Pine sawfly

Systematic position. The species Gilpinia frutetorum belongs to the order Hymenoptera and the family Diprionidae. It is a well-known needle-eating pest that specifically targets species of the genus Pinus, causing significant ecological and economic impact in coniferous forests and ornamental plantings.

Host plants and impact. The primary host is the Scots pine (Pinus sylvestris). The sawfly larvae are specialized defoliators. High population densities can lead to severe needle loss over large areas, which stresses the trees and reduces their annual growth rate, making them susceptible to secondary bark beetle attacks.

Biology and life cycle. This species undergoes a complete metamorphosis. They typically overwinter as prepupae inside tough, oval cocoons buried in the soil or leaf litter beneath the host tree. Adult sawflies emerge in the spring. Females use their saw-like ovipositors to insert eggs into the pine needles, which is the defining characteristic of this group.

Nature of damage. Young larvae usually feed on the edges of the needles, causing them to wither and curl. As the larvae mature, they consume the entire needle down to the sheath. Heavy infestations result in total defoliation of branches, which can cause crown thinning, stunted growth, and in repeated cases, the eventual death of the entire tree.

Control measures. Integrated Pest Management (IPM) is essential for controlling Gilpinia frutetorum. Monitoring the presence of cocoons and the emergence of adults helps in timing the applications. Effective strategies include:

• Application of biological control agents such as baculoviruses.
• Judicious use of systemic or contact insecticides during the early larval instar stages.
• Enhancing forest biodiversity to support natural predators like parasitic wasps and birds.
• Silvicultural practices, including the removal of heavily infested deadwood if necessary.