MADISON, Wis. (AP) - Wisconsin researchers are trying to learn more about an invasive fruit fly that has been threatening berry crops in the state since 2010.

University of Wisconsin fruit crop entomologist Christelle Guédot tells Wisconsin Public Radio that researchers started trying to pinpoint when and where the spotted wing drosophila is most active within plants last summer.

She says the research could help growers get a better idea of when to spray insecticides. They're also examining if temperature and humidity play a role in the insects' distribution.

Eric Carlson owns Blue Vista Farm in Bayfield. He says he has to spray his crops every week to control the pests, which has increased his production costs.

Results of the study should be available by the end of the year.