Aphid numbers dropped in the last week of April. An average of just 4.1 aphids/m² were counted on April 25. The aphid counts were carried out in an unsprayed winter barley crop in Teagasc Oak Park, Co. Carlow.
This is the last aphid count that Teagasc will supply this season.
Of the average 4.1 aphids/m², 17% of these aphids were grain aphids. 0% of these aphids were winged. Winged aphids carry barley yellow dwarf virus (BYDV) and cause it to spread. Aphids which are not winged can also carry the virus, but not to the same level or speed.
Rainfall and temperature
The average air temperature in Teagasc Oak Park was 9.0°C in April 2018 and 2017, according to Met Éireann.
Rainfall levels were significantly higher in April 2018 – 73mm – than in April 2017 – 15.8mm.
The table below shows the weekly aphid counts (aphids/m²) for the 2016-2017 season and the 2017-2018 season.
Data source: Teagasc
Advice
The advice from Teagasc remains the same. An aphicide should be sprayed at GS14. Late-sown spring barley crops are at high risk, especially when temperatures begin to increase.
It was also noted by Teagasc that these aphid counts are taken from one winter barley field in Co. Carlow and that conditions may vary across the country.