The hemlock woolly adelgid (HWA) Adelges tsugae (Annand) (Hemiptera: Adelgidae), has spread throughout most of the range of eastern hemlocks, Tsuga canadensis (L.) and the entire range of Carolina hemlocks, Tsuga caroliniana (Engelman) in eastern North America. Forest managers often implement an integrated pest management (IPM) strategy that combines chemical, silvicultural, and biological control tactics to create a more sustainable and effective approach for managing HWA. Laricobius spp. (Coleoptera: Derodontidae) are the primary biological control agents within IPM scenarios for HWA. Imidacloprid (IMI), the most widely used insecticide for HWA management, is typically applied to the soil below HWA infested trees and breaks down into several metabolites, including two with insecticidal properties; 5-hydroxy imidacloprid (5H-IMI) and imidacloprid-olefin (IMI-OLE). Imidacloprid-olefin is known to be up to 14 times as lethal to HWA as IMI and is produced as imidacloprid is first hydroxylated into 5H-IMI and further metabolized into IMI-OLE. Because Laricobius spp. spends half of its life in aestival diapause in soil below HWA infested trees, there is the potential for these biological control agents to encounter toxic residues within an IPM setting. Imidacloprid and its metabolites are known to cause mortality in Laricobius spp. feeding on HWA from previously treated trees, but the impact of soil applied imidacloprid on their subterranean survivorship has not been studied. Furthermore, there is limited knowledge on the subterranean portion of Laricobius spp. life cycle. The first study determined the depth to which Laricobius spp. burrowed during their subterranean life phase using 3D X-ray microscopy. When held in containers with two differing soil compaction intensities, 0.2 kg/cm2 and 0.5 kg/cm2, Laricobius spp. were found to burrow an average (± SE) of 2.7 ± 1.5 cm and 1.4 ± 1.3 cm deep, respectively. The second study assessed the effect of three different imidacloprid soil treatments; soil injection, soil drench and CoreTect tablets, on the subterranean survivorshiop of Laricobius spp. The soil drench application technique applied in fall 2020 consistently resulted in significantly higher IMI, 5H-IMI, and IMI-OLE residues than the other two treatments over both years of this study (2021 and 2022). The soil injection treatments from both 2020 and 2017 resulted in above average field emergence of beetles in 2021 and 2022, with relatively insignificant residue quantities present. This study suggests that the soil injection treatment method provides a lower level risk of metabolite exposure to Laricobius spp. compared to soil drench and CoreTect tablet imidacloprid application methods. / Master of Science in Life Sciences / In eastern North America, there are two species of hemlock trees whose longevity and unique shade tolerant adaptations are important to the ecosystems within which they are found. Eastern hemlocks range from southeastern Canada to the southern Appalachian Mountains, while Carolina hemlocks are restricted to the southern Appalachians from northern Georgia to Virginia. Since its first formal identification in Richmond, VA in 1951, the hemlock woolly adelgid (HWA) has caused widespread damage and mortality throughout much of the range of eastern hemlocks and the entire range of Carolina hemlocks. HWA consumes nutrients and restricts water flow within the tree, eventually leading to tree mortality. Forest managers typically rely on an integrated approach, that combines chemical applications with the simultaneous release of insects that naturally attack HWA on untreated trees within the same forest setting. Imidacloprid is the most widely used insecticide for HWA management and is typically applied to the soil below HWA infested trees. This insecticide is absorbed through the roots and travels through the tree where HWA feed and die as a result. Laricobius spp., the primary insect consuming HWA on infested trees, spends part of their life in a below ground summer dormancy. Imidacloprid and its secondary compounds are known to cause mortality in Laricobius spp. feeding on HWA from treated trees, but the impact of soil applied imidacloprid on their below ground survivorship has not been studied to date. Furthermore, while extensive studies have taken place to understand the biology of Laricobius spp., there is limited knowledge about their dormant state. In one study, the depth to which Laricobius spp. burrowed during their below ground life phase was determined using 3D X-ray microscopy. In a second study, the effect of three common imidacloprid treatments; soil injection, soil drench, and CoreTect tablets, on below ground survivorship was examined. Laricobius spp. were found to burrow an average (± S.E.) of 2.7 ± 1.5 cm and 1.4 ± 1.3 cm deep in soil compacted at 0.2 kg/cm2 and 0.5 kg/cm2, respectively. Chemical residue quantities were greatest in soil treated with soil drench in fall 2020, and were found to significantly impact Laricobius spp. survival. Overall, survival was the lowest from the soil treated with CoreTect tablets in 2020. Surival was the greatest from soil that received soil injection treatments in both 2020 and 2017 and had relatively insignificant imidacloprid residues present where the insects typically occur in the soil. Findings from this study suggest that imidacloprid application using the soil injection method is a less risky technique for chemical control in an IPM setting when compared to soil drench and CoreTect methods.

The hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae) is a small, non-native insect that feeds on hemlock (Tsuga spp.) species native to the eastern United States. One biological control agent, Laricobius osakensis, shows promise due to its voracious feeding on and synchronous life cycle with HWA. This beetle species is originally from Japan and has undergone all the necessary testing while in quarantine, gaining permission for field release in 2010. Field releases began in the fall of 2012 and continued the following fall. Reproduction occurred at the first year's field sites with beetles recovered at both sites the following fall. During the second year of field work, beetle recovery was low due to winter temperatures that caused high HWA mortality. All of the L. osakensis beetles released in the field are first reared in an Insectary on Virginia Tech's campus. To improve health of these beetles during rearing, a series of chemical amendments were added to the water baths where HWA infested cut hemlock branches were placed. HWA samples were taken from each treatment and analyzed for carbon, nitrogen and total carbohydrates and beetles emergence was recorded in relation to prescribed treatment. None of the treatments appeared as the best for improving HWA health, but there were differences between the sampling months within the two years. These differences in month correlate with the biological processes occurring within HWA at these times such as reproduction and preparation for aestivation. No treatment helped increase beetle emergence. / Master of Science in Life Sciences

Dissertation (PhD)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The basic biology of Eriosoma lanigerum (Hausmann) and its natural enemy, Aphelinus mali (Haldeman), was investigated in the Western Cape Province of South Africa. The first instar nymph can be identified by the absence of cornicles and the adult female by the presence of the vulva. Body length and distance between cornicles can be used to distinguish between the 2nd , 3rd and 4th instars. The development of E. lanigerum was negatively influenced by temperatures above 27DC. The net replacement rate (Ro) and intrinsic rate of increase (rm) peaked at 20DC. The theoretical lower and upper threshold temperatures for development were estimated at 4.48DC and 28.07DC, respectively. Crawlers of E. lanigerum migrated from the roots up into the trees during spnng to start new infestations. Colonies became visible from December and maximum colony numbers were reached from the end of summer until autumn, at which time most of the colonies were parasitised by A. mali. Colony numbers declined at the end of autumn after high parasitism and the appearance of winged E. lanigerum. The aphid overwintered on the tree. Chemical sprays, rain during spring and high temperature influenced population numbers negatively. E. lanigerum can be monitored by counting the unparasitised colonies in leaf axils of half of each of 25 trees per 2 hectare plot with 5 unparasitised colonies as the economic threshold. Sampling error was high at 40% but increasing the number of trees did not reduce it. Presence-absence sampling, which will reduce the time required for monitoring, did not seriously compromise the reliability of decisions regarding the necessity for intervention. Chemicals containing nitrogen usually sprayed for bitterpit control stimulated the settling of E. lanigerum crawlers on Granny Smith trees, while fruit weevil barriers for the control of Phlyctinus callos us Boh. limited crawler movement into the trees but did not prevent colonisation. All the postembryonic developmental stages of E. lanigerum were parasitised by A. mali. Complete parasitism of the population was never reached as younger instars sheltered under other aphids and mummified aphids. Development of A. mali was not influenced negatively by high temperatures. The minimum developmental temperature and number of degree days needed for development of the larval stage and emergence of the adult from the mummy were .6.72°C and 172.41°D, and 10.27°C and 109.89°D respectively. Mummies collected during early winter survived long periods of cold storage in postdiapause. The rrummum threshold temperature for postdiapause development of A. mali was ·10.15°C. Most chemicals tested against A. mali adults were highly toxic to the wasp, except endosulfan and two growth regulators, flufenoxuron and fenoxycarb. The mortality of adults exposed to the fungicides tested was low within the first 24 hours. The percentage emergence from the mummies was high for all chemicals tested, but more than 60% of the adults died soon after emergence from mummies treated with chlorpyrifos. Nearly 30% of the adults died soon after they emerged from carbaryl (XLR-Plus) and fenthion treated mummies. The growth regulators, flufenoxuron and fenoxycarb, did not influence fecundity adversely. / AFRIKAANSE OPSOMMING: Die basiese biologie van Enosoma lanigerum (Hausmann) en sy natuurlike vyand, Aphelinus mali (Haldeman), in die Weskaap Provinsie van Suid-Afrika isondersoek. Die eerste instar nimf kan aan die afwesigheid van kornikels en die volwassenes aan die teenwoordigheid van die vulva uitgeken word. Die liggaamslengte en afstand tussen die kornikels kan gebruik word om tussen instar 2, 3 en 4 te onderskei. Die ontwikkeling van E. lanigerum word nadelig deur temperature bo 27°C beïnvloed. Die netto vervangingstempo (Ro) en intrinsieke tempo van toename (rm) was die hoogste by 20°C. Die teoretiese minimum en maksimum temperatuur drempelwaardes vir ontwikkeling was 4.48°C en 28.07°C onderskeidelik. In die lente beweeg E. lanigerum kruipers op vanaf die wortels tot in die bome om nuwe kolonies te begin. Kolonies is sigbaar vanaf Desember en die hoogste koloniegetalle word aan die einde van die somer tot die herfs bereik, wanneer die meeste van die kolonies dan ook deur A. mali geparasiteer word. Teen laat-herfs neem koloniegetalle af as gevolg van hoë parasitisme en die verskyning van gevleuelde E. ,lanigerum. E. lanigerum oorwinter op die appelboom. Chemiese behandelings, reën gedurende die lente en hoë temperatuur beïnvloed koloniegetalle nadelig. E. lanigerum kan deur die aantal ongeparasiteerde kolonies in die blaaroksels van die helfte van 25 bome per 2 hektaar blok te tel, met 5 ongeparasiteerde kolonies as die ekonomiese drempelwaarde, gemonitor word. Die steekproefnemingsfout was hoog (40%), maar kon nie verminder word deur die aantal bome wat gemonitor is te verhoog nie. Steekproefneming, vir aan- of afwesigheid van kolonies, wat monitortyd sal verminder, het min invloed op die betroubaarheid van besluitnemings oor die noodsaaklikheid van bespuitings gehad. Stikstofbevattende chemikalieë, wat vir die beheer van bitterpit gespuit word, stimuleer vestiging van E. lanigerum kruipers op Granny Smith bome, terwyl snuitkewerversperrings, vir die beheer van Phlyctinus callosus Boh., die opwaartse beweging van kruipers in die bome beperk, maar nie kolonievorming van E. lanigerum verhoed nie. Alle postembrioniese ontwikkelingstadiums van E. lanigerum is deur A. mali geparasiteer. Totale parasitisme is nooit bereik nie, omdat jonger instars onder ander bloedluise en gemummifiseerde bloedluise skuil. Die ontwikkeling van A. mali word nie deur hoë temperature benadeel nie. Die minimum ontwikkelingstemperatuur en graaddae, nodig vir ontwikkeling van die larwale stadium en die verskyning van die volwassene uit die mummie, was 6.72°C met 172.4loD en 10.27°C met 109.89°D, onderskeidelik. Mummies wat vroeg in die winter versamel is, het lang periodes van koelopberging oorleef. Die minimum temperatuur drempelwaarde vir A. mali ontwikkeling in postdiapouse was 10.15°C. Die meeste van die chemikalieë wat getoets is, was hoogs toksies vir die volwasse wesp, behalwe endosulfan en die twee groeireguleerders, flufenoxuron en fenoxycarb. Die mortaliteit van volwassenes wat aan swamdoders blootgestel is, was laag binne die eerste 24 uur na blootstelling. Die persentasie uitkoms vanuit mummies was hoog vir al die chemikalieë wat getoets is, maar met chlorpyrifos het 60% van die volwassenes net na uitkoms doodgegaan. Ongeveer 30% van die volwassenes is dood na verskyning vanuit mummies wat met carbaryl (XLR-Plus) en fenthion gespuit is. Die groeireguleerders, flufenoxuron en fenoxycarb, het nie die vrugbaarheid van die parasiet merkbaar beïnvloed nie.

Dissertation (PhD (Agric))--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: A study was made of the basic biology of subterranean Eriosoma lanigerum (Hausmann) populations in apple orchards in the Western Cape Province of South Africa. The absence of cornicles and the presence of a vulva could be used to identify 1st instar nymphs and adults respectively. Body length, body width and length of the hind femur are useful for separating 2nd , 3rd and 4th instars. However, separation of 2nd from 3rd instar nymphs was very unreliable. Maximum population growth rate was at 23°C while at 30 °C population growth was zero. The estimated minimum and maximum threshold temperatures for development were 4.32 and more than 30°C respectively. Numbers of underground E. lanigerum in soil samples taken using mechanical and hand augers were similar. However, numbers of aphids in samples were influenced by the distance from the trunk at which the samples were taken and the presence and the type of root material in the samples. More aphids were recorded close to the trunk, and at a given distance from the trunk more aphids were recorded if there was root material in the sample, especially if the roots were galled. early autumn (February, March) and declined during winter, especially if the winter rainfall was high. These cycles coincided with the nitrogen cycles in the roots. Embryos were also present in all instars throughout the year. There were more embryos in the 4th instar and adult aphids than in the other instars. The highest number of embryos in the 4th instar and adult aphids occurred during spring, which coincided with peak nitrogen levels in the roots of apple trees. Nitrogen levels in root material adjacent to galls and in ungalled roots were higher than in root galls. A number of entomopathogenic fungi, including species of Conidiobolus, Hirsufella and Beauveria were found. Their present contribution to biological control is not known. A straw mulch suppressed subterranean E. lanigerum population levels at least as well as the soil insecticide, imidacloprid, currently in use. / AFRIKAANSE OPSOMMING: 'n Studie van die basiese biologie van ondergrondse bevolkings van , Eriosoma lanigerum (Hausmann) is in appelboorde in die Weskaap Provinsie van Suid-Afrika uitgevoer. Die afwesigheid van kornikels en die aanwesigheid van 'n vulva kon gebruik word om die 1ste instar nimfe en volwassennes onderskeidelik te identifiseer. Liggaamslengte, liggaamsbreedte en die lengte van die agterste femur kon gebruik word om die 2de , 3de en 4de instars van mekaar te onderskei. Onderskeiding tussen 2de en 3de instar nimfe was egter baie onbetroubaar. Maksimum bevolkingsgroei het by 23°C plaasgevind, terwyl dit nul was by 30 °C. Die beraamde minimum en maksimum temperature vir ontwikkeling was by 4.32 en meer as 30°C onderskeidelik. Getalle van ondergrondse E. lanigerum in grondmonsters wat geneem is met gebruik van meganiese en hand bore was eenders. Getalle plantluise in monsters is egter beïnvloed deur die afstand vanaf die stam waarby die monsters geneem is en die teenwoordigheid van wortelmateriaal in die monsters. Meer plantluise is aangeteken as daar wortelmateriaal in die monsters was, en veral as daar galle op die wortels was. Die appelbloedluis was dwarsdeur die jaar ondergronds aktief. Bevolkingsvlakke het gedurende die vroeë somer (November, Desember) en vroeë herfs (Februarie, Maart) toegeneem, en gedurende die winter afgeneem, veral as die winterreënval hoogwas. Embrio's was ook teenwoordig dwarsdeur die jaar. Daar was meer embrio's in die 4de instar en volwasse plantluise as in die ander instars. Die hoogste aantal embrio's in die 4de instar en volwasse plantluise het in die lente voorgekom, wat saamgeval het met piek stikstofvlakke in die wortels van appelbome. Stikstofvlakke in wortelmateriaal aangrensend aan wortels en in wortels sonder galle was hoër as in wortelgalle. Talle entomopatogeniese swamme, insluitend spesies van Conidiobolus, Hirsufella en Beauvaria IS gevind. Hulle huidige bydrae tot biologiese beheer is nie bekend nie. 'n Strooideklaag het ondergrondse bevolkingsvlakke van E. lanigerum tot ten minste dieselfde mate as die grondinsektedoder, imidacloprid, wat tans in gebruik is, onderdruk.

Thesis (Ph. D.) -- University of Western Sydney, Hawkesbury, 2000. / Includes bibliographical references (leaves 160-187).

Thesis (M.S.)--University of Tennessee, Knoxville, 2008. / Title from title page screen (viewed on Mar. 13, 2009). Thesis advisor: Jerome F. Grant. Vita. Includes bibliographical references.

Thesis (M.S.)--University of Tennessee, Knoxville, 2007. / Title from title page screen (viewed on June 4, 2008). Thesis advisor: Paris L. Lambdin. Vita. Includes bibliographical references.

No description available.

Masters of Science / Genetic analysis for resistance to Woolly Apple Aphid in apple rootstock breeding populations MC Selala MSc Thesis, Department of Biotechnology, Faculty of Science, University of the WesternCape. The Woolly Apple Aphid (WAA) Eriosoma lanigerum (Hausm.) (Homoptera: Aphididae) is economically one of the most important pests in apple commercial production in the Western Cape province, South Africa. The apple cultivar Northern Spy possesses a single major gene (Er1) responsible for E. lanigerum resistance. This cultivar has been used as a commercial rootstock in apple breeding programmes. There are other genes also implicated in resistance to E. lanigerum from other cultivars. Manipulation and pyramiding of the E. lanigerum resistance genes (Er1, Er2 and Er3) might provide a necessary control for commercial apple production. The aim of this study was to construct a genetic linkage map for apple using microsatellite markers. The use of marker-assisted selection would greatly benefit local apple breeding programmes. Ninety six seedlings from a Northern Spy × Cox Orange Pippin mapping population were used for genetic linkage construction. Phenotypic data collection and analysis were performed to determine the E. lanigerum infestation patterns and the levels of resistance conferred by the Er1 gene from Northern Spy using 52 in vitro propagated seedlings in the greenhouse. Classification and quantification analysis showed association patterns between first assessments (30 days) to second assessment (60 days) in all replicate blocks. Roots and shoots data showed that it could be useful in quantitative trait loci (QTL) analysis, but may be used in different QTLs beingidentified due to the variations between roots and shoots data. A preliminary linkage map was constructed using a mapping population from Northern Spy × Cox Orange Pippin (96 seedlings).Fluorescently labelled published and predicted microsatellite markers were used in map construction. Primers were optimised using single apple cultivar and the detection of polymorphisms using nine apple cultivars. Optimised markers were multiplexed for high throughput data generation using the Polymerase Chain Reaction (PCR) technique. Multiplexed PCR products were pooled and analysed on an ABI 310 PRISM™ Genetic Analyser to determine allele fragment sizes, and the inherited segregation types in the seedlings. Computer software GenoTyper® 2.5.2 and JoinMap® 3.0 was used in data analysis from ABI 310 PRISM™Genetic Analyser and linkage map construction. Seventy two markers were used in linkage map construction, which produced nine linkage groups with some segments from the same linkage group. Twenty-one markers were aligned on the map 20 published and one predicted. Only one linkage group consisted of five markers while other linkage groups had two markers each. This study has proved that th preliminary linkage map could be used as the basis of a complete linkage map of Northern Spy × Cox Orange Pippin.

Eastern hemlock (Tsuga canadensis [L.] Carr.) is a foundation species that occupies a unique niche in forest ecosystems and which often forms pure stands throughout the eastern United States. Throughout the last half of a century, widespread mortality of T. canadensis had been occurring with the introduction of the invasive pest, hemlock woolly adelgid (Adelges tsugae Annand) (HWA). HWA now threatens to destroy millions of hectares of hemlock dominated forests and to disrupt its associated ecosystems. In order to determine how HWA impacts hemlock physiology, three sites with various degrees of infestation were chosen and half of the trees at each site were treated with imidacloprid (Merit® 2 F, Bayer, Kansas City, MO) while the rest were left untreated. Needle gas exchange was assessed monthly using a LI-COR 6400 portable open path gas exchange system (LI-COR Inc, Lincoln NE). Chlorophyll fluorescence and bud break were also characterized for all trees at two of the three sites. After one complete growing season, we found a slight increase in photosynthetic rates (4.98 %), increased bud break at Fishburn (562 %) and Mountain Lake (25.6 %) sites, and no change in chlorophyll fluorescence for imidacloprid treated trees. These results suggest that HWA is causing tree mortality largely through a reduction of leaf area and not a reduction in leaf level photosynthetic capacity. By quantifying the physiological response of T. canadensis to HWA, better insights can be made into understanding tree decline as it relates to HWA. / Master of Science