The seed potato industry in Southwest Netherlands takes an increasingly important place in the arable area. Reason for CZAV to organize a cooperative seed potatoes study group 'the integrated approach of the seed potatoes' cultivation in that region. Three CZAV-advisors let their light shine about viruses in seedlings, fertilization strategies and virus tests at ground Zwaagdijk.
Initially in the first round the growers got a presentation about the biology and control of bacteria diseases in seed potatoes lectured by Jan der Wolf, employee bio-interaction and plant health at WUR in Wageningen.
One of the striking conclusions from the virus tests at testing ground Zwaagdijk is that peppermint oil seemed very promosing as new virus fighter in seed potatoes. Karel Steijaert (EMT at CZAV): "There are less and less applications that are allowed, labels change and intervals have to be adjusted. It's needed that alternatives are being introduced. The amount of lice killers are restricted. The virus tests also showed that mineral oils being maintained - also in periods of drought in seed potatoes - continues to be essential for the prevention of viruses in seed potatoes. Peppermintoil as additive on existing virus control has been proven as added value for seed potatoe growers."
Growers are searching a nature friendly product with excellent effect. According to Stijaert there seems to be a breakthrough: "Our idea is that peppermintoil fills the gap that many chemical products leave behind due to restrictions by law. At the CZAV work environment, we have seed potatoe growers that used peppermint oil the past growing year. They have good experiences piece by piece with this innovative product. It will depend on the development of results the coming years, but the past 3 years there seems to be promising virus reducing results. If this line continues, growers will switch very fast, because the products they use at the moment will become more limited, think about Actara that became illegal this year. We think that the moment to expand widely with this product is very near.
Also the fertilizing tests show new trends: leaf fertilizers are becoming more popular. CZAV-advisor Lennar Testers: "The goal of fertilizing is to get an accelerated starter development, to havest more tubers and to create a resilient crop. That can be done by means of granules in row, add calcium or delayed fertilizers such as Exacote in a positive tuber development. Crucial is to only give what is needed, because only then fertilization will also have effect for a significatn yield increase. Leaf fertilizers are also more interesting by the stricter legislation, because more and more growers have to go look for trace elements during cultivation.
Lein de Visser took the visitors to the study evening before the break with the vision of CZAV on viruses in general and the emphasis laid on high virus pressure. De Visser: "A good virus control in seed potatoes is a total picture of soil health and plant health. Viruses are a major problem and ensure a reduction in the post-control by NAK. Growers are used to crop protection and fertilizers to see independently of each other, but as seed potato growers we need to work towards an integrated approach. Because the total picture has to be right to obtain high-quality seed potatoes to deliver. The toolbox of plant protection products is getting lower and therefore a healthy soil is even more important."
Chicory and chicory virus carriers Y virus
De Visser continues: "A healthy soil starts with digging a profile pit and good drainage. In addition, the building plan and the rotation (for fruit) has to be right: how many grains (rest crops) are there in that building plan? And brings the current cultivation rotation virus carriers? As it is well known that crops such as Chicory or Endive virus are carriers of the Y-virus in seed potatoes, plants in the neighbouring crop or storage crop."