Idaho Sees Few New Spotted Wing Drosophila Finds

Dread pest may not be a major threat to state's crops.

Published on: Sep 19, 2013

By T.J. Burnham

Fortunate for the producers in Idaho, the spotted wing drosophila fruit flies don't seem to be gathering for an all-out crop attack this year.

The exotic fly which threatens an array of fruits isn't mounting a population threat, according to University of Idaho pest-watchers. Since adults were found in a Fruitland orchard in early summer, monitoring efforts continue in the south state.  Only small numbers of adult flies have been trapped, says Jim Barbour, a Parma-based integrated pest management specialist, and superintendent of the  UI Parma Research and Extension Center.

"Fortunately, the numbers are low," he says. "perhaps due  to hot, dry conditions which are not suitable for rapid population growth of  spotted wing  drosophila."

Spotted wing drosophila
Spotted wing drosophila

The pest was first found in Idaho a year ago and concerns have run high as to rather it would overwinter and return this season. Since the original find in Latah County, UI Extension has monitored the pest in southern and parts of northern Idaho.

A two-pronged approach to monitoring is led by Barbour and Stephen Cook, a UI associate professor of natural resource entomology in Moscow, Idaho.

Barbour monitors commercial orchards in western Treasure Valley between Marsing and Fruitland, and Cook is responsible for the area of wild land fruits near Clearwater.

"It's potentially a very serious threat," says Barbour. "We don't know what the impact is going to be yet because we don't know what their dynamics are going to be in this area. That's one of the reasons we're trapping and monitoring."

Presence of the fly in the June find earlier this year is considered to be good evidence that the insects may overwinter in Idaho.

Unlike the fruit flies that already occur in the state, the spotted wing has a stronger ovipositor, which allows them to puncture ripening fruit with tougher skin. Other fruit flies can only lay eggs in overripe or damaged fruit.