Spruce sawfly

Pikonema is a genus of sawflies within the family Tenthredinidae that specifically targets spruce trees. These insects are significant defoliators, capable of causing extensive damage to both natural forests and managed ornamental conifer landscapes by feeding on foliage.

The primary hosts of this pest are various spruce species, including Norway spruce and blue spruce. The larvae are notorious for their voracious feeding habits, which can lead to significant needle loss, weakened tree health, and, in cases of severe infestation, mortality of the host plant if left unmanaged.

The life cycle typically spans one to two generations per year, depending on the environmental temperature. The pest overwinters as a prepupa within a cocoon located in the duff or upper soil layers beneath the host tree. Once the spring temperatures rise, the adults emerge to mate and lay eggs into the needles of the current year's growth.

Larval feeding patterns are highly characteristic of the species. Early-instar larvae often feed in groups, consuming parts of the needle tissue, while later stages devour entire needles, leaving only the central vascular structures behind. This defoliation reduces the tree's photosynthetic capacity, leading to visible chlorosis and eventual branch dieback.

Effective management requires an Integrated Pest Management (IPM) approach. Regular scouting for early signs of infestation is crucial during the spring season. Chemical control options include the targeted application of registered insecticides when larvae are at their most vulnerable stage, while biological controls, such as encouraging natural predators, provide a sustainable long-term solution.