coniferarum A Potential Biological Control Agent for HWA�

Authors: Molly Darr and Dr. Scott Salom� Source: Department of Entomology, Virginia Tech � Background: Scymnus (Pullus) coniferarum Crotch (Coleoptera: ) is a predator of hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae). It was first described in 1874 from specimens collected off of pine in California. More recent descriptions place this predator in the Subfamily , Tribe and subgenus Pullus Mulsant 1846 (Gordon 1985). Species in the Scyminae subfamily USDA, 2012 are prey-specific, and feed on Adelgidae in the order Hemiptera. � Description:  S. coniferarum is a small lady , about 2 mm in length that is clothed in fine, short pubescence with a black head and pronotum and reddish-yellow brown elytra that is piceous along the suture and at the base (Fig. 1). The larvae are recognized by a covering of white woolly wax, which is especially conspicuous in the last instar (Fig. 2). The wax has long filaments in six longitudinal rows with the filaments discernable clear to the base (Whitehead 1967). Female morphology is similar to male, except apex of fifth sternum was denoted as ‘evenly rounded’ and the pronotum can be entirely yellowish brown (Fig. 3) (Montgomery et al. 2010; Gordon 1985). Figure 1: Adult S. coniferarum � feeding on HWA eggs.

A B C D

Figure 2: S. coniferarum lifestages: (A) eggs on an eastern hemlock (T. canadensis); (B) larva feeding on an HWA crawler; and (C) pupa. Figure 3: Teneral S. Life History: coniferarum adult. The univoltine life cycle of S. coniferarum appears to be synchronous with the life cycle of HWA. S. coniferarum adults are present, and presumably feed on HWA sistens and the eggs of sistens during the late fall and winter season. In severe winter weather, the adults are known to seek protection by hiding in bark crevices on the bole of the tree (McDonald, 2010).

In the laboratory setting, oviposition of S. coniferarum begins in early April when HWA sistens are nearing the end of its oviposition period and progrediens eggs begin hatching. In the same study, S. coniferarum oviposition ends in mid-May when 1st – 3rd instar progrediens are present (USDA 2012). The fecundity of S. coniferarum females and oviposition length is still unknown. The larval stage has been observed feeding on HWA progrediens from May to June, and will most likely continue to feed on the eggs laid by the progrediens generation into July (Montgomery et al. 2011; Kohler et al. 2008). Instead of completing aestivation in the soil, S. coniferarum pupates near its host or under tree bark for an undetermined duration of time. The precise timing of adult emergence remains unknown.

September 9, 2014 �

Scymnus coniferarum A Potential Biological Control Agent for HWA� Range:  The known native geographic range of S. coniferarum is western North America (Gordon 1985). Specimens have been collected from various species of pines in British Columbia, Arizona, California, Colorado, Idaho, Nevada, New Mexico, Oregon, South Dakota, Utah, and Wyoming (Gordon 1976) (Fig.4). Recently, several hundred specimens have been collected from western hemlock in Washington State T.#caroliniana# (Montgomery et al. 2009, McDonald 2010). Therefore, it is not likely S.#coniferarum# T.#mertensiana# specific to HWA, but to other adelgids as well. The distribution pattern T.#heterophylla# T.#canadensis# of S. coniferarum is unusual and likely unnatural; perhaps due to artificial transportation through the shipment of nursery stock across Figure 4: (A) Collection sites of S. coniferarum the country (Whitehead 1967). and distribution of Tsuga spp. In North America. � Biological Control: Neither imported nor native natural enemies have held HWA below injurious levels in the eastern US. However, such a predator complex is thought to exist in the Pacific Northwest, part of HWA’s native range. Recently, S. coniferarum has been observed feeding on HWA in close association with Laricobius nigrinus Fender in the Seattle area. While L. nigrinus and S. coniferarum maintain similar densities through the fall and winter, as L. nigrinus larvae move into the soil for aestivation, S. coniferarum completes development on the tree and has been observed feeding through June (McDonald 2010).

The seasonal occurrence of S. coniferarum and L. nigrinus, as well as their prey, HWA, in the Seattle, Washington area is shown in Table 1. Other information indicates that HWA eggs are also present during July in western Washington (Kohler et al. 2008). In early October, S. coniferarum adults are more abundant on western hemlock than adults of L. nigrinus, but L. nigrinus is about 50% more abundant by the end of the month. Larvae of L. nigrinus appear in March and complete development by mid-May. S. coniferarum larvae appear in May and probably continue to feed on the progrediens and their sistens eggs into July. Thus, only S. coniferarum is feeding on the HWA sistens eggs that are produced in June and July. Table 1: Seasonality of S. coniferarum and L. nigrinus on western hemlock Future Directions: 78,(0 $ $$$$$$$$$$$96($$$$$$$:84$$$$$$$$$;*6$$$$$$$$$<2,$$$$$$$$$=*>$$$$$$$$723$$$$$$$$#/3$$$$$$$$72-$$$$$$$$$<&,$ As the widespread devastation of HWA- !"#$#%&'()$ infested hemlock in the eastern United States !"#$*++)$ continues, consideration of additional !"#$,-./0)$ biological control agents to build a more robust 1,$2%&'()$ 1,$'2342*$ and effective predator complex is a logical 56$2%&'()$ approach to take. 56$'2342*$ At this time, essential details of S. coniferarum development, predation, fecundity and host preference are lacking. In order to assess the potential of this predator as a Predator at low density Predator at high density biological control agent of HWA, it is critical that its biology and predation attributes be Progrediens investigated. Such studies are currently ongoing. Sistens References: Gordon, R.D. 1976. The Scymnini (Coleoptera: Coccinellidae) of the United States and Canada: Key to genera and revision of Scymnus, and . Bulletin of the Buffalo Society of Natural Sciences 28: 66-68. Gordon, R.D. 1985. The Coccinellidae (Coleoptera) of America North of Mexico. Journal of the New York Entomological Society 93: 1-912. Kohler, G. R., V. L. Stiefel, K. F. Wallin, and D. W. Ross. 2008. Predators associated with the hemlock woolly adelgid (Hemiptera: Adelgidae) in the Pacific Northwest. Environmental Entomology 37: 494-504. McDonald, R.D. 2010. Key Cues and Factors for Improving HWA Predator Recovery Efforts. In: B. Onken and R. Rearden [eds.], Fifth Symposium on Hemlock Woolly Adelgid in the Eastern United States. USDA Forest Service, Asheville, NC. FHTET-2010-07. Montgomery, M.E., R. McDonald and L. Schwartzberg. 2009. Scymnus (Pullus) coniferarum (Coleoptera: Coccinellidae): An Adelgid Predator Native to the Western United States. McManus, Katherine A; Gottschalk, Kurt W., eds. Proceedings. 20th U.S. Department of Agriculture interagency research forum on invasive species 2009; 2009 January 13-16; Annapolis, MD. Gen. Tech. Rep. NRS-P-51. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 89. Montgomery, M.E. and R. D. McDonald. 2010. Host Preferences of Scymnus (Pullus) coniferarum: An adelgid predator. Pp. 173-176. In: B. Onken and R. Reardon [eds.], Fifth Symposium on Hemlock Woolly Adelgid in the Eastern United States, Ashville, NC USDA Forest Service. FHTET-2008-10. Whitehead, V.B. 1967. The validity of the higher taxonomic categories of the Tribe Scymnini (Coleoptera: Coccinellidae). Ph. D. Thesis, University of California, Berkley. 215p. USDA APHIS. 2012. Release of the Predatory Beetle Scymnus coniferarum (Coleoptera: Coccinellidae), for Biological Control of the Hemlock Woolly Adelgid (Adelges tsugae) in the Eastern United States. Environmental Assessment.