A female spotted wing drosophila lays eggs on a cherry.
PHOTO BY PETER SHEARER, OSU
Fluctuating populations of spotted wing drosophila from year to year are keeping growers in the Pacific Northwest guessing. After relatively little pressure in 2011, the fly came back with a vengeance in 2012.
Growers in Europe are also seeing fluctuations. European Fruit Magazine reports that after serious infestations in 2011, various European countries suffered less damage in 2012.
“In 2011, entire crops were destroyed in various places by the actions of this insect,” the magazine reported in its January issue. “Therefore, the fear was that in 2012 the damage would be more extensive.”
Dr. Roland Zelger, researcher with the Laimburg Research Center in South Tyrol, Italy, reported that only small numbers of spotted wing drosophila were trapped during the 2012 growing season, but large numbers were caught in October.
Zelger believes spotted wing drosophila will not cause serious damage to orchards every year, but perhaps once every four or five years, though the reason for this is unclear.