Sustainable Pest Management Approaches for Raspberry Growers

View the project final report

Commodities

• Fruits: berries (brambles)

Practices

• Crop Production: high tunnels or hoop houses

Since the invasive fly, spotted wing Drosophila (SWD) (Drosophila suzukii) was detected in the U.S., it has created serious problems in sustainable berry production. Few alternative controls beyond chemical control exist for control of this pest, and new management techniques are needed. Growing berries under protected culture is a new and growing method for season extension, but may also be a way to control this invasive fly and other pests. This project explored sustainable pest management in high tunnel raspberry production through the use of ultraviolet-reducing plastics and exclusion netting. We investigated the ability of plastics to prolong pesticide residual activity and to mitigate pest damage, especially in conjunction with SWD. We also investigated the utility of exclusion netting to control SWD and other pests in high tunnel raspberry production. Reducing ultraviolet light did not impact pest populations, including SWD, but did extend the residues of some chemicals on the leaves of raspberries. We also found that exclusion netting resulted in an average reduction of 73% and 4-week delay in the arrival of SWD in high tunnels. Implications of these results are discussed below. This aids in the development of sustainable and cost-effective production methods for berry growers and helps ensure supply of these nutritious fruits into the marketplace.

Introduction:

The demand for fresh, sustainable, and local food is increasing with berries becoming especially popular. As a result, the number of berry growers in the U.S. increased by 20% in 2012 compared to 2008 (USDA-NASS 2014). However, growers, particularly in northern regions, face many challenges in their production. While almost half of the berry farms in the U.S. are located in the North Central and Northeast, over 80% of raspberry production comes from the Pacific Northwest (USDA-NASS 2014).  One of the key limiting factors for these northern growers is the climate, including excessive rain, short growing seasons, and harsh winters (Hanson et al. 2013). 

Raspberry growers face many insect pests including Japanese beetles, cane borers, raspberry sawflies, aphids, and spider mites (Funt 2013). Additionally, growers face a new threat from the invasive fruit fly, spotted wing Drosophila (SWD) (Drosophila suzukii). SWD was first detected in the western U.S. in 2008, and was later detected in the Midwest in 2010 (Lee et al. 2011; Isaacs et al. 2011; Asplen et al. 2015). The crops of concern are soft-skinned fruit including raspberries, blueberries, and strawberries, with raspberries being the most susceptible crop (Burrack et al. 2013, Bellamy et al. 2013). In 2014, SWD caused estimated economic losses of $159 million in U.S. raspberry production (Burrack et al., unpublished data). Currently, the main control method is limited to pesticide applications. Because SWD has rapid population growth, growers often spray insecticides weekly during harvest, abandoning their sustainable integrated pest management programs (Lee et al. 2011). There is an urgent need to develop sustainable management practices to decrease insecticide dependence in this system.

High tunnels are a promising solution to both the climatic and pest management hurdles that these growers face (Gaskell 2011, Hanson et al. 2011). These large and unheated protective structures are covered in plastic during the growing season, allowing for earlier harvest in the spring and later harvest in the fall (Demchak 2009). This extended growing season allows raspberry production to become more lucrative, selling before or after the peak in production. Berries grown in high tunnels also tend to have increased shelf-life and decreased disease and pest incidence, making the fruit eligible for sale at farmers markets or grocery stores for premium prices (Demchak 2009, Hanson et al. 2011). However, the advantages of high tunnels need to be better explored, especially given the high initial investment which can deter growers (Conner et al. 2010). High tunnels allow for the possibility of light manipulation through the use of specialty plastics covering the structures, and for physical management options, like exclusion netting, to control insect pests.

The objectives were to determine if protective structures can allow for innovative and sustainable pest management practices, including the use of specialty plastics and physical exclusion. More specifically, our objectives were to:   

1. Determine the effect of ultraviolet light penetration under protected culture on pests, natural enemies, and pollinators
2. Determine the effect of varying levels of ultraviolet light penetration on pesticide degradation over time
3. Determine the effect of exclusion netting on high tunnel raspberry for controlling SWD and other insects