Farm Ireland

Saturday 20 January 2018

Tough calls to be made on winter wheat fungicide

Summer is here in all its glory as the sight of bees feeding on oilseed rape confirms
Summer is here in all its glory as the sight of bees feeding on oilseed rape confirms

Richard Hackett

The prescription for all crops for the last few months has been heat, moisture and sunlight. These elements finally arrived in a triumvirate over the last week or so, and crops are lapping up these conditions and in general look very well.

The gates are closed on winter barle. It needs to be left to its own devices from now on to soak up the good conditions. Spring crops in general look very well, with thick lush crops, low disease levels and good yield potential being the norm.

The most important issue with these crops, especially where they were sown in a normal winter cereal slot, is whether they will 'die in debt', or will the yield and price cover the cost of production.

The final fungicide on winter wheat is imminent and tough decisions remain to be made.

There have often been question marks over the justification for a final fungicide for septoria control, especially after a disease-free season (to date) and the lower yield potential that current crops have.

Given the general lack of response of fusarium complexes to fungicides, it's hard to justify the spend on that basis either. However, the flag-leaf fungicide application is applied for two to four weeks at this stage and there is another seven weeks of expected growth.

Given the voracity with which septoria can invade a crop, no fungicide programme will last for 12 weeks, and the past few years have shown that late-season septoria attacks can have huge yield and quality effects on crops.

Also, while fungicides can have less than comprehensive fusarium control, they do affect the fusarium complex and any control is better than none.

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In short, a final fungicide around flowering is deemed a necessary part of the crop management programme. The next decision to take is the selection of products. Triazole selection should primarily be based on the triazole used in the previous application, as it is not advisable to use the same active ingredient twice in succession.

The presence or absence of chlorothalonil and strobilurins also warrants discussion. Even the standard inclusion of an aphicide in the final mix is not clear. Many crops have aphids in the ear above threshold levels.

However, the application of non-selective insecticides will affect beneficial organisms as well as aphids. As the insecticide wears off, the aphids can recover faster than the beneficial organisms can, so the balance is skewed in favour of the aphids.

Where action is required on aphids, consider the use of more selective aphicides such as pirimicarb (Aphox) where available, which may alter the balance in favour of the good guys. Where levels are not big, consider leaving the aphid control work to nature.

Potatoes in particular love the warm mild weather and are responding with lush haulm and the promise of good yield potential.

However, another organism that likes warm moist weather is potato blight and robust blight programmes have commenced and must continue on a regular basis from here on in.

There are a range of very effective fungicides available, but do not use any products more than twice in succession, particularly during high blight pressure. Frequency of application, use of a range of products and correct application procedures are more important than any particular product in the control of blight.

When it comes to blight spray application, remember the lessons from last year and have the sprayers, tractors and operators ready for the upcoming war of attrition.

Sprayer booms in particular took a hammering last year with the poor ground conditions.

Weaknesses generally don't fix themselves and it is far cheaper in the long run to have any deficiencies corrected now before the inevitable happens in the middle of a spray round, probably along a narrow road, with crops to spray, weather closing in and parts not available. This is a recipe for stress that may be avoided by giving the sprayer a thorough once over with a critical eye. While sprayers and sprayer repairs are expensive, farmers should bear in mind the cost of the products going through them and the potential losses that may occur should the sprayer fail to operate effectively. With this in mind, let the first cost be the worst cost.

Another important aspect of application is the availability of water. Spend some time planning a spray route that minimises the time spent retracing steps.

Setting up water sources, for example a buffer tank filled with a ballcock at every land parcel, can save many critical spray hours for relatively small cost. As ever, a small amount of time planning can save many hours at critical times.

Dr Richard Hackett is an Agricultural consultant and a member of ACA and ITCA.

Irish Independent