Aphid numbers have dropped back from their high at the end of October. Numbers at Teagasc Oakpark reached 25.6 aphids/m² in the fourth week of October, but cold weather last week more than likely contributed to a dramatic drop in numbers to 4.9 aphids/m².
Of the aphids sampled at the end of October, 32% of the live aphids were grain aphids and 17% were winged.
Winged aphids can spread Barley Yellow Dwarf Virus (BYDV) quickly.
Data source: Teagasc
This time last year
In the first week of November last year, 16.3 aphids/m² were counted from an unsprayed crop of winter barley from Oak Park.
Samples taken from unsprayed winter barley
It should be noted that these figures are only an indication of numbers from one unsprayed area of winter barley and will vary countrywide.
Action
Heavy rain this week will not make spraying an attractive option and farmers should not make their way to the tramlines unless absolutely necessary.
If cold temperatures prevail at night time, the risk of aphids will decrease. Barley that has not received a seed treatment or a pyrethroid is most at risk.
However, if a crop has not already received a treatment then it was most likely late-sown and may be okay without a pyrethroid application if temperatures drop.