The White Pine Weevil’s Life Cycle – Ray Asselin

Tree architecture is affected by many factors. Genetics is a major determinant. Hundreds of genes coordinate to determine the stature of a tree. Conifers have strong apical dominance in their growth and plant hormones such as the auxin play a lead role in its maintenance. When the apical dominance is lost due to loss of the apical meristem located at the top of shoot tip the branching pattern of a tree changes.

Apical meristem can be lost due to physical damage by strong winds, treefalls or frost. Herbivores may simply browse the apical meristem or as shown in this documentary pests and disease may disrupt this important tissue.

Here filmmaker Ray Asselin shows how the white pine weevil (Pissodes strobi) causes shoots of the eastern white pine (Pinus strobus) to suffer. Most adult weevils, have a long snout-like beak from which small antennae protrude. They look like miniature cute anteaters. Using their long snout adult insects feed and females drill holes for oviposition. The tree on the other hand may loose its dominant growth axis due to weevil damage and is forced to produce new ones that will compete with each other for dominance.

Conifers have a potent chemical defensive strategy that has been quite successful for hundreds of million years. Resin ducts can become a death trap for many insects that want to take a bite from those trees. Eastern white pine resin can be effective against the weevil larvae. Resin is a complex mixture of compounds produced by the secondary metabolism of the tree. Secondary metabolism provides all the remedies to solve problems such as the weevil infestations or attack from pathogenic fungus or even climate control by formation of hygroscopic biogenic aerosols such as the characteristic 10 carbon containing alpha-pinene molecule that serve as seeds for low altitude cloud formation. As the biological arms race between host and parasites continue the ingredients of the secondary metabolism evolve.