The impact of imidacloprid on the subterranean survivorship of Laricobius (Coleoptera: Derodontidae), a biological control agent of Adelges tsugae (Hemiptera: Adelgidae)
| Authors: | Ashleigh P. Hillen, Jeremiah R. Foley, Aaron D. Gross, Albert E. Mayfield, Jacob Williams, Kang Xia, Scott M. Salom |
| Year: | 2024 |
| Type: | Scientific Journal |
| Station: | Southern Research Station |
| DOI: | https://doi.org/10.1111/afe.12647 |
| Source: | Agricultural and Forest Entomology |
Abstract
1.The invasive hemlock woolly adelgid (HWA), Adelges tsugae (Annand) (Hemiptera: Adelgidae), has spread throughout most of the range of eastern hemlock, Tsuga canan-densis (L.), and the entire range of Carolina hemlock, Tsuga caroliniana (Engelman), in the United States.
2. Integrated pest management (IPM) of HWA combines chemical applications with the release of biological control agents on untreated trees within the same stand. Laricobius spp., Rosenhauer (Coleoptera: Derodontidae), have been used as biological control agents of HWA since 2003 and have subterranean and arboreal life phases that are syn-chronous with HWA's lifecycle. When utilizing IPM tactics, there is potential for Larico-bius spp. to settle below an insecticide‐treated tree for its subterranean phase.
3. Field investigations assessed the impact of historical (five years post treatment in 2017) and recent imidacloprid soil treatments (via soil injection, soil drench, and tablet in November 2020) on the subterranean survivorship of Laricobius spp. by quantifying con-centrations of imidacloprid and its metabolites to determine its potential impact on per-cent adult emergence from the soil.
4. We observed a significant treatment effect on mean soil concentration among applica-tion methods at the recent treatment site, but not the historical treatment site. Addition-ally, at the more recently treated site, significantly lower mean percent emergence was observed from soil drench and tablet imidacloprid applications after one year (2021), but by the following year (2022), that effect was no longer present.
5. This study supports recent recommendations to delay releases of Laricobius spp. for one‐year post‐treatment with imidacloprid. Furthermore, these data suggest when applying imidacloprid to a stand established with Laricobius spp., soil injection techniques pose the least risk to their subterranean survivorship.