Impact of Mulches on Management of Spotted Wing Drosophila, Fruit Yield and Quality

View the project final report

Commodities

• Fruits: berries (brambles)

Practices

• Animal Production: preventive practices
• Education and Training: on-farm/ranch research
• Pest Management: cultural control, integrated pest management, mulches - general, mulching - plastic, prevention
• Production Systems: agroecosystems, organic agriculture

The North Central region's fruit industry is experiencing substantial damage from the invasive spotted wing drosophila (SWD) fruit fly, with Wisconsin grape and berry growers identifying SWD as their top insect pest. Fruit growers worldwide are facing similar problems, with few effective, sustainable solutions. Management of SWD relies heavily on chemical control, which detriments economic and environmental sustainability, and does not provide adequate control of this pest. Growers apply broad-spectrum insecticides every 4-7 days, raising concerns about consequences on natural enemies, pollinators, secondary pest outbreaks, soil health, and overall land stewardship. Excessive insecticide use threatens the quality of life of farmers, as well as surrounding communities. Growers express a strong interest in alternative management strategies that significantly decrease chemical inputs and costs.

Our proposal, titled "Impact of mulches on management of spotted wing drosophila, fruit yield and quality", examined the impact of plastic mulches on spotted-wing drosophila adult and larval populations and canopy microclimate conditions relevant to the fly. We tested 3 types of plastic mulches including metallic polyethylene, black biodegradable, and white-on-black biodegradable.  We used passive trapping with clear sticky cards to assess adult populations of SWD in the canopy and the salt float method to count the number of larvae in fruit. Canopy temperature, RH, and light intensity were monitored continuously using HOBO data loggers. For a more complete view of the light conditions in the canopy, we measured radiance over 4 days using a spectrometer.

Over the two years of this study, we found that black, white, and metallic plastic mulches reduced adult SWD populations in the canopy by 41-52% and larval populations by 52-72% compared to the grower standard. The mulches did not change canopy temperature or relative humidity, but metallic mulches increased canopy light intensity compared to the black mulch. Radiance in UV spectrum (380-400 nm) was higher in the canopy above all three plastic mulches, suggesting that this could be deterring adult SWD. Future studies will determine whether changes in radiance are associated with the reported reduction in SWD  populations. In 2021, we assessed plant growth, yield, and fruit quality at our research plot established at the West Madison Agricultural Research Station, since collecting yield data and destructive sampling of fruit is not feasible on our grower-collaborator's farm. Data analysis for this objective is ongoing. Overall, plastic mulches are a promising cultural practice for managing D. suzukii since they can reduce adult and larval populations. 

We evaluated the efficacy of our research in achieving the desired outcomes by creating an advisory panel with growers (which met in 2019 and 2020), and conducting pre- and post-study grower surveys online through the Wisconsin Fruit website and at presentations given at the Wisconsin Fresh Fruit and Vegetable Conference. Our results are relevant to North Central region fruit growers experiencing damage from SWD, as well as fruit growers worldwide. Ultimately, we will provide recommendations to fruit growers for achieving more sustainable management of SWD, subsequently reducing insecticide inputs, and increasing environmental and economic sustainability of fruit production.

The expected learning outcomes for this research are as follows: 1) researchers will learn how mulch color and reflectivity affect SWD management, fruit yield and quality; 2) researchers will learn how to use mulches to effectively manage SWD and increase fruit yield and quality; 3) 30% of growers surveyed will have increased knowledge of how mulches impact SWD management, fruit yield and quality. The expected action outcomes are that: 1) growers will start using mulches for SWD management; 2) growers that use mulches will achieve more effective SWD management, higher fruit yield and quality, and decrease insecticide applications for SWD.