Potato Grower

40 POTATO GROWER | NOVEMBER 2018 New PVY control strategies in seed potatoes Different Angles SEED| By Brice Dupuis Diggin' In A book on PVY authored by a network of European researchers was published in 2017. The book presents essential research findings of recent decades and helps identify knowledge gaps. Transmited by aphids, potato virus Y (PVY) causes more problems in seed potato production than any other virus. The virus causes highly variable crop losses, depending on the infection rate in the batch and the susceptibility of the variety in question. Several control methods exist for limiting the spread of PVY, with insecticides and mineral oils being the most widespread. Alternative methods include innovative control strategies such as the use of natural defense stimulators and intercropping, as well as the combination of straw mulching and oil spraying. The most effective control measure that is commonly practiced, of course, is the cultivation of varieties that are less susceptible or resistant to this virus. Producers, however, are not always able to choose the variety they cultivate. If susceptible varieties are grown, certain cultural measures can be taken to limit the risk of infection, such as choosing healthy plants, planting far away from sources of infection, and rogueing of the diseased plants in the field. The effectiveness of these measures is limited, though, and it is essential to take direct action against the spread of the virus. In recent years, studies have been undertaken to determine the efficacy of alternative methods for controlling PVY. They include : eliCitors Numerous products are offered as natural plant defense stimulators, otherwise known as elicitors. The Swiss research station Agroscope tested the efficacy of one of these elicitors— acibenzolar-S-methyl (Bion from Syngenta)—against the spread of PVY. The product was field-trialed for two years and demonstrated an average efficacy of 10 percent, as opposed to the 14 percent efficacy of the insecticide tested in the same trial (λ-Cyhalothrin, Karate from Syngenta). However, there are other elicitors on the market with modes of action that differ from that of acibenzolar-S- methyl and which it would be worthwhile testing against PVY. CroP borders & ground CoVer In North America, crop borders are frequently used to control the spread of PVY. This approach involves surrounding the main crop with a wide border of a plant or mixture of plants that are not susceptible to PVY, thereby creating a natural barrier to penetration by the aphids that transmit the virus. The non-host border plants cause aphids to shed their virus load after several test bores into them. The efficacy of crop borders is highly variable, ranging between 20 and 60 percent in trials. Theoretically, the way in which crop borders work (i.e., as aphid barriers and virus traps) ought also to apply for intercropping, which is why Agroscope decided to test intercropping with oats and with hairy vetch as new methods for controlling PVY. Results over the two years of the trial were promising, with an average efficacy of 33 and 34 percent for the vetch and oats, respectively. However,

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