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Saturday 22 September 2018

This year's winter cereals are the cleanest I have ever seen

Noreen O'Mahony with Lucy, Fiona and Sheila Ahern and Jaimee Mangan at Clonakilty point to point races. Picture Denis Boyle
PJ Phelan

PJ Phelan

Every year produces new challenges and sometimes opportunities for tillage farmers.

Our wet and cold winter, starting last August and continuing through to early May, resulted in very difficult sowing conditions.

On the plus side, the low temperatures gave very slow disease pressure, resulting in what I consider to be some of the cleanest winter barley crops I have ever seen when it came to the final fungicide.

Winter wheat, now due its flag leaf spray, is generally remarkably clean.

We have very low levels of our normal problem diseases in winter barley -rhyncosporium, mildew and rusts - but we have an increased incidence of leaf blotch caused by Stagonospora nodorum (formerly Septoria nodorum).

This was normally regarded as being of minor interest in barley but this year I have seen up to three and four lesions per leaf.

The lesions are eye-shaped and contain pale brown pycnidia which are difficult to see, even with the use of a lens with its own light source.

The blotching can be confused for net blotch which has a rectangular rather than an eye-shaped symptom and also has a network of darker lines within the lesion.

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Ramularia is also similar in appearance but has rectangular lesions without the netting.

Loose smut is evident in a number of winter barley crops. Such crops and crops of barley in adjoining lands should not be kept for 'home saved' seed.

The economics of 'home saved' seed is questionable but if you are considering doing so you should select the area now, making sure that it is weed-free, disease-free and stress-free; inspect it frequently between now and harvest.

Reject it if it is not up to the standard - as you would expect a Department official to do if it was seed for certification.

Most of our spring crops will have been sprayed by now with an aphicide to prevent transmission of Barley Yellow Dwarf Virus (BYDV).

There may have been justification for some of that spraying this year and in the past but there is no doubt that some and perhaps a lot of that spraying was unnecessary.

Every year I debate the need for spraying and only recommend aphicides where I consider risk is particularly high.

This applies to late sowing combined with sheltered fields/ patchy crops/ presence of aphids and a forecast for little/no rain during the normal spraying period, the three- to five-leaf stage.

There are many fields where no aphicide has been sprayed and where there have been no visible losses from BYDV.

Spraying does kill our natural predators - ladybirds, beetles etc - and leaves crops very exposed to BYDV infection now that resistance by aphids to aphicides is evident and increasing.

Blanket recommendations are not the answer.

We need research to see how BYDV can be managed and perhaps put the pressure back on plant breeders for varietal resistance, on the advisor for a science-based in field assessment. We also need to look at the impact of spraying on non-target (and perhaps beneficial) organisms.

Every farmer and advisor is required to implement Integrated Pest Management, a combination of pesticides and non-pesticide techniques. It is up to research to give us the tools to do so.

The development of disease resistance to pesticides is an ongoing problem. Throughout Europe and in the UK there is a new strain of potato blight (Dark Green 37) which is resistant to fluazinam (Shirlan, Volley, Tizca).

While it has not been identified in Ireland, the fact that blight monitoring in the UK found 3pc of blight sprouts had the infection in 2016 and 24pc in '17, is a cause for real concern.

The loss of fluazinam would have major implications for blight control as it would put increased pressure on other fungicides.

The resistance strategy must consist of a combination of cultural and fungicide usage.

European research has shown that oospores from infected crops can survive for up to four years.

Therefore all crops planted within four years of the previous potato crop are most at risk.

The key cultural controls recommended are:

Maintain longer rotations - no more than one potato crop in five years

Control volunteers in other crops

Prevent foliage growth on outgrade piles

Locate crops away from volunteers or outgrade piles

Use varieties with good blight resistance

Source good quality seed

Ensure that fungicides are selected and rotated based on mode of action - similar to cereals, potato fungicides have different active ingredients with similar modes of action. Include mancozeb or chlorothalonil in every tank mix.

PJ Phelan is a tillage advisor based in Tipperary and is a member of the ACA and ITCA

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