by Deborah Jeanne Sergeant
First introduced in 2011, spotted wing drosophila has been affecting cherry harvests. Cornell researchers studied the impact on tart and sweet cherry crops in New York State and estimated a 2% loss. That estimate jumped by 78% for both tart and sweet cherries in the year to follow, resulting in a $3.5 million loss. Juliet Carroll, plant pathology and plant microbe biologist with Cornell’s Integrated Pest Management program, said that the pests may total an 80% loss for 2019. Carroll spoke about SWD in a recent webinar hosted by Cornell.
SWD infest cherries with their eggs, which emerge from inside the fruit as larvae that pupate partway outside the fruit.
“It’s not very appetizing at all,” Carroll said. “The little larvae are one to three millimeters long, so they’re very hard to detect. Invasive species are very disruptive to IPM.”
She described the Lake Ontario region’s cherry crop as “devastated” by SWD. Carroll thinks that IPM can represent an approach to protect the crop. It begins with monitoring for SWD.
“IPM monitoring informs the grower when they need to spray so they can tailor their spray program and reduce unnecessary sprays,” Carroll said.
The monitoring results in 2018 showed that few to no SWD sprays were needed on inland orchards, which “underlines the importance of IPM monitoring,” Carroll said.
The earliest trap catch was within a mile’s radius of Lake Ontario. Near the lake, the first catch was three to eight weeks ahead of the harvest. By using trapping, the IPM program could tell when SWD was beginning to populate the area and thus protect the crop from infestation. Growers could strategically plan their spraying instead of arbitrarily spraying for the pest.
IPM is not the same as organic management. While organic management eschews manmade chemicals to treat crops, IPM assists farmers in working toward using chemicals as the last resort, and then only with as little as will be effective.
Carroll said the Lake Ontario region is a microclimate where SWD arrives earlier and builds up sooner than in other areas. The area also has a later cherry harvest, typically. “This combination places cherries at extreme risk of spotted wing infestation,” Carroll said. “Spotted wing IPM informs the timing of sprays and New York cherry growers protect their fruit.”
She added that Cornell’s IPM program is working to help cherry growers statewide to learn more about SWD, as well as explore an easier trapping method so growers can use it on their own farms. These efforts should help farmers use fewer insecticides, save money and protect the environment and human health. “They may even plant more cherry orchards,” Carroll said.
She encouraged anyone interested in learning more about SWD to visit nysipm.cornell.edu/agricultural-imp/fruits/pest-alerts-fruits/spotted-wing-drosphilia and fruit-cornell.edu/spottedwing and blogs.cornell.edu/swd1.