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diggin’ in PEST MANAGEMENT “Currently available insecticides cannot prevent transmission of PVY since the aphid vectors require only a few seconds of probing for the acquisition and transmission of the virus. However, they can reduce the spread of PVY by pre- venting aphid colonization on the plants.” the two viruses cause yield and quality reduction in the tubers, managing PVY and PLRV is a priority for both seed and commercial growers. NON-PERSISTENT TRANSMISSION (PVY) Viruses transmitted in this way are located on the surface layer of plant leaves. Acquisition time: non-persistently transmitted viruses are acquired rapidly from plants, usually in minutes or seconds. Since the virus is located on the surface layer of infected plant leaves, the mouthparts of the aphid get contaminated with virus particles in the brief process of probing (sampling of the sap in the epidermal cells in order to find a suitable host). The probing behavior is ideally suited to rapid acquisition of non-persistent viruses. This is why cereal aphids can spread PVY. Inoculation time: Once the virus is acquired by the aphid mouthparts, aphids transmit these viruses in a few seconds while feeding on other plants, since there is no latent period. The virus remains on the aphid for a short time (< 2 hours). Longer retention times have been reported for non-feeding aphids, which could explain long distance transport of PVY by aphids. The age of the plants is known to have an effect on virus transmission, with acquisition from and inoculation to young plants usually presenting higher transmission rates. Also, it has been demonstrated in Idaho that some PVY necrotic strains are better transmitted than other strains. Two potato-colonizing aphids, the green peach aphid and the potato aphid, are the most efficient vectors of PVY. Although the bird cherry oat aphid, a cereal aphid, is not an efficient PVY vector, it is still considered a very important vector because of its high numbers, which usually start increasing by the first week of July and reach maximum levels near the end of the month, coinciding with the maturing of cereal crops. Winged bird cherry oat aphid forms are obviously more important in transporting the virus into and within fields when they migrate long distances to find suitable plant hosts. The molecular details of the aphid- virus interactions are becoming better understood and recent studies have demonstrated that most processes are www.potatogrower.com 21