth stage 59, will increase yield from this application by on average 0.4t/ha. What this clearly shows is waiting that extra two weeks for the heads to fully emerge is allowing diseases to infect the awns and upper leaves, this infection is then reducing the crop's capacity to carry out photosynthesis which in turn fills the grain. At current prices waiting for the heads to come out fully before applying the fungicide could cost in the region of €55-60 per hectare in lost yield.

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