Barley yellow dwarf virus (BYDV) tolerant winter barley varieties act as “risk reducers, not risk eliminators”, according to Louise McNamara of Teagasc.

Louise noted that integrated pest management (IPM) measures, like delayed sowing, are still required where these varieties are grown to keep BYDV in check.

With 83% of the Irish winter barley seed area dedicated to varieties with BYDV tolerance or resistance in 2026, this is sound and timely advice for tillage farmers.

Louise has data from six different early-planted winter barley trials over the course of four years. Overall, the results showed that while an aphicide application reduced the amount of BYDV symptoms in both susceptible and tolerant varieties, there were a lot less symptoms to start with in the tolerant varieties.

When it comes to yield, three scenarios were examined. In a low-pressure BYDV year, there was no difference between susceptible and tolerant varieties, or barley sprayed with an aphicide or not sprayed.

In a medium-pressure year, there was a significant difference in yield between sprayed and unsprayed susceptible varieties. The tolerant varieties had a higher yield overall and there was a slight increase in yield when these varieties were sprayed.

A similar trend emerged in a high-pressure year. Aphicide applications increased susceptible variety yield, while tolerant varieties saw a lower yield increase from these applications.

“The tolerant varieties reduced BYDV symptoms and associated yield losses,” Louise explained. While the susceptible varieties experienced a significant yield loss in four of the six trials, this was reduced to two with the tolerant varieties.

Integrated Pest Management

Louise noted that farmers should still consider IPM actions other than just planting BYDV tolerant varieties.

“It is only one tool. If you rely exclusively on one tool, eventually the pest or disease will overcome it like what has happened with some of the sprays,” she commented.

Therefore, practices such as delayed drilling and managing the green bridge from one crop to the next, ensuring there is a six-week clean break, should still be practised no matter what variety is drilled.