The first symptoms are downward curling of the leaf, associated with a bronzing of the interveinal tissue. The interveinal tissue becomes a paler green and eventually dies, giving rise to interveinal scorch. In the final stages the leaves wither to an ashy-gray color and fall. There may be a marginal scorch on the older leaves. A frequent pest on hops.
Winged aphids move to the top of the plant late in the spring.
Aphid populations may build very rapidly and if left uncontrolled may result in defoliation. A serious pest of hops grown in the warm interior valleys of the northwestern United States. Mite webs protect eggs and mobile mites from contact by sprays. Webbing is usually confined to the main interveinal areas of the underside of the leaf. Acaricides should be applied before webbing is extensive.