Controlling plant diseases without chlorothalonil

From May 20, 2020, the use of chlorothalonil will no longer be permitted here in Ireland. Steven Kildea of Teagasc Oak Park outlined some of the challenges and solutions associated with the loss of the product at last week’s Teagasc National Tillage Conference.

The main diseases which will be affected by this are septoria in wheat, ramularia in barley and chocolate spot in winter beans, while resistance management strategies may also be compromised.

Steven outlined some of the solutions in varieties, agronomy and chemistry.

However, taking septoria as an example, while varietal resistance is improving, plants still need protection. Delaying planting can also reduce the instance of disease, but the costs and benefits need to be weighed up.

Assessing plant nutrition may also help to reduce disease levels.

Steven also noted that fungicides demonstrate an ability to become resistant and chlorothalonil provided a back up when fighting disease.

Steven noted that the same factors affect ramularia in spring barley, but in different ways. He noted that resistance to ramularia does not appear to be available in “elite” varieties and commented that avoiding stress on the plant is important.

The box below outlines Steven’s plan to manage without chlorothalonil.

Know your risk:

  • Strengths and weaknesses of variety;
  • When and where is it being grown?
  • Know the strengths and weaknesses of fungicides.

Know your crop:

  • What growth stage – timings are critical;
  • What is the disease pressure?
  • Is it under stress – ramularia?

Know your fungicide:

  • What can I expect from the fungicide – new or old?
  • Alternative multi-sites do work.

In conclusion, Steven stated that the loss of chlorothalonil will impact disease control, but the impacts can be minimised through varieties, agronomy and chemistry.

He also noted that the need for resistance management will continue and multi-sites are still required.