**Pine Cone Beetles** (genus *Conophthorus*) are small bark beetles that attack the female **pine cones** of various pine species. These beetles are not considered forest-killing pests like the Pine Bark Beetle, but they are a major problem in pine seed orchards and nurseries. The larval feeding destroys the developing seeds within the cone, significantly reducing the viability and quantity of the pine seed crop, thus hindering commercial reforestation and tree breeding programs.
Taxonomy and Classification
Pine Cone Beetles belong to the family Curculionidae, subfamily Scolytinae. They undergo complete metamorphosis. They are highly specialized: *Conophthorus* species attack the cones only, while other scolytids attack the trunk, branches, or roots. The specific species present depends on the host pine species, such as the **White Pine Cone Beetle** (*C. coniperda*).
Physical Description
Adult Pine Cone Beetles are small, dark brown or black, cylindrical beetles, typically less than $1/8$ inch long.
The most important signs are found on the cones:
- **Entrance Hole:** A tiny entrance hole near the base of the cone.
- **Resin Mass:** A tell-tale droplet of hardened, white-yellow pitch (resin) often covers the entrance hole.
- **Internal Damage:** The interior of the cone is hollowed out, packed with frass (boring dust), and the scales may appear prematurely browned or wilted. The entire cone often drops prematurely.
Distribution and Habitat
Pine Cone Beetles are found wherever their specific pine hosts are grown. Their habitat is restricted to the developing cones of the pine tree canopy. They are most damaging in areas dedicated to seed production, where cone quantity and quality are prioritized.
Behavior and Damage
The beetle typically has one generation per year. It overwinters as an adult in the cone axis, soil, or needle litter.
In spring, the adult female bores into a newly developing female cone (usually in the second year of its development) to feed and lay eggs. The boring action and the subsequent feeding by the larvae girdle the core of the cone, stopping its development. The entire cone, containing the developing larva, often drops from the tree prematurely, usually by mid-summer. The larvae complete development and pupate within the destroyed cone.
The damage causes severe losses:
- **Seed Crop Failure:** Up to 90% of a valuable seed crop can be destroyed by heavy infestations.
- **Premature Cone Drop:** The most visible sign of attack is the premature shedding of small, damaged cones on the ground.
Management and Prevention
Control is concentrated on protecting the cones, as the tree’s health is not usually at risk.
- **Sanitation:** Collecting and destroying all fallen cones during the summer eliminates the developing larvae before they can overwinter.
- **Chemical Protection:** The only highly effective means of control in seed orchards is the precise application of **systemic insecticides** (often injected into the trunk or applied as a soil drench). The chemical moves into the developing cones, poisoning the beetles as they bore into the tissue. This must be done with tight regulatory oversight to prevent environmental contamination.
- **Pheromone Trapping:** Monitoring traps are used to determine the timing of the spring flight to guide chemical applications.
Conservation and Research
Pine Cone Beetles are managed as seed orchard and tree breeding pests. Research focuses on developing safer, highly targeted systemic chemical treatments and exploring the use of biological controls that might attack the cone beetle larvae within the protective cone structure.