Observations on an introduced bud scale, Physokermes hemicryphus (Homoptera: Coccidae), infesting Norway spruce in Idaho

Abstract

An introduced bud scale on Norway spruce (Picea abies (L.) Karst. (Pinaceae)) in Idaho, formerly thought to be Physokermes piceae Schrank (Homoptera: Coccidae), is identified as Physokermes hemicryphus (Dalman). Secondary lateral branches of infested Norway spruce become pendent as a result of growing abnormally in length relative to diameter. The scale reproduces by parthenogenesis in North America; no male is known there. Mature females in situ resemble a branch bud. An average of 2.2 females occurred per infested node. They grew larger in late May, at which time they protruded visibly from beneath branch bud scales of the previous year and became immersed in their secreted honeydew. At maturity, females contained a prolific number of eggs (290–858). The eggs hatched into nymphs within the rigid exoskeleton of the dead female in late June. Nymphs emerged during July and migrated distally along a branch. They overwintered as second (final) instars attached to needles or beneath bud scales at the branch node from which the current-year terminal emanated. Four species of hymenopterous parasites were reared from adult scales. Of these, Americencyrtus sp. (Hymenoptera: Encyrtidae) was most abundant. It parasitized a majority of first instar nymphs but allowed them to develop to maturity the following spring before destroying their embryonic eggs and emerging in synchrony with appearance of nymphs of unparasitized females.