Balsam woolly adelgid (Dreyfusia piceae) (Ratzeburg)

Origin
Native to Europe.

Life Cycle
The aphid has two generations per year, and occasionally three in the southern Appalachians. Eggs of the first generation hatch in late June and July, followed by a second-generation in September and October. The "crawler" is the only mobile stage in the adelgid's life cycle. When a crawler begins feeding, it transforms into a first instar nymph and becomes stationary. Reproduction is parthenogenic, with each female laying up to 200 eggs. The adelgid overwinters as a first instar nymph and continues its development in the spring when the host tree starts its annual growth cycle.

Distribution
The balsam woolly adelgid was introduced from Europe to North America around 1900. In the west, they have been found only in northern Idaho, but may occur in Montana. In the east, it has become an important pest of true firs and is established throughout the Fraser fir type in the southern Appalachians. The balsam woolly adelgid attacks all true fir Abies species, the most susceptible being Balsam Fir Abies balsamea and Fraser Fir Abies fraseri. European fir species such as Silver Fir Abies alba, having evolved alongside the insect, show greater resistance, but are not immune. It also causes considerable damage to the Fraser fir Christmas tree industry.

Control Efforts
In forest situations, silvicultural and management techniques can be used to reduce adelgid populations and damage. Tree stress may be minimized by thinning overstocked stands, by fertilizing sites of poor nutrient quality (although some nitrogenous fertilizers such as urea can increase insect survival), and by replanting or encouraging more tolerant tree species and varieties. A damage-hazard rating system based on-site and stand characteristics associated with severe adelgid damage can be used to aid in management decisions. The main variables used in the system are site elevation, soil moisture regime, percent Balsam Fir by basal area, total basal area of Balsam Fir, and stand age. In general, lower elevation, dry sites with over 40% Balsam Fir, and over 45 years old, are most susceptible. Trees over 25 and under 45 years old are moderately susceptible, and trees under 25 years old are least susceptible. In Christmas tree plantations, if only a few trees are infested, roguing or burning those trees should be sufficient for managing the pest.
 
Chemical control is effective, but extremely costly. Thus it's usually limited to high-value resources such as recreation areas, seed sources, and shade, ornamental, and Christmas tree plantings. For chemical recommendations, please refer to the latest edition of the pest management guidelines for your region.
 
https://wiki.bugwood.org/Adelges_piceae
 

Resources

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• Insects and Diseases of Trees in the South - USDA Forest Service
• Global Invasive Species Database - Invasive Species Specialist Group

Invasive Listing Sources

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• Michigan’s Invasive Species Watch List
• Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
• South Carolina Plant Pest List
• To be proposed for MISC
• West Virginia Invasive Species Strategic Plan and Volunteer Guidelines 2014

References

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Common Name Reference: Bosik, J. J. Common Names of Insects and Related Organisms 1997. Lanham, MD: Entomological Society of America (ESA), 1997. 232 pp.

Scientific Name Reference: R.W. Poole and P. Gentili, Nomina Insecta Nearctica. 1996. Nomina insecta nearctica: a checklist of the insects of North America. Vol. 1-4. Rockville (MD): Entomological Information Services. Available at URL: http://www.nearctica.com/nomina/main.htm