Does Warm Weather Bring An Early Lice Invasion?

Last growing season had a very high aphid pressure. As a direct result, 25% of all seed potatoes were reduced in class during the follow-up inspection by the NAK inspection service. It is a result of the Y virus. The NAK therefore expects to find many infected tubers next season.

The warm winters make it easier for the aphids to overwinter. The aphid pressure is already relatively high early in the season; The NAK cannot say how high exactly. As a rule, they only start monitoring the lice population via suction traps on May 1. This is followed by 'knocking' and catch bins are placed later in the season. This year, the NAK will start catching 'soon', it says.

British warning
The British research institute AHDB does this all year round research to the lice population. The grain aphid and green peach aphid in particular are monitored using suction traps spread throughout the country. The AHDB warns that lice pressure could occur an average of 2 weeks earlier this spring. The direct reason for this is the unusually high temperature in February.

Supplier Crop Solutions, whose partners include CZAV, CAV Agrotheek and Heyboer, started installing sticky traps in mid-March. This happens at a number of locations, mainly spread across the southwest, the Noordoostpolder, the Wieringermeer and the province of Drenthe. Cultivation advisor Arjan de Vries is involved in the aphid count on behalf of CAV Agrotheek: "Last autumn we continued to monitor aphids until well into November. We kept catching them in lilies and grain."

Real danger
De Vries does not yet have any figures for the Netherlands, but the warning from British colleagues does not sound strange to De Vries. "The first aphids can be found in sheltered places, often in gardens on rose bushes. The temperature there can quickly rise to 20 degrees Celsius, so the population multiplies very quickly. You encounter them much later in the field."

Crop Solutions has been monitoring lice pressure for about 8 years. The aim is to use crop protection products more effectively and at the right time. Bayer supports Crop Solutions and publishes data on their website every week. "Bayer attempted to create a prediction model based on the temperature sum and capture data. This was disappointing because the connections are difficult to make," says De Vries. This finding is somewhat at odds with the British study, which says there is a direct link between temperature and lice population. AHDB bases their warning system on this, linked to suction traps.

Effect of night frost
The sunny days at the end of March also bring night frost, which slows down the lice population. De Vries thinks that this has a braking effect, but does not eliminate the problem. "A low temperature is positive, but the initial population is higher. We know from experience that aphids can overwinter well in grassland. Aphids are also found in wheat and have sometimes already been sprayed to prevent the barley yellowing virus."

On behalf of CZAV, consultant Hanko Blok in Zeeland is responsible for lice monitoring. This is already starting now, because it is current in the cultivation of tulips. However, these findings are also used for other crops. "Last year we saw higher peaks in the autumn than in the summer," he says. "We have the feeling that flights will take place on time, partly due to the mild winter."

Vector value
Profytodsd and Pars Granenhandel organized a virus symposium at the end of February, together with HZPC and Agrico. The lice population was also mentioned there and the fact that it can become active surprisingly early to transmit the Y virus. The type of louse is also important. One type transmits the virus 1-on-1, while the other does so less effectively. That is why we talk about the vector (value).

The NAK inspection service therefore identifies all lice. However, Crop Solutions' research does not do this. The lice species that are now being warned about have a very high vector value and transmit the virus directly.