2018 ASHS Annual Conference

High tunnels are an increasingly important technology in raspberry production. They protect the crop from rain and low temperatures, lengthening the growing season and improving fruit quality. As high tunnels have become more common, the number of materials available for covering tunnels is increasing. New plastics which block or alter natural sunlight provide growers with options. Some plastics block wavelengths in the ultraviolet and infrared ranges while others diffuse light, scattering it as it enters the tunnel. Polarized and ultraviolet light are used by many insects in navigation. Previous research showed that insect pest populations of several different orders are reduced when greenhouses are covered with UV-blocking plastics. Meanwhile, anecdotal observations indicate that Japanese beetles (Popillia japonica) are less problematic in high tunnels than in field-grown raspberries. For these reasons, we investigated the effects of various plastics on two key pests of red raspberries, Japanese beetle and Spotted Wing Drosophila (Drosophila suzukii, SWD). Research was conducted in 2016 and 2017. We grew two cultivars of primocane red raspberries, ‘Polka’ and ‘Josephine’ in high tunnels with five different plastic coverings plus an uncovered control. All plastics blocked some portion of the ultraviolet and visible range, and one also blocked infrared light. Japanese beetles were removed by hand and counted every day in 2016, and every 5 days in 2017. SWD were monitored with vinegar traps and harvested fruit were incubated to observe emergence of the flies. Foliage temperatures were measured with an infrared thermometer twice during the summer in each tunnel on the east and west sides of the rows. Fruit was harvested three times per week. Mean and cumulative beetle counts were compared for the different plastics, dates, and cultivars. Mean and cumulative trap counts and infestation rates for SWD were compared for the different plastics, dates, and cultivars. Weekly yield, and temperatures were compared between treatments and used as covariates. All plastics significantly reduced Japanese beetles. UV-blocking plastics had the lowest numbers, while the partially UV-blocking plastic which blocked some IR, was not significantly different from the non UV-blocking plastics in 2017. In contrast, SWD trap numbers were lowest in tunnels that transmitted UV-light in 2017, and highest in those that blocked it. This suggests that SWD do not need UV in order to navigate, and may favor environments without it.