Rain will push spring barley to final fungicide timing

The rain in the past number of days was welcomed by spring barley crops which had been beginning to struggle in the dry conditions.

Crops may see a burst of growth in the coming days. As a result and depending on growth stages sprayers will be making the trek to the field once again.

For the most part, the dry conditions have helped to keep disease to a minimum.

Crops in general are clean, but rhynchosporium is present in crops which have not yet received a fungicide. There is also mildew present in some of the varieties prone to the disease, particularly those which have not been treated.

Final fungicide

The coming days and weeks will see crops reach final fungicide timing. Teagasc results show that the highest return on yield comes when the T2 is applied to spring barley from between the time the flag leaf has emerged and when the awns are visible.

Chlorothalonil should be applied in all final spray programmes on barley to prevent ramularia and as part of an anti-resistance strategy to protect other chemistry. It should be applied at a rate of 1.0L/ha.

Leaf wetness plays a role in the severity of ramularia on barley and as the days of leaf wetness increase so to does the the risk of ramularia.

An SDHI and a triazole should also be applied to fight the main diseases – rhynchosporium and net blotch.

When deciding on application rates growers should take into account disease pressure as well as anti-resistance strategies.

Where mildew is present it may be advisable to apply a mildewcide to the crop. However, growers should take note of the level of infection and the disease resistance score of the variety before applying a mildewcide. A high rating may mean that the SDHI/triazole mix will suffice.

Some disease resistance ratings from the 2019 spring barley recommended list. Data source: DAFM

Applying a strong final spray will ensure a longer green leaf period and help to strengthen the plant, which may help to reduce straw breakdown.

Where growers think disease pressure is low they may decide to apply chlorothalonil with a triazole or chlorothalonil with an SDHI, but not as part of a mix. Once again it is important to know your varieties.