Scholarly Works, Entomology

Permanent URI for this collection

https://hdl.handle.net/10919/24305
Research articles, presentations, and other scholarship

Browse

Browsing Scholarly Works, Entomology by Subject "07 Agricultural and Veterinary Sciences"

Now showing 1 - 2 of 2
  • Thumbnail Image
    The invasive tree, Ailanthus altissima, impacts understory nativity, not seedbank nativity
    Brooks, Rachel K.; Barney, Jacob; Salom, Scott M. (Elsevier, 2021-06-01)
    Ailanthus altissima, the invasive forest tree commonly known as the tree-of-heaven, has been associated with decreased levels of plant species richness and native species diversity. However, this relationship with resident plants has been inconsistently found and the tree's influence on the seedbank has yet to be studied. To further understand the long-term impact of this tree, ten paired invaded-uninvaded sites were identified in Virginia, USA in a variety of different-aged stands. The herbaceous and woody understories for each plot were inventoried and soil samples were collected and grown out for 34 weeks in a greenhouse. All plants were identified to the most detailed taxonomic level possible. In total, 35 woody understory species, 62 herbaceous understory taxa, and 77 seedbank taxa were identified. The relationship between A. altissima presence and i) the proportion of individual plants that are native, ii) the proportion of species that are native, iii) the native diversity, and iv) the nonnative diversity were analyzed. In addition, models including the invasion age were also considered. We show that A. altissima invasions were associated with a decrease in the proportion of native plants and species in the understory, but not in the seedbank. Nonnative woody diversity also increased with A. altissima presence. Additionally, the impact on the nativity of the woody understory became more extreme over time. We end by discussing the benefits of both managing A. altissima invasions early to limit its overall impact and including the management of other nonnative plants in A. altissima restoration plans.
  • Thumbnail Image
    Plant essential oils synergize various pyrethroid insecticides and antagonize malathion in Aedes aegypti
    Norris, Edmund J.; Gross, Aaron D.; Bartholomay, Lyric C.; Coats, J. R. (Wiley, 2019-12-01)
    Pyrethroid resistance is a significant threat to agricultural, urban and public health pest control activities. Because economic incentives for the production of novel active ingredients for the control of public health pests are lacking, this field is particularly affected by the potential failure of pyrethroid-based insecticides brought about by increasing pyrethroid resistance. As a result, innovative approaches are desperately needed to overcome insecticide resistance, particularly in mosquitoes that transmit deadly and debilitating pathogens. Numerous studies have demonstrated the potential of plant essential oils to enhance the efficacy of pyrethroids. The toxicity of pyrethroids combined with plant oils is significantly greater than the baseline toxicity of either oils or pyrethroids applied alone, which suggests there are synergistic interactions between components of these mixtures. The present study examined the potential of eight plant essential oils applied in one of two concentrations (1% and 5%) to enhance the toxicity of various pyrethroids (permethrin, natural pyrethrins, deltamethrin and β-cyfluthrin). The various plant essential oils enhanced the pyrethroids to differing degrees. The levels of enhancement provided by combinations of plant essential oils and pyrethroids in comparison with pyrethroids alone were calculated and synergistic outcomes characterized. Numerous plant essential oils significantly synergized a variety of pyrethroids; type I pyrethroids were synergized to a greater degree than type II pyrethroids. Eight plant essential oils significantly enhanced 24-h mortality rates provided by permethrin and six plant essential oils enhanced 24-h mortality rates obtained with natural pyrethrins. By contrast, only three plant essential plants significantly enhanced the toxicity of deltamethrin and β-cyfluthrin. Of the plant essential oils that enhanced the toxicity of these pyrethroids, some produced varying levels of synergism and antagonism. Geranium, patchouli and Texas cedarwood oils produced the highest levels of synergism, displaying co-toxicity factors of > 100 in some combinations. To assess the levels of enhancement and synergism of other classes of insecticide, malathion was also applied in combination with the plant oils. Significant antagonism was provided by a majority of the plant essential oils applied in combination with this insecticide, which suggests that plant essential oils may act to inhibit the oxidative activation processes within exposed adult mosquitoes.