Everything in the fight against lice and viruses

"Last season we had an 'almost super' seed potato year. The only downer was the class reduction of four plots, mainly because we did not expect that at all," says Gert Boomsma from Minnertsga (Friesland). Together with his son Jelmer, he looks back and ahead on aphid and virus control in seed potatoes. "We are really doing everything we can to prevent infections. You cannot do more than that."

It's mid-February. After a series of gray days, the sky is finally clearing up again. For Gert and Jelmer Boomsma it is no reason to open the roller doors. They are still too busy sorting. "These are Arizona's. They will soon be going to Turkey. After that we still have two batches of Fontane's ahead of us. So we will be indoors for a while in the coming days," says Gert as he stops the reading belt and offers a cup of coffee.

In the company canteen, which is built high in the ridge of the barn, father and son talk extensively about the ins and outs of their company. This year will be a special year because the farm area has almost doubled. Gert: "We were able to purchase the land from our neighbor. As a result, we have increased from over 70 to around 140 hectares. The area of ​​seed potatoes has also increased considerably to around 70 hectares. So we have a lot of extra work to do. wait, but we're looking forward to it," he laughs. 

In seed potato cultivation, the partnership mainly focuses on trunks (PB1 to PB4) and higher basic material (S and SE). The two largest varieties on the company are Fontane and Esmee. Arizona, Arsenal, Frieslander, Lugano, Palace, Paradiso, Picasso, Rudolph and Sante are also grown. To advance cultivation - and spread the work somewhat - about half of the seedlings are pre-germinated in Joppe bags. As a rule, these are Esmee, Rudolph, Picasso, Sante and some of the Fontane's. This advance paid off well last season, says Gert. "The mother tubers disappeared in time, so we were able to dig everything up on time. So we didn't have to muck around here and got everything neatly in the shed."

2023: an 'almost super' year
Although the harvest went well and the yields were also good, the partnership still had to suffer an unexpected setback. "In the follow-up inspection, four plots were lowered in class. A big setback, especially because we actually did not see this coming," says Gert. At the same time, he puts the reductions into perspective, because they are certainly not the only ones this has happened to. "For some colleagues, the follow-up turned out even worse. So let me not complain too much and call it an 'almost super' year."

The cause of the virus infections remains a matter of speculation. Son Jelmer says that they started the selection very early and that they were able to find virtually no infections in the plots in question. "It was actually a very easy selection season. That is precisely why the reductions come as a surprise." The company also says that it does not have the 'most difficult range' with regard to the variety's sensitivity to viruses. "Rudolph may be a difficult one and you also have to keep a close eye on Fontane. But varieties such as Esmee and Arizona are very less susceptible to the virus. We know that and we also anticipate that during the selection."

Closing spray schedule
In aphid and virus control, everything is aimed at an early and as consistent spraying schedule as possible. There is always consultation with Klaas de Boer from George Pars Graanhandel BV. "Although we know quite well how to approach it, it remains important to discuss matters regularly. Virus prevention and lice control are too important to miss a beat anywhere," Gert emphasizes. While he used to 'play around' with the dosages, in recent years he has been adhering more and more closely to the recommended dosage. "There is less and less confidence that things will turn out well with lower doses. The spraying must good, setbacks simply cost too much money."

Last year, virus prevention started early. The first three sprayings were carried out every three days with 3 to 4 l/ha of mineral oil. After that, a weekly schedule was maintained with a lice killer added every fourteen days. In addition to Gazelle® and Antilop® (both twice). Sivanto Prime a very important link in the fight against the virus. This systemic agent acts on three different places in the plant, providing a very good and reliable aphid kill. That certainty is worth a lot, especially when the focus is on the cultivation of high-quality seed potatoes. "Then nothing should actually go wrong in the fight against the virus," Gert emphasizes once again.

For this reason - and also because of the setbacks in the follow-up inspection - the company is considering including pyrethroids in the spraying schedule again next season. "I stopped using them because they are not pleasant products to use, both for myself and for all kinds of natural enemies in the crop. But now I have to use the mineral oil again every week. Everything that helps to combat lice has been included. ."

Straw between the mini tubers
In addition to a balanced spraying schedule, the company also tries to prevent and combat lice in other ways. For example, they have been maintaining a fairly modest nitrogen dose of 60 to 70 kg/N per hectare for several years. "As a result, the crops become slightly less green and lush, making them more unattractive to aphids. We have maintained yields well so far, partly by making additional adjustments with trace elements such as manganese, boron and zinc," Gert explains. the underlying idea.

Next season we will also experiment for the first time with a straw cover between the potato ridges. The (yellow) color of the straw should cause disorientation for the aphids, preventing them from landing on the crop. "Several colleagues have gained experience with this in the past year. Some are enthusiastic about the result, others less so. For us, this is sufficient reason to provide all mini tubers with a straw cover. The cleaner we can start, the better It is. If such a straw cover just helps a little, then it is worth it," Gert concludes.

^{Gazelle® and Antilop® are registered trademarks of Nisso Chemical Europe GmbH p/a Certis Belchim BV}

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