Mass-Rearing Predators for Augmentation Biological Control of Balsam Woolly Adelgids in Fraser Fir Plantations

PROBLEM: Efforts to control balsam woolly adelgids (BWA) with conventional pesticides have failed, and natural enemy populations are too sparse to effectively control BWA, an exotic pest destroying natural and cultivated firs in the US, including Fraser firs in Christmas tree plantations. We propose to develop the technology for a diet-based mass rearing system for brown lacewings to control BWA in Fraser fir Christmas tree plantations. Efforts at control by cutting infested trees, applying pesticides and classical biological control have failed. In all of the failures of augmentation the problems were from errors in techniques (not enough predators applied, not matching seasons or life cycle, etc.) rather than inherent weaknesses of the augmentation model. Fraser fir is a native U.S. species, being ravaged by the balsam woolly adelgid (BWA) an exotic pest, and the adelgid, both in its natural range and in the extensive Christmas tree farming industry, which brings in nearly $100 million per year in North Carolina alone (Potter et al. 2005). Several million dollars per year are lost to BWA damage and cost of control, and more are threatened as this insect spreads (Potter et al. 2005). Old growth Fraser fir has been almost entirely destroyed (Dull 1988). It is the only fir species native to the Southern U.S. and a dominant species of the spruce-fir ecotype of the Southern Appalachians (Burns and Honkala 1990). These unique forests are popular recreational areas, including the Great Smoky Mountains National Park. In Christmas tree plantations, even light infestations can cause a loss of apical dominance, rendering the tree useless as a Christmas tree. Fraser fir is economically important to the people of the Southern Appalachians. In North Carolina, 5.5 to 6.0 million Christmas trees (over 98% Fraser fir) are harvested annually, which is the second largest Christmas tree harvest in the nation (Potter et al. 2005). PURPOSE: If brown lacewings could be mass-reared and made abundant enough for inoculation of individual infested trees, at a rate of 5-10 lacewing eggs per tree, BWA could be reduced in plantations below damaging threshold. To make such releases possible, a mass-rearing system based on a low cost artificial diet must be developed, and with such a diet, cost of reducing BWA populations could be less than pennies per tree. Such control would translate into prevention of loses of millions of dollars worth of trees per year. This Phase I will determine feasibility for developing a low cost diet and rearing technology and testing the laboratory reared predators on BWA infested Fraser firs in a greenhouse setting. Green and brown lacewings (Chysopidae and Hemerobiidae) in the natural habitats of BWA (European forests) have been shown to be quite effective in suppression of Adelges piceae (Szentkiralyi 2001), so there is a strong basis for optimism about the chances of large scale releases of lacewings being a key factor in BWA suppression. In contrast with natural forests Christmas tree plantations are, in all respects, parallel to orchards where augmentation biological control has been successful.