Which pest is commonly associated with grapes along with the Western grape leafhopper?

The pest commonly associated with grapes alongside the Western grape leafhopper is Erythoneura variabilis, which is known as the variegated leafhopper. This insect is significant in grape production because it feeds on the sap of grapevine leaves, leading to stress in the plants and potential damage to the fruit development. Its impact on grapevines often coincides with the presence of other pests, such as the Western grape leafhopper.

While other options represent pests or organisms that can affect grapevines, they do not share the same direct relationship or commonality with the Western grape leafhopper as Erythoneura variabilis does. For example, Pseudococcus comstocki, also known as the Comstock mealybug, primarily affects fruit crops but does not typically share the same habitat or association with grapevines as leafhoppers do. Pythopthora spp. refers to a group of fungi that cause root rot diseases, which is more disease-related than an insect pest relationship, while Planococcus ficus (the vine mealybug) may affect grapes but is not as commonly linked to the leafhopper as Erythoneura variabilis is. Thus, the correct answer reflects the specific association between this insect