What’s the plan for disease control in 2025?

We are off to a better start this season than last in terms of septoria control in winter wheat and compared to recent years.

We have good crops in fields, the weather has been drier than other years in the winter time and the spring so far has been generally cool and dry, ideal for keeping away disease.

However, we don’t know what the season will bring and septoria control, even in a low-pressure scenario, requires a lot of attention.

Teagasc ran a series of disease and weed control workshops last week in Cork, Meath and Carlow. The Irish Farmers Journal attended the Cork meeting where septoria pressure is among the highest in the country. However, the problem of the moment is yellow rust which is rampant in crops in the north east.

One of the first things pointed out was that disease resistance ratings of varieties can be taken down a point if they were planted early, so crops planted in September and early October with a resistance score of 5 for septoria might revise that down to four for example.

High pressure

Teagasc researcher Steven Kildea observed that high pressure was built up by planting varieties with low resistance to septoria early this season and he added that this dry start to the season was needed to avoid a further build-up of pressure.

His focus was now on the T1 fungicide and how the weather develops in the coming days will impact that application.

Attendees were keen to discuss the benefits of a T0 (T zero) fungicide.

A T0 is something that Teagasc has in their suggested programmes where yellow rust is a problem and in high disease pressure seasons, but does not see benefit from in medium to low-pressure seasons.

Some of the audience claimed, that in the absence of yellow rust, a T0 can help to alleviate pressure and provide some protection to crops in case the T1 timing is not met due to weather for example. That T0 traditionally included chlorothalonil, before the product was banned and this provided good return on investment for many.

Now it generally includes a strobilurin(s) based fungicide and a multisite fungicide like folpet or sulphur. However, folpet should most likely be kept for the T1 and T2 sprays.

Disease control

One member of the trade said that “this is about managing a crop, not about managing disease”, while another said it provides insurance if it rains and leaf 3 cannot be hit at the correct time and that it provides a foundation for good disease control.

However, in this low-pressure season Steven said that while a T0 cannot do any harm, the weather gives you the foundation for the season and that a T0 won’t solve problems that may be faced during the season.

He noted that even if a T0 is applied the T1 should still be applied when leaf 3 has emerged to ensure a robust Septoria control programme.

It was generally agreed that a low-cost T0, when farmers are travelling with cycocel anyway, has an upside and there is no disadvantage to the application. The bottom line has to be if farmers see a cost benefit from its application.

T1 and T2

The same rules as the past few years apply for the T1 and T2 timing. Products should be mixed and alternated so an SDHI and an azole or Inatreq with an azole should be applied at either timing.

Inatreq is rated as the top product in Teagasc star ratings and there was a case made for applying this at T1 in order to get disease control off to the best start, but many will say the best product should be applied at T2.

T3

The T3 spray is noted as a benefit to crops where fusarium is a risk in wet and warm weather at flowering. If fusarium is a risk then it can hit yields badly and a well timed T3 can give significant control, but the window to apply this is very small and really very hard to tell when to apply during flowering to get maximum control.

Label requirement

It should be noted that only one Inatreq-based product can be applied to a crop. This is not a guideline, it is a legal requirement. So, if you apply Univoq or Peacoq at T1 for example then you cannot apply new product Jessico One Jettano, which also contains Inatreq, at T2 or vice versa.

Barley

At present winter barley crops have some disease present with some varieties hit more than others with net blotch for example, particularly in winter barley after spring barley.

The major concern at this workshop was for ramularia. Ramularia requires a healthy, non-stressed plant to be kept at bay and a strong fungicide when the awns are emerging. Wet weather will drive ramularia, but it starts in the seed and can be carried in volunteers.

Guidelines

Teagasc guidelines for Septoria control are outlined in Table 1.

It should be noted that these programmes are guidelines for different scenarios in the season ahead produced by the research and advisory teams. Weather, crop management and varieties will all impact on how different crops need to be treated.

Crops need to be walked throughout the year to see what issues arise and what challenges need to be overcome. These programmes provide a solid base for what to do with crops, but each crop will be different and will need to be managed differently. Applying as close to the timing as possible is important and also being prepared to change products where disease pressure is high or low.

Comment

One thing that wasn’t mentioned at this meeting is the need for a healthy crop. We cannot talk about disease control in isolation. Healthy plants fight disease better.

If a crop does not have a readily available supply of phosphorus or potassium or is deficient in elements like magnesium or manganese then they are more at risk.

Soils with low pH and less available nutrients will be under stress. If a crop is lacking in nutrition it is trying to make up for it in other ways and its immune system can be compromised. If a crop is suffering from Barley Yellow Dwarf Virus or yellow rust it is more susceptible to other diseases. If there is a weed infestation there could be more pressure in the crop.

We cannot rely completely on fungicides for disease control. They are the main tool of control, but as their numbers reduce in the tool box we must make sure all things are equal before the sprayer enters the field. This should improve yields and make the fungicide’s job easier.