Effect of physical barriers on sweet potato weevil control

Two studies were conducted to determine the effect of physical barriers (black plastic, weed barrier and grass mulch) and a bare soil treatment on sweet potato weevil (SPW) infestation of "Viola" and "Sunny" sweet potato cultivars. Harvested roots were individually inspected and rated on a SPW damage index (DI) of 1-6 ( I - no damage, 6 - most severe damage). A mean damage index (MDI) was also calculated. All medium-sized storage roots with a DI rating _ 2 were considered as marketable yield. The yield of medium-sized roots for the "Sunny" cultivar was significantly higher under plastic mulch than on bare soil. The grass mulch treatment produced a higher percentage of storage roots rated DI-1 than plots with synthetic mulches (plastic or weed barrier). The grass mulch treatment also produced a higher percentage of medium-sized marketable roots than the weed barrier treatment. Sweet potatoes from the weed barrier plots had a higher MDI than those in the grass mulch plots. In the "Viola" study, the grass mulch treatment produced the highest total and marketable yields. The weed barrier treatment had a higher MDI, a lower percentage of roots rated DI-1 and a higher percentage of roots rated DI-6 than all the other treatments. These trials have demonstrated that grass mulch has more potential than weed barrier for controlling SPW.