A bacteria-like pest of apple trees across Europe has appeared for the first time in North America in an orchard now under federal quarantine in Nova Scotia.
Apple proliferation phytoplasma (APP), a yield-reducing quarantine pest in both Canada and the U.S., has been confirmed in Pacific Gala apple trees in the orchard near Kentville after being detected last year.
The affected trees were imported from the U.S. in 2008, but the Canadian Food Inspection Agency emphasized in a release Friday that “at this time the actual source of infestation is unknown.”
CFIA said it has notified the U.S. Department of Agriculture (USDA), which is now testing at the source nurseries.
However, USDA has said, no symptoms of APP have been observed in the source nurseries or reported in the U.S. at large. CFIA hasn’t yet imposed any restrictions on importation of apple trees from the U.S., USDA noted.
“At this time it is unknown if APP is present in any other areas of Canada or the U.S., or if this was an isolated incident,” CFIA said in a release.
That said, the agency is now consulting national stakeholder groups and the provinces on “potential regulatory actions” and will announce more information on those decisions at a later date.
Symptoms of APP include a “broom-like” appearance of branches, development of abnormal leaf clusters (leaf rosetting), reduced fruit size, weight and sweetness, and decreased overall tree growth and viability.
The pest has no effects on human or animal health, but given its effects on the fruit, APP is considered one of the most economically important apple diseases in Europe, causing economic losses of 10 to 80 per cent, CFIA said. There are no known treatments for the pest, the agency added.
The pest spreads through propagation practices, such as tree budding or grafting with infected material, so long-distance dispersal follows through the trade and use of infected rootstock, scionwood or budwood — and by way of specific insects. APP isn’t transmitted through seed, fruit or pruning, CFIA said.
Some branches on an infected tree may appear normal and produce normal fruit, while other branches show symptoms. Furthermore, symptoms can disappear for one or more years, then reappear after heavy pruning or grafting.
A type of froghopper and leafhopper known to be insect vectors for APP have been reported in British Columbia and Ontario, but their efficiency to spread APP in Canada is “unclear” and there are no other known potential insect vectors for the pest in Canada, CFIA said.
APP has previously been detected in Albania, Austria, the Balkans, Belgium, Bosnia-Herzegovina, Bulgaria, Croatia, Cyprus, the Czech Republic, Denmark, France, Germany, Greece, Hungary, Italy, Moldova, the Netherlands, Norway, Poland, Romania, Russia, Serbia, Slovakia, Slovenia, Spain, Switzerland, Syria, Turkey and Ukraine.
The pest has been reported in Europe in other species such as oaks, hazelnuts, hawthorns, plums, magnolias, dahlias, roses and European and Asian pears, but APP’s impact on those “secondary” hosts remains unclear, CFIA said.