Effect of Various Organic Mulches on Aphids, Their Predators, and Potato Virus Transmission

Potato virus Y (PVY) and potato leafroll virus (PLRV) are two viruses of major economic importance in potato cultivation. Several studies have demonstrated that the transmission of non-persistently transmitted PVY can be reduced through the use of straw mulch. However, little is known about the impact of other mulch materials and their influence on persistently transmitted PLRV. The impact of triticale/vetch, grass/clover, grass silage, and straw mulch was thus investigated in five field trials. Aphid flight activity was monitored using yellow water traps, and vector pressure was calculated based on species-specific relative efficiency factors. The occurrence of aphids and their predators on potato plants were assessed by visual counts. Harvested tubers were tested for their virus incidence for both PVY and PLRV. The results demonstrated that all mulch treatments significantly reduced aphid landings by 30-75% compared to the unmulched control, with the greatest reduction observed for Myzus persicae. Consequently, PVY vector pressure was substantially lower in mulched plots. Mulching with triticale/vetch, grass/clover, and straw significantly decreased PVY incidence by up to 75%. However, the overall incidence of PLRV was too low to make a conclusive statement about the effect of mulch on PLRV transmission. Aphid abundances and numbers of aphid predators on the plants were generally lower in mulched plots. These results demonstrate that organic mulches can be an effective cultural control measure against aphid-transmitted potato viruses, as they disrupt vector landing early in crop development and potentially reduce within-field spread.