Varietal resistance important in fight against Ramularia

Ramularia is a common disease of winter and spring barley and up to now has been controlled and prevented by chlorothalonil. Instances of the disease can cause significant yield loss in crops.

Triazoles and SDHIs offer some control, but the removal of chlorothalonil – the main chemical tool used to prevent the disease – from the market has caused concerns for growers.

However, symptoms of the disease only develop after crop flowering – when the final fungicide has already been applied. As a result, a decision support system would be a useful tool to decide on Ramularia risk and to make management decisions.

This was investigated by Teagasc and results of the study were published this week. The study, which investigated ways to predict risk of Ramularia to crops and examine the effectiveness of varietal resistance, used data from field trials from 2016 to 2018.

The field trials examined factors such as year and site (which take weather into account), cultivar (variety) and fungicide treatment.

Previous research has shown that minutes of leaf wetness during stem extension can contribute to the levels of Ramularia in a crop. However, this study only showed evidence of this in four of the six sites/seasons which were investigated.

Of the factors investigated there were interactions between a number, so the study shows the complexity of the disease.

A positive result from the trial was that there were differences in resistance to Ramularia between different varieties, so finding resistant varieties may be a key part of Ramularia control into the future.