The follow-up inspection of seed potatoes at the NAK is going well and is well on its way. However, the results show a striking number of virus reactions and the national reduction percentage is surprisingly high.
The follow-up inspection of seed potatoes at the Dutch General Inspection Service (NAK) is going well, according to Jeroen Winkelhorst, technical coordinator at the NAK. "The follow-up inspection was able to start on time and we scaled up immediately at the start. This allowed us to keep up with the work and we are now certainly more than halfway through the follow-up inspection," Winkelhorst explains. The influx of samples for the follow-up inspection was also beneficial thanks to the good harvesting conditions and the favourable weather.
Reduction percentage higher than expected
The results of the follow-up inspection did surprise the seed potato sector with a reduction percentage of 23%. It is indeed a lot lower than last season, which came to 31%, but last season this was also reflected in the situation in the field and the vector pressure, an indicator that provides insight into the potential virus pressure in a crop. This was not the case this season. The number of aphids was not too bad compared to previous years and virus was found in the field, but clearly a lot less than in other years. This while the conditions for detecting virus in the field were also good thanks to the dark weather. The field inspection at the NAK also confirmed this: the percentage and number of plots that were reduced by virus was relatively low and few.
The NAK is also surprised by the reduction percentage, although Winkelhorst does mention a possible explanation. "If you look at the aphid situation, we had estimated it somewhat lower. It was certainly not extreme. Yet there are many setbacks and the virus is in it. I don't have one clear explanation, but later in the season there were a lot of aphids that may have caused an infection. Not everywhere, but in certain regions this can be seen in the aphid monitoring of the NAK." In addition, a lot more PBs were released this year and when a virus reaction is found, it is immediately no longer an S-class and therefore a reduction.
Winkelhorst emphasizes that the current reduction percentage is in fact an interim position, and later, when the follow-up inspection is in the final phase, it may be lower. This is partly due to the re-inspections that take place and you see them almost every year. The leaf roll virus has also been checked again since last year and this virus is also found again in the follow-up inspection. However, no figures are yet available on this.