Competitive interactions among two specialist predators and a generalist predator of hemlock woolly adelgid, <i>Adelges tsugae </i>Annand (Hemiptera: Adelgidae)

Flowers, Robbie Wayne

Competitive interactions among two specialist predators and a generalist predator of hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae)

dc.contributor.author	Flowers, Robbie Wayne	en
dc.contributor.committeecochair	Salom, Scott M.	en
dc.contributor.committeecochair	Kok, Loke T.	en
dc.contributor.committeemember	Pfeiffer, Douglas G.	en
dc.contributor.committeemember	Mullins, Donald E.	en
dc.contributor.committeemember	Montgomery, Michael E.	en
dc.contributor.department	Entomology	en
dc.date.accessioned	2014-03-14T20:09:51Z	en
dc.date.adate	2006-04-26	en
dc.date.available	2014-03-14T20:09:51Z	en
dc.date.issued	2006-04-10	en
dc.date.rdate	2007-04-26	en
dc.date.sdate	2006-04-17	en
dc.description.abstract	Competitive interactions among two specialist predators, <i>Laricobius nigrinus</i> Fender (Coleoptera: Derodontidae) and <i>Sasajiscymnus tsugae</i> Sasaji and McClure (Coleoptera: Coccinellidae), and a generalist predator, <i>Harmonia axyridis</i> Pallas (Coleoptera: Coccinellidae), of hemlock woolly adelgid were evaluated using laboratory, field and video studies. The two specialist predators are part of a biological control program for <i>A. tsugae</i>, and the potential for competition among these species and previously established generalist predators is unknown. In laboratory studies of predator groups in Petri dish assays, the only significant negative effects from competition occurred among conspecifics, resulting in reduced net egg production by <i>L. nigrinus</i> and <i>H. axyridis</i> and reduced feeding by <i>H. axyridis</i>. In contrast, heterospecific combinations showed non-interference. In longer duration field studies of predator groups, held in branch enclosures, predator survival and feeding were not significantly affected by additional predators. Net reproduction was again significantly reduced by conspecifics, while heterospecifics showed non-interference for all predator responses. All predators reduced the number of <i>A. tsugae</i> nymphs of the next generation relative to no-predator controls; however, <i>L. nigrinus</i> had much greater impact overall due to the large number of progeny produced. Video studies revealed that predator behavior varied qualitatively and quantitatively by species, and did not appear to be coordinated temporally or spatially. All species exhibited continuous activity patterns that were punctuated by longer periods of rest. The specialist predators were more selective of feeding and oviposition sites, and rested at more concealed locations than <i>H. axyridis</i>. Conspecifics significantly altered the time allocated to specific behaviors for <i>L. nigrinus</i> and <i>H. axyridis</i>, resulting in reduced predator effectiveness due to increased searching and decreased feeding and oviposition. All predator groups maintained a high degree of spatial separation relative to assay size, suggesting that chemical or tactile cues may be used to regulate their distributions. Overall, these studies suggest that the three predator species will be compatible in this system. Management implications include using multiple-predator species combinations over single-species for biological control of <i>A. tsugae</i> and implementing low-density releases to reduce the potential negative effects of intraspecific competition.	en
dc.description.degree	Ph. D.	en
dc.identifier.other	etd-04172006-090625	en
dc.identifier.sourceurl	http://scholar.lib.vt.edu/theses/available/etd-04172006-090625/	en
dc.identifier.uri	http://hdl.handle.net/10919/26932	en
dc.publisher	Virginia Tech	en
dc.relation.haspart	Dissertation.pdf	en
dc.relation.haspart	Extensive_Searching.mov	en
dc.relation.haspart	Intensive_Searching.mov	en
dc.relation.haspart	Resting.mov	en
dc.relation.haspart	Feeding.mov	en
dc.relation.haspart	Oviposition.mov	en
dc.rights	In Copyright	en
dc.rights.uri	http://rightsstatements.org/vocab/InC/1.0/	en
dc.subject	Harmonia axyridis	en
dc.subject	Sasajiscymnus tsugae	en
dc.subject	Laricobius nigrinus	en
dc.subject	Hemlock woolly adelgid	en
dc.subject	Predator Interactions	en
dc.subject	Biological Control	en
dc.title	Competitive interactions among two specialist predators and a generalist predator of hemlock woolly adelgid, <i>Adelges tsugae </i>Annand (Hemiptera: Adelgidae)	en
dc.type	Dissertation	en
thesis.degree.discipline	Entomology	en
thesis.degree.grantor	Virginia Polytechnic Institute and State University	en
thesis.degree.level	doctoral	en
thesis.degree.name	Ph. D.	en