Seed potato growers seem to have completely lost their grip on the virus. Declassification percentages of more than 30 percent have been the rule rather than the exception in recent years. Technical advisor Fokke Smit of Certis and crop protection specialist Jan-Willem Scherpenisse of Van Iperen argue for a comprehensive plan of attack to turn the tide. "Clean seed and start on time with Oil-H are a must," said Scherpenisse.
The figures from the NAK inspection service speak volumes: more than a third of the seed potato volume has been reduced in class in recent years due to virus infections, making it a bigger problem than bacterial disease. "Seed potato growers are aware of this," says Fokke Smit. "In conversations they say that they are doing everything they can, but nevertheless cannot get rid of the virus problem. After further questioning, it often turns out that their approach can be improved in certain areas. Prevention deserves even more emphasis. Even approved starting material is not always free of Y- virus. A clean plot and clean seed are the first requirements in the fight against virus, followed by cultivation measures."
Clean plot, economical with nitrogen
Start cultivation free of potato storage and weeds. Weeds can also be host plants. Clear this up well before planting, otherwise the aphids will have an attractive landing site in the first spring flight. With the basic fertilization, be moderate with nitrogen. Excess gives a strong growth impulse and relatively many young, green leaves, which aphids find very attractive. Another measure that can reduce the aphid pressure is sowing a barrier crop next to the seed potato plot. Wheat is very suitable for this, because it remains green for a long time and attractive to lice. Last but not least experts point out the possibility of alternating virus-sensitive seed potato varieties with virus-resistant varieties.
Start early with Olie-H
A frequently asked question is when exactly should spraying be started. "My message is: start on time with Oil-H, when 20 to 25 percent of the plants have emerged. Certainly not later. Why? Because there are already attractive plants on the back before the first flying aphids, which they can infect with virus. If you don't tackle them, you already have the first sources of infection in your crop. Also, make no mistake about the growth rate. If it is 20 to 25 percent above, it can be more than 50 percent within a few days," says Jan-Willem Scherpenisse. "Sound prevention requires a short interval of 3 days between the first and second sprays with Oil-H ", adds Smit. "Last year there were already aphids present before the emergence of the potatoes. The early warnings in sugar beets are clear evidence of this. In addition, modern field sprayers lend themselves to precise spraying. This is especially efficient during the emergence period. Good experience has already been gained with this in practice."
Preventing lice population
"In addition to Oil-H, for the prevention of virus transmission, you will regularly use an insecticide such as Gazelle should be used to suppress population growth," says Smit. "When you switch to another drug, choose one from a different chemical group. A measure that no seed potato grower should forget is consistent selection. Start on time and remove all sources of infection as accurately as possible. If you follow this system approach closely, you should be able to keep your seed potato cultivation virtually virus-free."