The spotted lanternfly, Lycorma delicatula (White) (Hemiptera: Fulgoridae), is a new invasive insect from Asia that is currently spreading in the Mid-Atlantic region of the US, where it has become a pest of economic concern for many industries in their invaded range. The purpose of this research was to document L. delicatula phenology in Virginia, their feeding impact to trees, and to test a rearing protocol in quarantine laboratory conditions. First, using field plots and weekly observational surveys, L. delicatula phenology was documented in 2019 and 2020 in Winchester, Virginia. I showed that L. delicatula were active from late April into November for each sampling year, and that the timing of life stage events varied only slightly between years. I also calculated cumulative average growing degree days for each life stage event using a lower developmental threshold of 10°C. Additionally, I confirmed that the host range of L. delicatula narrows as they progress through development. These results will help growers and land managers develop integrated pest management plans targeting L. delicatula. Second, dendrochronological methods were used to quantify L. delicatula feeding injury to Ailanthus altissima (Miller) Swingle (Sapindales: Simaroubaceae), Juglans nigra L. (Fagales: Juglandaceae), and Liriodendron tulipifera L. (Magnoliales: Magnoliaceae). Two sites in Pennsylvania that have experienced high populations and heavy feeding pressure from L. delicatula since 2016 were used to collect tree cores for analysis. I found evidence suggesting L. delicatula is capable of reducing the growth of A. altissima, but did not find the same evidence in the wood of the other tree species tested. Additionally, I found evidence that systemic insecticide treatments may reduce or prevent damage to A. altissima fed on by L. delicatula. Additional dendrochronological studies on the damage inflicted by L. delicatula feeding could shed light on the long-term impact of this new invasive tree pest. Lastly, a protocol for rearing L. delicatula was tested inside Virginia Tech's Insect Quarantine Laboratory. Three different cuttings of A. altissima (apical meristems, epicormic shoots, and field collected foliage) were tested to determine the best food source for L. delicatula in quarantine laboratory conditions. Overall, I did not find a significant difference between food treatments, however a greater proportion of third instars developed into fourth instars in the apical meristem treatment. I suggest future L. delicatula rearing research include the use of potted plants and/or multiple species. Though I had low success in rearing adult L. delicatula to produce egg masses, this method may prove useful for rearing early instars from eggs or sustaining field collected specimens for short durations. Research expanding our knowledge of L. delicatula will help us reach our goal of more effectively managing this pest species in the future. / Master of Science in Life Sciences / The spotted lanternfly, Lycorma delicatula (White), is a new invasive pest species impacting the eastern and northeastern regions of the United States. This insect uses its straw-like mouth parts to feed on the sap of many different plants including fruit trees, grapes, and several important ornamental and timber trees. Though they do not bite or sting, feeding can result in wilting, the growth of sooty mold, and sometimes plant mortality, making them an economic and nuisance pest in their invaded range. This research primarily focused on studying the timing of the spotted lanternfly's life cycle, feeding impact to trees, and a method for raising them in the laboratory for research purposes. The life-cycle of the spotted lanternfly was documented over two growing seasons in Winchester, VA and the timing of each life stage was shown to be similar between years. Additionally, it was confirmed that the spotted lanternfly feeds on fewer host species as it develops into an adult. Tree-ring analysis was used to identify spotted lanternfly feeding injury to tree-of-heaven, black walnut, and tulip poplar. I found evidence suggesting spotted lanternfly feeding can cause reduced growth in tree-of-heaven, but did not find similar evidence in the other species tested. A laboratory colony of spotted lanternflies would prove beneficial for additional research on this insect. I tested three different types of branches cut from the tree-of-heaven to identify the best food source for spotted lanternfly in laboratory conditions. The findings of this research will help develop pest management strategies to reduce the impact of this new pest in the US.

Brown marmorated stink bug (BMSB), Halyomorpha halys (Stål), has become an important pest of soybean in the Mid-Atlantic US. To assess the influence of tree borders on BMSB infestations in soybean, twelve fields were sampled weekly using five 3-min visual counts of BMSB on tree of heaven (TOH) (Ailanthus altissima) and other host trees along a wooded border, on the adjacent soybean edge, 15 m and 30 m into the soybean field. At all locations, BMSB densities increased on TOH wooded borders in July, then, gradually moved into adjacent soybean borders later in the summer. BMSB did not move far from the field edge, with approximately half as many bugs being present at 15 m into the field and very few being detected 30 m into the field. These results validate the use of border sprays for BMSB control in soybean. Additional studies conducted in 2013 and 2014 compared a visual plant inspection method with a standard sweep net strategy for sampling BMSB. Overall, the two methods were highly correlated with a correlation coefficient of R=0.83. Visual inspection appears to be an effective method for assessing BMSB populations in soybean. One of the major factors affecting the distribution and establishment of invasive species is climate. The CLIMEX modeling software uses climatic and biological factors of species to predict the geographic risk for pest outbreaks. A climate simulation model was run with CLIMEX to determine the potential distribution of BMSB in Virginia based on temperature. To develop a more accurate model, factors like resource availability and source population would need to be considered. / Master of Science in Life Sciences

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. / Doctor of Philosophy / Commonly called the tree-of-heaven, the nonnative invasive forest-tree Ailanthus altissima, is extensive, damaging, and spreading throughout North America. After finding large areas of declining tree-of-heaven being killed by two different fungal species (Verticillium nonalfalfae and V. dahliae), research has been focused on how to use these fungi to help us manage the tree-of-heaven. In Virginia, V. nonalfalfae has been confirmed killing large numbers of tree-of-heaven, while V. dahliae is suspected to be present in areas with lower levels of decline. The purpose of our research was to gain a better understanding of how these pathogens impact tree-of-heaven and their potential as biological control agents in Virginia. We first confirmed that V. dahliae is present in Virginia and can cause disease on tree-of-heaven. We then inoculated tree-of-heaven stands throughout the state to confirm that V. nonalfalfae effectively kills and spreads to adjacent tree-of-heaven regardless of V. dahliae presence or other climate or site variables. In contrast, we found that V. dahliae only causes low levels of disease and does not spread effectively. Next, we surveyed all known naturally infected V. nonalfalfae sites in Virginia and demonstrated that V. nonalfalfae persists long term within these stands, considerably reducing but not eradicating the tree-of-heaven, and that V. nonalfalfae's local prevalence may be higher than initially suspected. However, when tree-of-heaven seedlings were planted into soil collected from these infested sites, no disease developed, suggesting that V. nonalfalfae's survival within the soil may be limited. Lastly, by looking at tree-of-heaven stands, we found that the tree-of-heaven's presence is associated with a lower percentage of native plants and species in the understory, but not in the seeds present in the soil. In addition, we found that this impact on the woody plants in the understory appears to become more severe over time, supporting managing the tree-of-heaven as soon as possible. We conclude that V. nonalfalfae used as a biological control has a good potential of successfully limiting the tree-of-heaven in Virginia and support its registration as a biopesticide.

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Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) is a polyphagous, invasive, and highly significant pest of mid-Atlantic fruit orchards. Its capacity to invade orchards season-long is believed to be facilitated by the availability of wild host plants near orchards and the high dispersal capacity of adults and nymphs. Interactions between H. halys and its hosts were investigated via laboratory and field experiments. Rearing H. halys nymphs in the laboratory on several of its known wild and tree fruit hosts used alone and in combination showed that peach was much more suitable for nymphal development and survival than was apple, tree of heaven, or catalpa and that nymphal performance was enhanced on mixed host diets. Nymphs reared on different host plant diets yielded adults that differed in protein, sugar or lipid content, offering new insights into plant diet effects on H. halys nutrition. The majority of tree species identified from unmanaged woodlands next to apple orchards in Virginia and West Virginia were known hosts of H. halys. Passive trunk traps were developed to capture H. halys nymphs walking up and down tree trunks and used to measure their temporal patterns of movement onto and off of wild and tree fruit hosts at the orchard-woodland interface via weekly assessments during two consecutive seasons. More upward- than downward-walking nymphs were captured, which may be partially explained by the positively phototactic and negatively geotactic behavior of H. halys nymphs demonstrated in laboratory studies. Most nymphs captured while walking up and down trunks were second instars, although the data also reflected temporal changes in the distribution of instars and temporal variation in the numbers of nymphs captured. A field study to characterize injuries to apple and peach fruit at harvest from feeding by young or older nymphs early or late in the season revealed that feeding by young nymphs early in the season resulted in least injury to both crops. In combination, these studies greatly improve our understanding of the biology and ecology of H. halys in eastern fruit orchards and provide relevant data that will inform the development of ecologically-based management programs for it. / Ph. D.

No description available.