Crops Specialist at Teagasc, Ciaran Collins looks at the BYDV risks, sharing key tips on crop assessment and the control options available.
Findings from recent Teagasc experiments on early planting of winter barley indicate that:
- Early sowing increases barley yellow dwarf virus (BYDV) risk,
- Later sowing gives a similar or better yield than early sowing where BYDV is a risk, and,
- A tolerant variety reduces the risk of yield loss to BYDV when sown early where BYDV is present.
Other important factors to consider when assessing BYDV risk are mild weather and whether a ‘green bridge’ is present or not, as volunteer cereals and grasses are host species for the grain aphid. This has been an issue for some growers who had short-term cover crops planted ahead of winter barley this season.
Insecticide application should be targeted. Cereal crops emerging in November are at a much lower risk of BYDV than crops that emerged in October. Check if aphids are present in the crop. Look at the headlands, because aphids are three times more likely to land near headlands than further out in the field. If aphids are present, apply an insecticide at the 2-3 leaf stage of the crop (Table 1).
Table 1: BYDV risk and control
| Sowing | BYDV risk | Control action |
| Early sown (not recommended) | High | Pyrethroid at 2-3 leaf stage and pyrethroid early November |
| October sown | Medium to high | Pyrethroid early November |
| Emerging after November | Low | Control needed in mild winters, where aphids are plentiful, or in high-risk areas |
While resistance (partial) has been detected among the grain aphid population, pyrethroids (Karate, etc.) will still be effective for the majority of growers. Multiple applications of pyrethroids should be avoided to prevent the development of full resistance.