The outbreak of outbreaks of phytophthora in parts of the country and an unprecedented high virus pressure are putting the situation in potato crops on edge. The dreaded potato disease has been reported in the provinces of Drenthe, Overijssel, Flevoland and Limburg, among others.
Consultancy firm Delphy made Friday 14 June notification of the discovery of phytophthora in various places in Drenthe and Overijssel. The Limburg Agrea is now also giving a waarschuwing off. Due to a combination of moisture and high temperatures, the conditions for the spread of the disease are now ideal.
Bio-plots affected
Potato plots with phytophthora have also been found in Flevoland. This has been confirmed by Chris Boone, Heyboer's branch manager in Biddinghuizen: "We find infected leaves in various places in Flevoland. However, the infection is not that bad. Especially in seed potato plots something is found, because the growers here are selecting and the crop so take a close look."
According to Boone, potato growers are on top of the situation. That means not running out in the spraying schedule. "The potatoes are growing dense. If you get phytophthora at the bottom of the crop, and a new leaf growth on top, it can remain dormant in your crop throughout the season. You can prevent this by acting now. We also find some damage in some organic varieties, with especially in the non-resistant older varieties. However, with the current combination of moisture and heat you can probably find an affected leaf everywhere in the Netherlands."
Another concern for potato growers is the very high aphid pressure. Inspection service NAK started monitoring the aphid pressure in week 24, for which traps have been installed throughout the Netherlands. At the moment there are already a lot of virus-transmitting lice present, so says it.
Extremely high lice pressure
An accumulated vector pressure of 110 was found in Witteveen in Drenthe, compared to 50 last year. "The situation in other parts of the Netherlands is similar," the NAK reports. Some consultancy companies (such as Profytodsd) also monitor the vector pressure of aphids themselves. They have been doing that since the end of May. Pressure is also high in the catch tanks of this company, with the location in Biddinghuizen being the highlight. The vector pressure there reached 90 at the end of last week.
Heyboer, who is located there and also monitors the pressure, agrees. "Everyone is alert to the high aphid pressure. Consumer potato growers are already spraying against aphids and Colorado potato beetles to keep the pressure low."