Plenty of aphids about, but March sowing has reduced risk

Aphids are a topic on many people’s minds at the minute. In the past number of years Barley Yellow Dwarf Virus (BYDV) – which is spread by aphids – has been an issue in spring barley crops and when at its worst BYDV can cause substantial yield losses.

However, April sown barley is most at risk. The good weather this spring meant that a large amount of spring barley was drilled in March and, as a result, is at a lower risk of BYDV infection.

Teagasc’s advice has been that April sown barley should be treated for BYDV at the three to five leaf stage (GS13-15). Crops can be sprayed after this timing, but are considered to be out of risk by GS31.

Past research from Tom Kennedy shows that GS14 is the ideal timing for BYDV control.

GS14 is just before tillering begins. However, crops may benefit from treatment before GS31.

March sown crops are at a very low risk of infection compared to those sown in April.

Resistance

Farmers should be aware that resistance has built up to pyrethroid insecticides and so efficacy of the product should be monitored. If poor control is achieved a non-pyrethroid spray may need to be used.

Numbers high in winter crops

Aphid counts are not carried out in spring barley crops in Teagasc and monitoring of numbers in winter crops is also complete for the season.

However, there are plenty of aphids in winter crops (which do not need to be controlled at present).

According to Louise McNamara – entomologist at Teagasc Oak Park – the abundance of aphids in winter crops poses a risk to spring crops.

Aphids on winter barley in Co. Cork last week. Image source: Louise McNamara, Teagasc

Teagasc’s advice for this season is that all spring barley crops may benefit from receiving a treatment, due to the mild winter/spring that we have just had.

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