Browsing by Author "Salom, Scott M."
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- 2021 Horticultural and Forest PMG - AuthorsAskew, Shawn D.; Baudoin, Antonius B.; Bergh, J. Christopher; Chamberlin, Lori; Dary, Eric R.; Del-Pozo, Alejandro; Derr, Jeffrey F.; Frank, Daniel; Hansen, Mary Ann; Hong, Chuan X.; Johnson, Charles S.; Laub, Curtis A.; McCall, David S.; Nita, Mizuho; Parson, Rachel; Peer, Kyle; Pfeiffer, Douglas G.; Richardson, Robert J.; Salom, Scott M.; Schultz, Peter B.; Wilson, James (Virginia Cooperative Extension, 2021-02-12)Horticultural and Forest Crops 2021 Author Contact List
- 2021 Horticultural and Forest PMG - Pests of Forestry and Christmas TreesDay, Eric R.; Salom, Scott M.; Chamberlin, Lori; Peer, Kyle; Hansen, Mary Ann; Derr, Jeffrey F. (Virginia Cooperative Extension, 2021-02-12)This is a chapter from the 2021 Horticulture and Forest Pest Management Guide. The Virginia Pest Management Guide (PMG) series lists options for management of major pests: diseases, insects, nematodes, and weeds. These guides are produced by Virginia Cooperative Extension and each guide is revised annually. PMG recommendations are based on research conducted by the Research and Extension Division of Virginia Tech, in cooperation with other land-grant universities, the USDA, and the pest management industry.
- 3D X-ray analysis of the subterranean burrowing depth and pupal chamber size of Laricobius (Coleoptera: Derodontidae), a specialist predator of Adelges tsugae (Hemiptera: Adelgidae)Hillen, Ashleigh P.; Foley, Jeremiah R.; Salcedo, Mary K.; Socha, John J.; Salom, Scott M. (Oxford University Press, 2023-05-01)The non-native hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae), has caused a significant decline of eastern hemlock, Tsuga canadensis L. (Pinales: Pinaceae), and Carolina hemlock, Tsuga caroliniana Engelmann (Pinales: Pinaceae), in eastern North America. Biological control of HWA has focused on the use of 2 Laricobius spp. (Coleoptera: Derodontidae), natural predators of HWA, which require arboreal and subterranean life phases to complete their development. In its subterranean phase, Laricobius spp. are subject to abiotic factors including soil compaction or soil-applied insecticides used to protect hemlock from HWA. This study used 3D X-ray microcomputed tomography (micro-CT) to identify the depth at which Laricobius spp. burrows during its subterranean lifecycle, characterize pupal chamber volume, and determine whether soil compaction had a significant effect on these variables. The mean burrowing depth in the soil of individuals was 27.0 mm ± 14.8 (SD) and 11.4 mm ± 11.8 (SD) at compaction levels of 0.36 and 0.54 g/ cm3, respectively. The mean pupal chamber volume was 11.15 mm3 ± 2.8 (SD) and 7.65 mm3 ± 3.5 (SD) in soil compacted at 0.36 and 0.54 g/cm3, respectively. These data show that soil compaction influences burrowing depth and pupal chamber size for Laricobius spp.This information will help us better identify the effect of soil-applied insecticide residues on estivating Laricobius spp. and soil-applied insecticide residues in the field. Additionally, these results demonstrate the utility of 3D micro-CT in assessing subterranean insect activity in future studies.
- Arthropod assemblages on longleaf pines: a possible link between the red-cockaded woodpecker and groundcover vegetationTaylor, Thomas Brandon (Virginia Tech, 2003-02-26)Little is known about arthropod communities inhabiting longleaf pines in the southeastern United States. This information is of particular importance because arthropods serve as the food base for the federally endangered red-cockaded woodpecker (RCW). In a recent study, this arthropod community has been suggested to be the mechanism by which RCW reproductive success is linked to the groundcover composition of the forest (which is a reflection of the forest's fire history). This is possible because it has been shown that much of the arthropod community found on longleaf pines originates from the forest floor. If the arthropod community is the link between the ground cover and the RCWs' reproductive success then higher amounts of arthropods should be found in areas with groundcover that is indicative of frequent burning. I conducted a one year study at three sites containing RCWs to determine whether the ground cover of the forest influences the abundance and mass of the arthropod communities on longleaf pines. I focused on impacts of groundcover on arthropods by controlling for tree species, tree age, soil type, hardwood midstory density, and overstory basal area. My results show that arthropod biomass was positively and significantly correlated to the percent coverage of herbaceous and graminoid vegetation and was negatively and significantly correlated to the percent coverage of woody vegetation. Arthropod biomass and abundance was also observed to vary seasonally with a peak occurring during spring and summer. Additionally, prescribed fire was not found to have a negative short-term impact on arthropod biomass.
- Assessing Eucryptorrhynchus brandti as a Potential Carrier for Verticillium albo-atrum from Infected Ailanthus altissimaSnyder, Amy Lynn (Virginia Tech, 2011-05-20)Significant mortality of the invasive tree of heaven (TOH), Ailanthus altissima (Mill.) Swingle, was first observed in Pennsylvania in 2002 to be caused by an apparently host-specific strain of Verticillium albo-atrum Reinke & Berthold, a soil-borne, vascular wilt fungus. A limited survey conducted in Virginia revealed two sites where TOH stands were infected with V. albo-atrum. A virulence test confirmed that fungal isolates from both states were found to be highly pathogenic on TOH, killing all inoculated seedlings in 9 weeks. After overwintering, 11% (n = 37) of TOH root sections tested positive for V. albo-atrum, although the origin of the colonies was not identified. The pathogenicity of this pathogen suggests that it could be used together with host-specific insects for the biological control of TOH. A host-specific herbivorous weevil from China, Eucryptorrhynchus brandti Harold (Coleoptera: Curculionidae) that has been extensively studied as another potential biological control agent for TOH is currently pending quarantine release. Quarantine experiments were conducted to test different forms of transmission with E. brandti and V. albo-atrum simultaneously. In one experiment, 75% (n = 32) of adult E. brandti transmitted V. albo-atrum to TOH seedlings after walking on an actively growing culture and feeding on infected plant material. In another study after feeding on infected TOH stems for 24, 48 and 72 h, respectively, 16.7% (n = 120), 15.0% and 12.5% of adult E. brandti ingested and passed viable V. albo-atrum propagules into feces. Surviving weevils (83%, n = 20) overwintering in infested potting mix carried viable V. albo-atrum propagules externally. In addition, all weevil progeny that emerged from infected TOH billets appeared to be as healthy as weevils reared from non-infected billets and wild parents from China. Results from these laboratory studies indicate E. brandti has the ability to spread V. albo-atrum from tree to tree in a laboratory setting.
- Assessing performance and compatibility of three Laricobius species as predators of hemlock woolly adelgid, Adelges tsugaeStory, Heather Marie (Virginia Tech, 2010-05-19)Predation, egg production and survivorship of Laricobius nigrinus Fender, L. rubidus, LeConte, and L. osakensis Montgomery and Shiyaki (proposed), predators of hemlock woolly adelgid, Adelges tsugae, Annand, were investigated in the laboratory and in the field. In individual assays, L. rubidus oviposited fewer eggs than either L. nigrinus or L. osakensis. In assays containing congeneric or conspecific groups of adult Laricobius, L. osakensis preyed upon the greatest number of ovisacs. When all three species were together, the numbers of ovisacs preyed upon were similar to the mean of all three individual species. Adult predators fed on few eggs and did not exhibit any species preference. The numbers of A. tsugae ovisacs fed upon did not differ significantly by groups of congeneric or conspecific Laricobius larvae. Laricobius adults and larvae had high survival rates throughout all experiments. In the field, predators were enclosed in sleeve cages with both high (> 120 ovisacs) and low (< 90 ovisacs) A. tsugae densities for 1 wk. All branches with caged beetles had significantly greater numbers of ovisacs preyed upon than branches caged without beetles. No differences in predation or egg production were found among the conspecific and congeneric groupings. Predation was uniformly higher at the high prey-density than at the low prey-density. Survivorship among predators did not differ significantly at either prey density. Results from both laboratory and field experiments suggest that these species are able to co-exist and can be in the same location for biological control of A. tsugae.
- An Assessment of the Potential Impacts of Emerald Ash Borer (Agrilus planipennis Fairmaire) on Virginia's Municipal Street TreesWright, Gordon Tyler (Virginia Tech, 2011-07-22)Emerald ash borer (Agrilus planipennis Fairmaire) (EAB) is an invasive, wood-boring beetle (Coleoptera: Buprestidae) introduced unintentionally to the United States from East Asia that infests and eventually kills native ash trees (Fraxinus spp.). First detected near Detroit, Michigan in 2002, EAB had spread to fifteen U.S. states by 2011, killing an estimated 50 million ash trees along the way. EAB was first discovered in Virginia in 2003 and re-infested the state in 2008, raising concerns over impacts that the invasive pest might have on municipal urban forests and street trees. Despite these concerns, little is known about native ash abundance in Virginia's urban forests; as a result, potential EAB impacts have been difficult to project. In this study, street tree assessments were conducted in fourteen Virginia municipalities using i-Tree Streets®, which is a software program developed by the U.S. Forest Service that uses field inventory data to estimate street tree abundance and composition along with the quantity and monetary worth of functional benefits provided by these street trees. In addition to estimating potential losses of functional benefits provided by native ash street trees, information obtained from Virginia Dept. of Transportation was used to estimate the potential cost of removing these trees from the street side. The assessment indicated that there are about 4,600 native ash street trees in the fourteen studied localities and that native ash species comprise about 2% of municipal street tree populations on average. The highest relative abundance of native ash was found in Winchester City (5.8% of all street trees) whereas Richmond City had the greatest number of native ash street trees (estimated at 1,417). In terms of species importance (which accounts for both the relative abundance and relative size of trees in the population), only two localities (City of Roanoke and Town of Abingdon) had a native Fraxinus species among the top-five most important street tree species in the locality. In contrast, every municipality had at least one Acer species among the top-five, and eight of fourteen localities had at least one top-five Quercus species. Native ash street trees in the studied localities were estimated to provide functional benefits (energy conservation, stormwater mitigation, air pollution abatement, carbon sequestration, and aesthetic contributions) valued at over $535,000 annually, or roughly $38,000 per locality. In addition, carbon stored in these trees (about 17 million kilograms) was valued at nearly $277 thousand. The total estimated cost of removing lost ash trees was estimated at nearly $1.75 million, averaging about $124,000 for each municipality, and replacing the canopy cover and basal area provided by existing native ash street trees would exceed $17 million. In total, the studied localities would incur a gross financial impact of about $20.26 million due to losses of functional benefits and structural assets provided by native ash street trees.
- Balsam Twig AphidDay, Eric R.; Salom, Scott M. (Virginia Cooperative Extension, 2015-03-03)This home pest fact sheet describes the plants attacked, description of damage, identification, life cycle, control and remarks on the balsam twig aphid, Mindarus abietinus.
- Balsam Woolly AdelgidSalom, Scott M.; Day, Eric R. (Virginia Cooperative Extension, 2015-06-24)Describes the balsam wooly adelgid, its distribution and hosts, life history, damage to trees, and discusses methods of control.
- Balsam Woolly AdelgidSalom, Scott M.; Dellinger, Theresa A.; Day, Eric R. (Virginia Cooperative Extension, 2021-03-01)A fact sheet about balsam woolly adelgid, a pest of firs in Virginia.
- Bean Leaf Beetle: Impact of Leaf Feeding Injury on Snap Beans, Host Plant Choice and Role as a Vector of Bean Pod Mottle Virus in VirginiaCassell, Meredith Edana (Virginia Tech, 2011-04-12)The bean leaf beetle (BLB), Cerotoma trifurcata (Forster) (Coleoptera: Chrysomelidae), is a pest of commercially produced legumes in eastern Virginia. Field cage and manual-defoliation studies were conducted in Virginia to determine an economic impact of BLB. In the manual-defoliation study, snap bean plants had significant yield loss when > 25% of leaf area was removed. In the field cage experiments, I was unable to establish beetle densities per plant to impact yield. Host plant selection by BLB was done in laboratory and field studies with snap bean, lima bean, and soybeans. Laboratory studies showed that BLB preferred snap bean and lima bean over soybean. Field studies did not showed no preference. A survey was conducted on the Eastern Shore of Virginia determine the epicenter of BPMV. Soybean leaves and beetles were collected and assessed for BPMV by ELISA or TBIA. Beetles at the ESAREC were BPMV-positive upon emergence from overwintering sites, but the virus load was low when tested by ELISA. This suggests acquisition of virus from a source other than infected cultivated legumes. To find the potential inoculum sources of BPMV in eastern Virginia, leguminous weeds and perennial weeds were tested for BPMV. Four weed species gave BPMV-positive tissue blots including: Oxalis stricta, Rumex acetosella, Trifolium pretense, and Trifolium repens. Insecticidal seed treatment of thiamethoxam on soybean seeds was evaluated to test the efficacy. Leaf area eaten and beetle mortality was measured. The thiamethoxam seed treatment protected soybean seedlings from beetle feeding through the V2 stage of growth.
- Behavior and daily activity patterns of specialist and generalist predators of the hemlock woolly adelgid, Adelges tsugaeFlowers, Robbie Wayne; Salom, Scott M.; Kok, Loke T.; Mullins, Donald E. (University of Arizona, 2007-08-14)The behavior and daily activity patterns of two specialist predators, Laricobius nigrinus Fender (Coleoptera: Derodontidae) and Sasajiscymnus tsugae, Sasaji and McClure (Coleoptera: Coccinellidae), and a generalist predator, Harmonia axyridis Pallas (Coleoptera: Coccinellidae), of hemlock wooly adelgid, Adelges tsugae (Hemiptera: Adelgidae), were examined using digital video recording in the laboratory...
- Biological control of the invasive Ailanthus altissima (tree-of-heaven) in Virginia using naturally occurring Verticillium wilt fungiBrooks, Rachel Keys (Virginia Tech, 2020-06-08)The invasive tree-of-heaven, Ailanthus altissima (Miller) Swingle, is widespread and damaging throughout North America. Verticillium wilt disease is emerging as a potentially exciting biological control option for this difficult to control tree. In Virginia, Verticillium nonalfalfae has been confirmed causing significant mortality to A. altissima, while V. dahliae is suspected to be present and causing lower levels of disease. Little else is known regarding these two fungal species in this state. The purpose of this research was to gain a better understanding of how Verticillium wilt impacts A. altissima and its potential as a biological control agent. We first confirmed V. dahliae's presence in Virginia and its pathogenicity to A. altissima using Koch's postulates. We then completed a regional field-inoculation experiment to show that V. nonalfalfae effectively kills and spreads to adjacent A. altissima, regardless of V. dahliae presence or other climate and stand variables. Additionally, we showed that V. dahliae causes lower levels of disease than V. nonalfalfae, and does not spread rapidly. Next, we surveyed all Virginia A. altissima stands known to be naturally infected with V. nonalfalfae to determine whether V. nonalfalfae persists long-term, that it considerably reduces A. altissima numbers, and that its local prevalence may be higher than initially suspected. However, we were unable to infect A. altissima seedlings using soil collected at these infested sites, suggesting that V. nonalfalfae's survival within field soil may be limited. Lastly, using paired A. altissima invaded-uninvaded sites, we found that A. altissima presence is associated with a decreased proportion of native plants and species in the woody and herbaceous understory, but not the germinable seedbank. Furthermore, we found that this impact on the woody understory appears to increase over time, supporting early management actions and helping us predict post-management restoration needs. We conclude that V. nonalfalfae has a high potential of successfully limiting A. altissima throughout Virginia, supporting its registration as a biopesticide.
- Biological Studies and Evaluation of Scymnus Coniferarum, a Predator of Hemlock Woolly Adelgid from Western North AmericaDarr, Molly Norton (Virginia Tech, 2017-06-07)The hemlock woolly adelgid (HWA), Adelges tsugae Annand, is an invasive pest of eastern hemlock, Tsuga canadensis (L.) Carriere and Carolina hemlock Tsuga caroliniana Englem. in the eastern United States. A newly reported beetle predator for HWA, Scymnus (Pullus) coniferarum Crotch (Coleoptera: Cocinellidae) preys on the pest in the western United States, and was approved for release in the eastern United States for the control of HWA. This research investigated the viability of S. coniferarum as a biological control agent of A. tsugae in the eastern United States, as well as the ecological dynamics between S. coniferarum and host prey species in its native range of western North America. In objective one, S. coniferarum predation, reproductive potential, and survival were evaluated in field-cages on adelgid infested T. canadensis in southwestern Virginia. Adult S. coniferarum fed on both generations and all life stages of A. tsugae at rates comparable to other adelgid-specific predators, and survived for extended periods of time in the field. In objective two, host-range tests for S. coniferarum were conducted in a series of no-choice and paired-choice feeding, oviposition, and development studies. Scymnus coniferarum adults fed on all adelgid species, and completed development on HWA and Adelges piceae Ratz. Scymmnus coniferarum oviposition was extremely low. In the final objective, Douglas-fir, Pseudotusga menziesii Mirb., Shore pine, Pinus contorta Dougl., western white pine, Pinus monticola Dougl., and western hemlock, Tsuga heterophylla (Raf.) Sarg. host tree species were sampled in Tacoma, Washington to investigate the life history of S. coniferarum and associated adelgid prey species in the western United States. Scymnus coniferarum adults were found on both pine species, Douglas fir, and western hemlock, and seemed to move between host tree species seasonally. Each host tree supports a different adelgid species, and a limited diet of strictly HWA in host-range tests could have contributed to low oviposition rates. This study suggested that S. coniferarum is a voracious predator of HWA in the field and laboratory. However, S. coniferarum laid very few eggs in laboratory studies, and zero eggs were recovered in field-cage analyses. This suggested that S. coniferarum may rely on multiple adelgid species to reproduce and establish in the eastern United States.
- Biology and Host-Range Testing of Laricobius kangdingensis sp. n. (Coleoptera: Derodontidae), a Newly Discovered Predator of Hemlock Woolly Adelgid, Adelges tsugae Annand (Homoptera: Adelgidae)Gatton, Holly A. (Virginia Tech, 2005-04-25)The biology and host-specificity of Laricobius kangdingensis sp. n. (Coleoptera: Derodontidae), a new predator of hemlock woolly adelgid (HWA), Adelges tsugae Annand (Homoptera: Adelgidae) were investigated and compared with that of a related predator of HWA, L. nigrinus Fender. Adults became active in June 2003; the males emerged first and in greater numbers than the females. The sex ratio of female to male was 1: 1.1. Laricobius kangdingensis sp. n. has four larval instars. The total number of eggs laid between 7 July 2003 and 7 August 2004 was 1327. Mean lifetime fecundity per female was 196.4 ± 53.4 eggs and 97.9 eggs for the P1 (parental gen.) and F1 generations, respectively. In comparison, lifetime fecundity for F1 L. nigrinus was 100.8 ± 89.6 eggs. Developmental rates were studied in fall 2003 and spring 2004. Combined with data gathered previously at 12 and 15ºC in early 2003, the 6, 9, and 18ºC data were used to determine lower temperature development thresholds for the egg (2.8ºC), larval (1.6ºC), and pre-pupal (5.8ºC) stages. The egg and larval thresholds are lower than those observed for L. nigrinus. Laricobius kangdingensis sp. n. individuals completed development only at 12 and 15ºC; however, these adults did not emerge from aestivation after pupation. Laricobius kangdingensis sp. n. appears to be host-specific. In paired-choice feeding tests, adults consumed significantly more HWA than two other adelgid species [eastern spruce gall adelgid, Adelges abietis (L.), and pine bark adelgid, Pineus strobi (Hartig)], the pine needle scale, Chionaspis pinifoliae (Fitch), and the woolly alder aphid, Paraprociphilus tessellatus (Fitch). In paired-choice oviposition tests, females laid more eggs on HWA-infested eastern hemlock than on any other test prey. In no-choice host suitability experiments larvae fed on HWA; eastern spruce gall adelgid; the larch adelgid, A. laricis Vallot; the balsam woolly adelgid, A. piceae (Ratzeburg); pine bark adelgid; and pine needle scale, but not on woolly alder aphid or elongate hemlock scale, Fiorinia externa Ferris. Although no larvae completed development in any of the bioassays, 6 out of 15 larvae (40%) in the HWA treatment reached the pre-pupal stage. One larva out of 6 reached the pre-pupal stage on pine bark adelgid.
- Biology of Laricobius nigrinus Fender (Coleoptera: Derodontidae) and its potential as a biological control agent of the hemlock woolly adelgid, Adelges tsugae Annand (Homoptera: Adelgidae) in the eastern United StatesZilahi-Balogh, Gabriella M. G. (Virginia Tech, 2001-11-09)The biology of Laricobius nigrinus Fender (Coleoptera: Derodontidae) and its potential for control of hemlock woolly adelgid (HWA), Adelges tsugae Annand (Homoptera: Adelgidae) in the eastern United States were investigated. Laricobius nigrinus completed development on HWA in laboratory studies. There are four larval instars. Mean larval consumption was 225.9 and 252.3 HWA eggs at 12 and 18 °C, respectively. Post-aestivation activity period was 36.6 and 30.8 weeks for males and females at 13 °C, respectively. Mean lifetime fecundity was 100.8 eggs over a mean ovipositional period of 13.2 weeks. Laricobius nigrinus is host specific. In paired-choice and no-choice oviposition tests, L. nigrinus laid more eggs in HWA ovisacs than other test species. Laricobius nigrinus consumed more eggs of HWA than eggs of Adelges piceae (Ratzeburg) and Pineus strobi (Hartig) but not of Adelges abietis (L.). In larval development tests, L. nigrinus only completed development on HWA. A two-year field study conducted in British Columbia showed that: 1) the life cycle of HWA in British Columbia is similar to that previously reported in Virginia and Connecticut; 2) L. nigrinus adults undergo an aestival diapause that coincides with the diapause of the first instar HWA sistens. Adult activity beginning in autumn coincides with resumption of development of the sistens generation; 3) oviposition and subsequent larval development of L. nigrinus coincide with oviposition by HWA sistens adults. Temperature-dependent development was determined for egg, larval, pre-pupal and pupal stages of L. nigrinus at five constant temperatures (9, 12, 15, 18 and 21 °C). Development time was inversely proportional to temperature between 9 and 18 °C. Laricobius nigrinus did not complete development at 21 °C. Minimum developmental temperatures for eggs (6.5 °C), larvae (5.1 °C), pre-pupae (3.8 °C), and pupae (3.1 °C) were determined by extrapolation of linear regression equations to the x-intercept. Degree-days calculated for eggs, larvae, pre-pupae, pupae, and egg to adult were 54.6, 161.3, 196.1, 212.8, and 666.7, respectively. The laboratory derived degree-day model for predicting egg hatch was validated with field data collected in British Columbia. Observed median egg hatch at three of four sites over two years was within 15% of the predicted DD value (54.6).
- Cerceris fumipennis "The Smokey Winged Beetle Bandit"Wantuch, Holly Anne; Kuhar, Thomas P.; Salom, Scott M. (Virginia Cooperative Extension, 2015-09-24)Discusses the life cycle of Cerceris fumipennis a species of solitary digger wasp. The conspicuous manner by which this wasp provisions its nest makes it a quite useful biosurveillance tool for detecting the presence of Emerald Ash Borers Agrilus planipennis.
- Characteristics and Perceptions of Cost-share Funding for Emerald Ash Borer Mitigation in Virginia Urban AreasStewart, Peter William (Virginia Tech, 2019-06-19)Since most invasive forest pests first establish in urban areas, detection and containment of these pests within cities is important to the health of all forests. While the emerald ash borer (EAB) (Agrilus planipennis Fairmaire) has proved difficult to contain, efforts continue to mitigate the impacts of its spread. As part of those efforts, the Virginia Department of Forestry (VDOF) initiated its Emerald Ash Borer Treatment Program (EABTP) in 2018, providing financial incentives for insecticidal protection of ash trees. To better understand the role of incentives in promoting urban forest health, I conducted a study of properties, households, and practitioners involved in the program's first year. To examine where EABTP funding helped pay for tree protection, I conducted tree inventories on 16 urban participant properties. Concurrently with tree inventory work, I conducted web and mail surveys to examine homeowner engagement in preservation of threatened trees. Finally, to investigate the role of forest practitioners involved in program implementation, I conducted web surveys of VDOF foresters and Virginia arborists. Results demonstrated that on urban participant properties—typically large and wooded—white ash (Fraxinus americana) was the dominant species. Results from homeowner surveys demonstrated broad support for personal investment in tree preservation, and the significance of attitudinal predictors towards those intentions. Results from practitioner surveys demonstrated substantial, though not unanimous, support for the program as a benefit both to clients and forests. Implications of these findings are discussed in the context of future urban forest health initiatives.
- Competitive interactions among two specialist predators and a generalist predator of hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae)Flowers, Robbie Wayne (Virginia Tech, 2006-04-10)Competitive interactions among two specialist predators, Laricobius nigrinus Fender (Coleoptera: Derodontidae) and Sasajiscymnus tsugae Sasaji and McClure (Coleoptera: Coccinellidae), and a generalist predator, Harmonia axyridis 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 A. tsugae, 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 L. nigrinus and H. axyridis and reduced feeding by H. axyridis. 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 A. tsugae nymphs of the next generation relative to no-predator controls; however, L. nigrinus 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 H. axyridis. Conspecifics significantly altered the time allocated to specific behaviors for L. nigrinus and H. axyridis, 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 A. tsugae and implementing low-density releases to reduce the potential negative effects of intraspecific competition.
- Cost share payment and willingness to participate in Virginia's Pine Bark Beetle Prevention ProgramWatson, Adam (Virginia Tech, 2011-05-04)Forest management practices which reduce southern pine beetle (SPB) risk benefit not only the landowners who perform them, but all those who draw benefits from southern pine forests in Virginia, especially other forest owners within the same region. One such management practice is pre-commercial thinning (PCT), which is particularly unattractive to non-industrial private forest (NIPF) landowners because of the substantial costs and delayed financial returns involved. Since the benefits to society generated by PCT are not fully realized by the individuals who might implement it, there may be a market externality in which PCT is underprovided across the landscape. The Pine Bark Beetle Prevention Program (PBBPP) has the potential to correct this externality by reimbursing a portion of the costs of PCT for landowners who qualify. However, cost share incentives have been criticized for being ineffectual on the basis that landowners substitute publicly funded reimbursement for private investment, without altering their management practices. To investigate the effect of the PBBPP cost share for PCT, a survey was sent to 1,200 NIPF landowners in seven counties across the Piedmont and Coastal Plain physiographic regions of Virginia, where southern pine is prevalent and SPB hazard is a relevant concern. To measure willingness to participate in the program, a referendum style question was used in which the offered cost share ranged from 20% to 90%. Results of discrete choice models estimated from survey data indicate that cost sharing has a significant, positive effect on willingness to participate overall, though increasing reimbursement above 60% is unlikely to affect participation. Some landowners are not responsive or are less responsive to cost sharing due to personal and property characteristics.