Plastic mulches reduce adult and larval populations ofDrosophila suzukiiin fall-bearing raspberry

Abstract

The invasive spotted-wing drosophila, Drosophila suzukii, is a major pest of fruit crops world-wide. Management of D. suzukii relies heavily on chemical control in both organic and conventional systems, and there is a need to develop more sustainable management practices. We evaluated the efficacy of three colors of plastic mulches at reducing populations of D. suzukii in fall-bearing raspberry and assessed the mulches' impacts on canopy microclimate factors relevant to D. suzukii. Black, white, and metallic plastic mulches reduced adult D. suzukii populations by 42-51% 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 the visible spectrum (401-680 nm) was higher for the white and metallic mulch plots, but the black mulch plots did not differ from the control. In the UV spectrum (380-400 nm), all three plastic mulches had higher radiance than the control plots. Future studies will determine whether changes in radiance are associated with the observed reduction in D. suzukii populations. Plastic mulches are a promising cultural practice for managing D. suzukii since they can reduce adult and larval populations and could be incorporated into an integrated pest management program in both organic and conventional systems.

Plastic mulches reduce abundance of some arthropods but are not detrimental to pollinators in primocane raspberries

“…Covering the ground with UV-reflective material may disrupt orientation and flight (Shimoda & Honda, 2013). Radiance measurements taken concurrently with this study in the same research plots found that the mulches increased canopy radiance in the UV spectrum (McIntosh et al, 2021(McIntosh et al, , 2023. This may explain why the metallic mulch decreased the abundance of Coleoptera, micro-Hymenoptera, Opiliones, Orthoptera, and Thysanoptera, why the white mulch decreased Opiliones and Orthoptera, and the black decreased Orthoptera and Thysanoptera in all weeks of the study compared to the control (Croxton & Stansly, 2014;Frank & Liburd, 2005;McIntosh et al, 2021McIntosh et al, , 2023Nottingham & Beers, 2020;Nottingham & Kuhar, 2016;Rhainds et al, 2001;Summers et al, 2010).…”

“…Different colours of plastic mulches can reduce specific pests in fruit and vegetable crops, including aphids (Ban et al, 2009;Farias-Larios & Orozco-Santos, 1997;Greer & Dole, 2003), whiteflies (Simmons et al, 2010), Asian citrus psyllid (Croxton & Stansly, 2014), tarnished plant bug (Lygus lineolaris (Palisot de Beauvois); Rhainds et al, 2001), Mexican bean beetle (Epilachna varivestis Mulsant; Nottingham & Kuhar, 2016), and pear psylla (Cacopsylla pyri (L.); Nottingham & Beers, 2020). Recently, we showed that plastic mulches can effectively control spotted-wing drosophila (Drosophila suzukii Matsumura) in raspberries (McIntosh et al, 2021(McIntosh et al, , 2023. Few studies have directly tested the mechanisms by which the plastic mulches control insect pests, though it is likely related to microclimate modifications like increased reflection of light into the plant canopy or unfavourable changes in canopy humidity or temperature (McIntosh et al, 2021(McIntosh et al, , 2023Nottingham & Beers, 2020;Nottingham & Kuhar, 2016).…”

“…Recently, we showed that plastic mulches can effectively control spotted-wing drosophila (Drosophila suzukii Matsumura) in raspberries (McIntosh et al, 2021(McIntosh et al, , 2023. Few studies have directly tested the mechanisms by which the plastic mulches control insect pests, though it is likely related to microclimate modifications like increased reflection of light into the plant canopy or unfavourable changes in canopy humidity or temperature (McIntosh et al, 2021(McIntosh et al, , 2023Nottingham & Beers, 2020;Nottingham & Kuhar, 2016). These microclimate modifications may affect non-target arthropods present in the plant canopy.…”

“…These microclimate modifications may affect non-target arthropods present in the plant canopy. Further, the continuous cover and hot surface temperatures of plastic mulches (McIntosh et al, 2023;Tarara, 2000) could also impact ground-dwelling arthropods. Thus, plastic mulches likely do not exclusively target pest insects and could negatively impact other arthropod communities, with wide-ranging implications like disrupting natural pest control and pollination services.…”

“…Overall, there is some evidence that plastic mulches could reduce the number of some natural enemies in the canopy and on the ground, but no studies have holistically tested the nontarget effects of plastic mulches on arthropods. Further, since plastic mulches are an effective management practice for the invasive pest D. suzukii (McIntosh et al, 2021(McIntosh et al, , 2023, it is critical to evaluate how they impact natural enemies of D. suzukii including Araneae, Carabidae, Chrysopidae, Dermaptera, Formicidae, Gryllidae, Hymenoptera, Nabidae, Orius spp., and Staphylinidae (Lee et al, 2019).…”