Researchers in Manitoba are testing aphids for viruses harmful to potatoes. Results will be released later this fall.
Potato viruses can be a serious problem because certifiers will reject seed lots if there is a low incidence of potato leaf roll virus and potato virus Y.
Leaf tests from Manitoba seed potato fields in 1988 by Manitoba Agriculture and the Agriculture Canada research centre in Brandon, Man., found low virus levels. However, later testing of tubers found higher levels in some fields.
In 1999, the project expanded to include commercial and seed potato fields.
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Researchers are trying to determine prevalence of potato viruses in order to evaluate the spread, to monitor aphid movement and to detect the presence of aphids carrying viruses.
Both the green peach aphid and potato aphid are capable of transmitting potato leaf roll virus and potato virus Y.
The green peach aphid is the more efficient vector of potato leaf roll virus and is found in abundance in the Red River Valley.
Researchers set up insect traps across southern Manitoba, including fields at Shilo, Portage la Prairie, Winkler, Holland, Carberry and Carman.
They also inspected these sites and another at Minto for disease symptoms. They will collect tubers this fall from all fields and assess them for viral infection.
Both green peach aphids and potato aphids were detected at most sites. Captured aphids will be tested at the federal Potato Research Centre in Fredericton, N.B., to determine if they carry the viruses.
The University of Minnesota’s Aphid Alert program has found that, as of the third week in September, captured winged green peach aphids tested negative for potato leaf roll virus and potato virus Y.
Origin important
Researchers think the first aphid migrants arriving in a potato field may not carry potato viruses because they originate from other host plants. Aphids occurring within a potato field are more likely to acquire and transmit potato viruses.
Manitoba researchers assumed there would be larger amounts of viruses present in potato seed lots this year, and visual assessments have confirmed their theory.
A comprehensive post-harvest test this fall in Fredericton will assess virus levels in tubers collected from field sites.
For more information, contact Debbie McLaren, crop production pathologist, at the Brandon Research Centre 204-726-7650 or e-mail at dmclaren@em.agr.ca.
