Aphid numbers 15 times lower than the same time last year

Aphids certainly aren’t a problem for crops at the minute. But it is interesting to compare aphid counts with the same time last year in a different weather scenario.

In the first week of April 2017, the aphid count – carried out by Teagasc – measured 156.4 aphids/m². In 2018, that figure was just 10.2 aphids/m². 47% of the live aphids were grain aphids and 0% of these aphids were winged.

Numbers have been relatively low since last October; but aphid numbers did hit 70/m² at one point in December of the 2017/2018 season. This was the highest count recorded since October 2017.

In the 2016/2017 season, aphid numbers decreased significantly from November to February. However, they increased again in March as temperatures rose. In March of this year, aphid numbers remained below 22 aphids/m². While numbers hit more than 70 aphids/m² at the end of March last season.

The weekly average aphid count for the months of October to April are detailed in the table below.

Weather impact

The air temperatures (°C for Teagasc Oak Park) for the months of October to April are detailed in the table below.

Data source: Met Éireann

Aphid numbers decreased with temperature. In the winter of the 2016/2017 season, aphid numbers dipped with the drop in temperatures. However, aphid numbers have remained low this winter with the low temperatures.

Heavy rainfall and snow can result in a decrease in aphid numbers. These difficult conditions can also make it hard to carry out aphid sampling.

Aphicide

April-sown barley is always classified as being at a high risk of barley yellow dwarf (BYDV) infection (spread by aphids). As temperatures are set to rise, and the majority of spring barley crops are yet to be planted, an aphicide will still need to be applied – preferably at GS14.