Landscapes with higher crop diversity have lower aphid species richness but higher plant virus prevalence

Abstract

Diversifying agricultural systems by growing more than one crop species in an area can decrease pest and disease pressure and increase crop yields. However, there is a lack of information on how crop diversity at larger spatial scales influences pest and disease pressure. Here, we investigated how landscape-scale crop diversity affects aphid vector communities and prevalence of non-persistently transmitted potato virus Y (PVY). To test the influence of landscape-scale crop diversity on PVY prevalence and aphid communities, we conducted a field study during the 2020 and 2021 field seasons in the San Luis Valley, Colorado, where we quantified aphid communities and PVY incidence at multiple sites. We then determined the association between aphid species richness and abundance and PVY incidence with landscape variables (crop diversity metrics and percentage cover of crop species) within 1, 2 and 3 km buffers from study sites. Higher crop diversity (measured as Shannon Diversity Index) led to decreased aphid species richness at a 3 km buffer in the 2021 field season. We only detected a positive association between percentage of alfalfa crop cover and aphid species richness in 2020 and aphid abundance in 2021 within a 1 km buffer. Higher crop diversity led to increased PVY incidence at a 2 km buffer in 2021 and 3 km buffer in 2020 and 2021. At a 3 km buffer in 2021, we found a positive influence of crop species richness on PVY incidence and a negative influence of crop species evenness on PVY incidence. Also in 2021, we found a positive influence of percentage of potato (virus host) on PVY incidence and a negative influence of percentage of barley (virus non-host) on PVY incidence. Synthesis and applications. In summary, we found that landscape-scale crop diversity impacts plant virus prevalence at spatial scales of >1 km. This suggests that potato growers could reduce PVY prevalence by geographically isolating potato fields from other potato or other PVY hosts. Crop diversity had a negative influence on aphid vector communities, so growers could reduce risk of virus spread by aphid vectors by using certified potato seed in a diversified landscape.