Aphid numbers rise slightly; but none are winged

Aphid numbers rose slightly into the new year, but are at a much lower level than the same time last year.

A count by Teagasc on January 2 – from an unsprayed winter barley field in Oakpark, Co. Carlow – showed 12 aphids/m². This compares with 32.6 aphids/m² in the same week last year.

41% of the live aphids sampled by Teagasc on January 2 were grain aphids, while 0% of the aphids were winged. Winged aphids allow barley yellow dwarf virus (BYDV) to spread more rapidly.

Aphid numbers have kept relatively low since the end of October. In the fourth week of October 25.6 aphids/m² were counted.

As temperatures plummeted at the end of October and the beginning of November aphid numbers reflected this. The highest number of aphids reported from the same field in November was 14.7/m².

Source: Teagasc

Research from Teagasc shows that late application to previously unsprayed crops has been beneficial where aphids or BYDV is widespread.

The majority of crops would have received aphicides in the autumn. Recent cold temperatures at night should help to deter aphid activity and avoid spraying.

Growers should also remember that resistance has built up to some pyrethroid products and growers should monitor their crops for control failure. If the treatment hasn’t worked then it should not be reapplied.