Emerald Ash Borer (Coleoptera: Buprestidae) Densities Over a 6-yr Period on Untreated Trees and Trees Treated With Systemic Insecticides at 1-, 2-, and 3-yr Intervals in a Central Michigan Forest

Persistence and recovery of dinotefuran in eastern hemlock (Tsuga canadensis) foliage and twigs by UPLC-MS/MS and ELISA

BACKGROUND

Dinotefuran, a systemic neonicotinoid insecticide, is approved for control of hemlock woolly adelgid (HWA) (Adelges tsugae Annand), an invasive sap-feeding insect that can kill eastern hemlocks (Tsuga canadensis). Dinotefuran is highly water soluble, facilitating more rapid translocation and HWA control than other neonicotinoids, but its persistence is not well-known. Samples of needles and twigs were collected in spring 2021 from 50 hemlocks treated with a dinotefuran basal trunk spray in 2018 or 2019 (131-145 weeks and 85-93 weeks before sampling, respectively). Processed samples were analyzed with ultra-performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) and enzyme-linked immunosorbent assays (ELISA).

RESULTS

Dinotefuran residues were 4.6-6.1 times higher in needles than in twigs collected from the same trees. Average (±SE) residues in foliage samples collected from trees treated in 2019 ranged from 0.663 ± 0.243 to 0.564 ± 0.119 mg kg-1 , compared with 0.213 ± 0.033 and 0.225 ± 0.132 mg kg-1 in foliage from trees treated in 2018. Foliage residues from UPLC-MS/MS were consistently lower but strongly related to those from ELISA. Matrix effects appeared to disrupt ELISA analysis of twigs. None of the 25 trees treated in 2019 had live HWA when samples were collected in 2021 while low densities of HWA were observed on 52% of trees treated in 2018.

CONCLUSIONS

Dinotefuran was recovered from hemlock foliage, and to a lesser extent twigs, >2 years post-treatment. This, along with its relatively rapid translocation, suggests dinotefuran is a viable option for protecting declining or heavily infested hemlocks from HWA. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of emamectin benzoate trunk injections on protection of neighboring ash trees against emerald ash borer (Coleoptera: Buprestidae) and on established biological control agents

The emerald ash borer (EAB), Agrilus planipennis Fairmaire, is the most destructive invasive pest on ash (Fraxinus spp.) in the United States. We determined whether ash trees injected with emamectin benzoate (EB) could protect untreated neighboring ash trees. We also determined whether the selective treatment of ash trees with EB injections had adverse effects on the establishment of introduced larval parasitoids Tetrastichus planipennis Yang and Spathius galinae Belokobylskij & Strazenac. In experiment one, trees were treated with EB and then retreated 3 years later. Five years post initial treatment, we found that 90% of treated ash trees retained healthy crowns, significantly higher than those of untreated control ash trees (16%). For experiment two, trees only received one treatment of EB and after 2 years 100% of treated ash trees retained healthy crowns, significantly higher than those of untreated ash trees (50%). In both experiments, we found that distance from the central EB-treated tree was not a significant predictor for tree health or presence of EAB exit holes. Although distance from the EB-treated trees appeared to have a significant positive relationship with woodpecker feeding signs on neighboring trees, such relationships did not result in significant differences in the proportion of neighboring ash trees retaining healthy crowns between EB treatment and control plots. The introduced EAB parasitoids appeared to have established equally well between treatment and control plots. Findings are discussed in the context of integration of EB trunk injection with biological control for protection of North American ash against EAB.

Persistence and distribution of dinotefuran in tree of heaven

Spotted lanternfly (SLF) (Lycorma delicatula (White)), an invasive planthopper discovered in Pennsylvania, U.S.A. in 2014, feeds for approximately six months by sucking phloem sap from trunks and limbs of tree of heaven, Ailanthus altissima, along with several native trees and woody vines. Basal trunk sprays of dinotefuran, a systemic neonicotinoid insecticide, are commonly used to reduce SLF densities and spread. Information on dinotefuran persistence and within-tree distribution can help identify optimal timing of annual basal trunk sprays, facilitating efficient use of available resources. We applied dinotefuran to 20 uninfested A. altissima trees in early April then periodically sampled foliage to monitor insecticide residues. Foliar dinotefuran residues averaged (± SE) 7.8 ± 1.1 and 6.3 ± 1.2 in July and August, respectively, then dropped significantly to 2.6 ± 0.5 ppm in September. In a second study, 20 A. altissima trees were similarly treated with dinotefuran basal trunk sprays in early June. Trees were felled to collect foliage and phloem from branches and the trunk in either mid-July or September. Foliar residues averaged 12.7 ± 1.3 and 14.6 ± 2.2 ppm in July and September, respectively. For trees felled in July, residues were detected in phloem collected from below the spray line on trunks of seven trees and above the spray line on three trees, averaging 8.6 ± 4.4 and 7.4 ± 2.9 ppm, respectively. In trees felled in September, phloem from below spray lines of seven trees averaged 3.7 ± 1.3 ppm but dinotefuran was not detected in phloem from above the spray line on any trees. Dinotefuran was not detected in phloem sampled from any branches in either July or September. Results suggest dinotefuran basal trunk sprays applied between late May and mid June should persist long enough to effectively control SLF late instars and adults.

Trunk Injection with Insecticides Manages Xylotrechus chinensis (Chevrolat) (Coleoptera: Cerambycidae)

Xylotrechus chinensis (Chevrolat) (Coleoptera: Cerambycidae) is a serious wood-boring insect of mulberry trees (Morus spp.). Larvae of this species enter the trunk of the tree and feed on woody tissues. Xylotrechus chinensis is endemic in several Asian countries, while, in the last decade, it invaded Europe. In the present work, we evaluated trunk injection against this pest. The systemic insecticides fipronil, imidacloprid, and spirotetramat were used in the trials. Abamectin was used as a positive control since it has been found to be effective for the management of X. chinensis. Imidacloprid and fipronil proved to be highly effective against this species in both years (9.5 and 12.1 exit holes/tree in 2021, 5.0 and 8.8 exit holes/tree in 2022, respectively), while spirotetramat was the least effective. The lowest mean number of exit holes was recorded when abamectin was applied in both years (4.7 exit holes/tree in 2021 and 3.3 exit holes/tree in 2022). The percentage of exit holes was reduced by 76.1, 71.8, and 85.6% in trees treated with imidacloprid, fipronil, and abamectin, respectively, after two years of application, while spirotetramat caused a 37.4% reduction. Trunk injection with imidacloprid, fipronil, and abamectin could be used against X. chinensis for long-term control of mulberry trees.

Species Diversity and Assemblages of Cerambycidae in the Aftermath of the Emerald Ash Borer (Coleoptera: Buptrestidae) Invasion in Riparian Forests of Southern Michigan

Extensive ash (Fraxinus spp.) mortality has been reported across much of the area in eastern North America invaded by emerald ash borer (Agrilus planipennis Fairmaire), but indirect effects of emerald ash borer invasion on native forest insects are not well-studied. We assessed cerambycid beetle (Coleoptera: Cerambycidae) species captured in baited cross-vane panel traps during the 2017 and 2018 growing seasons. Traps were placed in 12 riparian forest sites distributed across three watersheds selected to represent the temporal gradient of the emerald ash borer invasion from southeastern to southwestern Michigan. Although ash species originally dominated overstory vegetation in all sites, >85% of ash basal area has been killed by emerald ash borer. We captured a total of 3,645 beetles representing 65 species and five subfamilies. Species assemblages in southeast sites, with the longest history of emerald ash borer invasion, differed from those in south central and southwest Michigan, which were similar. These differences were largely due to three species, which accounted for >60% of beetle captures in southeast Michigan. Associations among site-related variables and beetle captures indicated cerambycid species assemblages were associated most strongly with abundance and decay stage of coarse woody debris. During both years, >90% of cerambycid species were captured by mid-summer but seasonal activity differed among and within tribes. Numbers of beetles captured by canopy and ground traps were similar but species richness was higher in canopy traps than ground traps. Results suggest inputs of emerald ash borer-killed ash can have temporally lagged, secondary effects on cerambycid communities.