Browsing by Author "Mayfield, Albert E."

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    Establishment of Laricobius nigrinus (Coleoptera: Derodontidae) in Virginia and assessment of its impact on hemlock woolly adelgid, Adelges tsugae (Hemiptera: Adelgidae), throughout the eastern U.S.
    Heminger, Ariel (Virginia Tech, 2017-01-18)
    Management of hemlock woolly adelgid (HWA), Adelges tsugae (Hemiptera: Adelgidae), is currently being implemented through several different methods including the release of host-specific predators such as Laricobius nigrinus Fender (Coleoptera: Derodontidae). Releases of this predator began in 2003. In 2014, an assessment of the efficacy of L. nigrinus at release sites from New Jersey to Georgia. Field sites were chosen based on the presence of moderate to high densities of HWA, that L. nigrinus was released at least four years prior to the start of the study, and that the predator was determined to be established at that site. Three treatments were set up at each of the sites: no cage, closed exclusion cage, and open cage. Three assessments were taken during key points throughout the season in order to monitor both HWA and L. nigrinus populations. Larval predator were recovered from most of the sites in year one and in higher numbers in year two. Many sites at which L. nigrinus were recovered showed high predation rates of HWA in uncaged samples ranging from 1.5 to 47.3% in year one and 0 to 66% in year 2. A survey for L. nigrinus establishment at previous release sites in VA was conducted. These sites date back as far as 2003 and as recently as 2015. Beat sheeting and branch clippings were conducted to recover Laricobius spp. adults and larvae, respectively. The recovered insects were then identified to species through genetic analysis. A mix of the introduced L. nigrinus and the native L. rubidus LeConte (Coleoptera: Derodontidae) were recovered at some sites, and only L. rubidus were recovered from others. Higher numbers of Laricobius were recovered in spring of year two. Overall, tree health in Virginia decreased from spring 2015 to 2016.
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    Impact of the introduced predator, Laricobius nigrinus, on ovisacs of the overwintering generation of hemlock woolly adelgid in the eastern United States
    Jubb, Carrie S.; Heminger, Ariel R.; Mayfield, Albert E.; Elkinton, Joseph S.; Wiggins, Gregory J.; Grant, Jerome F.; Lombardo, Jeffrey A.; McAvoy, Thomas J.; Crandall, Ryan S.; Salom, Scott M. (2020-04)
    Hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae), is an invasive pest causing significant mortality to eastern and Carolina hemlock in eastern North America. Since 2003, management of HWA has included targeted release of the HWA predator Laricobius nigrinus Fender (Coleoptera: Derodontidae), native to western North America. Establishment of L. nigrinus at release sites is well documented, but investigations of its impact on HWA populations have been limited. A four-year (2014-2018), two-phase study using predator exclusion cages to assess the impact of L. nigrinus on HWA was conducted at nine previous release sites in the eastern United States. Significantly more HWA sistens ovisacs were disturbed on no-cage and open-cage branches than on caged branches where predators were excluded. Mean disturbance levels on cage, no-cage and open-cage branches was 8, 38, and 27 percent, respectively. Seven of nine sites had a mean HWA ovisac disturbance greater than 50% for at least one year. Winter temperatures were also a significant factor in overall mortality of the sistens generation with a mean of 46% on study branches. Six of nine sites had a mean overall mortality (winter mortality and predation) greater than 80% for at least one year. Larvae of Laricobius spp. were recovered at all sites during this study. Sequencing of the COI gene from recoveries in Phase One (2015 and 2016) indicated that 88% were L. nigrinus and 12% were L. rubidus LeConte. Microsatellite analysis performed during Phase Two (2017 and 2018) indicated that approximately 97% of larval recoveries were L. nigrinus, 2% were hybrids of L. nigrinus and L. rubidus, and 1% were L. rubidus. Results of this study suggest that L. nigrinus can significantly impact the HWA sistens generation ovisacs and continued investment in the use of this species as a biological control is recommended.
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    Temperature-dependent Development, Survival, and Oviposition of Laricobius osakensis (Coleoptera: Derodontidae): A Specialist Predator of Adelges tsugae (Hemiptera: Adelgidae)
    Foley, Jeremiah R.; Mcavoy, Thomas J.; Saint-Amant, Remi; Regnière, Jacques; Biggs, Abby; Wright, Erika; Mayfield, Albert E.; Brewster, Carlyle; Salom, Scott M. (Oxford University Press, 2022-08-01)
    A predator, Laricobius osakensis Montgomery and Shiyake (Coleoptera: Derodontidae), is being mass-produced and released for the biological control of the invasive hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae). To better understand and predict the seasonality of this predator in North America, the development and reproduction of L. osakensis were evaluated at constant temperatures ranging from 5 to 22°C. The predicted seasonal biology was compared with data from field collections. L. osakensis did not complete development from egg to adult at the two lowest temperatures tested, 5 and 8°C, but did so at the highest temperature of 22°C. The minimum development thresholds were estimated for eggs (4.2°C), first (1.8°C), second (5.5°C), third (4.6°C), and fourth instar (4.1°C), prepupa (3.6°C), and pupa (7.5°C). Oviposition rates were significantly greater at 5 and 10°C than at 20 and 25°C. Head capsule width significantly increased for each of the four larval instars with a mean of 0.19, 0.26, 0.35, and 0.44 mm, respectively. Laboratory and field data were used to develop a phenology forecasting model to predict the occurrence of all developmental stages of L. osakensis. This model will allow land managers to more accurately predict the optimal timing for L. osakensis larval sampling throughout its established range.