Farm Ireland

Friday 28 October 2016

Tillage: Bypassing fungicides in fine weather is a risky strategy

Richard Hackett

Published 08/06/2016 | 02:30

Proper application should ensure you get value for money from your fungicides.
Proper application should ensure you get value for money from your fungicides.

As the country basks in the glorious weather luxuriant crops are the norm as they lap up the sunny weather and utilise the moisture that had plenty of opportunity to build up in the winter and spring.

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As winter barley heads towards grain fill, this weather may well have some long-term benefits in terms of enhanced yield. Even some of the early oats and oilseed rape crops may benefit from the current good weather. Yet it has to be said that cereal crops prefer cooler bright weather for maximum grain fill conditions, rather than the hot bright weather experienced.

For winter wheat and spring sown crops however, it's the weather in late June to mid July that will have a bigger bearing on yield formation than the current weather patterns. However, that is not to suggest that good weather at this time of the year does not have a significant benefit on these crops.

The biggest advantage of warm dry weather comes in terms of disease amelioration as wet weather diseases are the most yield debilitating diseases in cereal production. Whether this lack of disease development can be monetised by reducing fungicide spend on these crops is not a decision to take lightly.

While it is true that if there is no disease present, there is no requirement for curative action from a fungicide, most applications are made on the basis of disease prevention and are applied to prevent disease that may occur three to four weeks after application and indeed for the final application, up to six weeks after application.

So there is a significant gamble when deciding not to spray today as you then must predict what the weather will be in a month or six weeks' time. It could well turn out that leaving out a fungicide spray works for three weeks, but just as the crop begins to mature, the weather breaks and disease runs riot through a crop. At this point in the season, it's too late to take action so the disease has a seriously negative effect on yield.

A more prudent approach may be to maintain planned timings for fungicide applications, but there may well be an opportunity to modify the product mix and savings may be available here, for example use of older chemistry or using less comprehensive product mixes.

However, it is important to maintain cognisance of the risk of development of septoria resistance. The risk of resistance development with this disease is such that each application should have a number of modes of action or fungicide groupings included, but the product may not need to be the latest and greatest combinations.

The fly in the ointment of good weather as mentioned above is that temperate crops like cereals and indeed grass lose too much moisture through their transpiration processes in high temperatures. They have to 'shut down' for most of the day and only actually grow during the shoulders of the day when temperatures are lower and therefore moisture losses are lower.

At this time of the year however, growth during the shoulders of the day is quite enough to meet requirements. Crops designed to grow in higher temperatures, such as maize, can grow all day in high temperatures but don't generally grow as well in the normal temperatures exhibited in a climate such as ours. That's why otherwise unsuitable varieties of maize have to be grown with the quite frankly ludicrous practice of covering with plastic in order to ensure that the crops grow well over a season in such a climate as ours.

I say it's ludicrous as it's my considered opinion that growing maize under plastic in Ireland is a classic case of beating a square peg into a round hole with pure brute force and ignorance, just to prove that it can be done.

The maize has to be forced to grow in such an artificially created climate in order to displace another feed source, mainly grass but also cereals, which naturally grow very well in our climate.

In an era where carbon counting is becoming such a marketing tool for our beef and milk exports, surely the practice of covering the ground with non-renewable oil based plastics, in order to feed cows that could otherwise be fed with grass and home-grown cereals, has to be at least questioned?

Dr Richard Hackett is an Agronomist based in North County Dublin and is a member of the ITCA and ACA

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