Effects of Hemlock Woolly Adelgid Control Using Imidacloprid on Leaf-Level Physiology of Eastern Hemlock
Widespread mortality of eastern hemlock (<i>Tsuga canadensis</i> [L.] Carr.) has been occurring due to the introduction of hemlock woolly adelgid (<i>Adelges tsugae</i> Annand) (HWA), threatening millions of hectares of hemlock-dominated forests in the eastern United States....
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-06-01
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| Series: | Forests |
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| Online Access: | https://www.mdpi.com/1999-4907/14/6/1228 |
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| author | Kelly M. McDonald John R. Seiler Bingxue Wang Scott M. Salom Rusty J. Rhea |
| author_facet | Kelly M. McDonald John R. Seiler Bingxue Wang Scott M. Salom Rusty J. Rhea |
| author_sort | Kelly M. McDonald |
| collection | DOAJ |
| description | Widespread mortality of eastern hemlock (<i>Tsuga canadensis</i> [L.] Carr.) has been occurring due to the introduction of hemlock woolly adelgid (<i>Adelges tsugae</i> Annand) (HWA), threatening millions of hectares of hemlock-dominated forests in the eastern United States. HWA feeds at the base of needles and removes stored carbohydrates, which can impact leaf-level physiology, contributing to the decline of the tree. However, these physiological mechanisms in HWA-infested hemlocks are still not clearly understood. We investigated hemlock leaf physiology year-round at three forested sites with various degrees of infestation. At each site, half the trees were treated with imidacloprid (Merit<sup>®</sup> 2 F, Bayer, Kansas City, MO, USA) while the rest were left untreated. Imidacloprid is widely used to control HWA but can itself have phytotoxic effects. After one growing season, there was an increase in photosynthetic rates (7.5%, <i>p</i> = 0.0163) and stomatal conductance (7.1%, <i>p</i> = 0.0163) across sites in the trees treated with imidacloprid. After two years, the imidacloprid treatment also increased bud break from 22.5% to 88.7% at Fishburn (the most severely impacted site) and from 22.7% to 58.9% at Mountain Lake (the least impacted site), and slightly increased chlorophyll fluorescence for treated trees at Fishburn. Chemical treatment also slightly increased water use efficiency at Mountain Lake. These results suggest that HWA is causing tree mortality largely through a reduction in leaf area caused by decreasing bud break and also by a slight, but significant, reduction in leaf-level photosynthesis and stomatal conductance. |
| first_indexed | 2024-03-11T02:27:45Z |
| format | Article |
| id | doaj.art-8f65fa2d67f94d8f99a419cbffa89750 |
| institution | Directory Open Access Journal |
| issn | 1999-4907 |
| language | English |
| last_indexed | 2024-03-11T02:27:45Z |
| publishDate | 2023-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Forests |
| spelling | doaj.art-8f65fa2d67f94d8f99a419cbffa897502023-11-18T10:28:07ZengMDPI AGForests1999-49072023-06-01146122810.3390/f14061228Effects of Hemlock Woolly Adelgid Control Using Imidacloprid on Leaf-Level Physiology of Eastern HemlockKelly M. McDonald0John R. Seiler1Bingxue Wang2Scott M. Salom3Rusty J. Rhea4USDA National Institute of Food and Agriculture, 805 Pennsylvania Avenue, Kansas City, MO 64105, USADepartment of Forest Resources and Environmental Conservation, Virginia Tech, 228 Cheatham Hall, 310 West Campus Dr., Blacksburg, VA 24061, USAKey Laboratory Ecosystem Network Observation and Modeling, Chinese Academy of Sciences, Institute of Geographic Sciences and Natural Resources Research, Beijing 100101, ChinaDepartment of Entomology, Virginia Tech, 210 Price Hall, 170 Drillfield Dr., Blacksburg, VA 24061, USAUSDA Forest Service, Southern Research Station, 200 W.T. Weaver Boulevard, Asheville, NC 28804, USAWidespread mortality of eastern hemlock (<i>Tsuga canadensis</i> [L.] Carr.) has been occurring due to the introduction of hemlock woolly adelgid (<i>Adelges tsugae</i> Annand) (HWA), threatening millions of hectares of hemlock-dominated forests in the eastern United States. HWA feeds at the base of needles and removes stored carbohydrates, which can impact leaf-level physiology, contributing to the decline of the tree. However, these physiological mechanisms in HWA-infested hemlocks are still not clearly understood. We investigated hemlock leaf physiology year-round at three forested sites with various degrees of infestation. At each site, half the trees were treated with imidacloprid (Merit<sup>®</sup> 2 F, Bayer, Kansas City, MO, USA) while the rest were left untreated. Imidacloprid is widely used to control HWA but can itself have phytotoxic effects. After one growing season, there was an increase in photosynthetic rates (7.5%, <i>p</i> = 0.0163) and stomatal conductance (7.1%, <i>p</i> = 0.0163) across sites in the trees treated with imidacloprid. After two years, the imidacloprid treatment also increased bud break from 22.5% to 88.7% at Fishburn (the most severely impacted site) and from 22.7% to 58.9% at Mountain Lake (the least impacted site), and slightly increased chlorophyll fluorescence for treated trees at Fishburn. Chemical treatment also slightly increased water use efficiency at Mountain Lake. These results suggest that HWA is causing tree mortality largely through a reduction in leaf area caused by decreasing bud break and also by a slight, but significant, reduction in leaf-level photosynthesis and stomatal conductance.https://www.mdpi.com/1999-4907/14/6/1228<i>Adelges tsugae</i>chlorophyll fluorescenceMeritneedle gas exchangephotosynthesis<i>Tsuga canadensis</i> |
| spellingShingle | Kelly M. McDonald John R. Seiler Bingxue Wang Scott M. Salom Rusty J. Rhea Effects of Hemlock Woolly Adelgid Control Using Imidacloprid on Leaf-Level Physiology of Eastern Hemlock Forests <i>Adelges tsugae</i> chlorophyll fluorescence Merit needle gas exchange photosynthesis <i>Tsuga canadensis</i> |
| title | Effects of Hemlock Woolly Adelgid Control Using Imidacloprid on Leaf-Level Physiology of Eastern Hemlock |
| title_full | Effects of Hemlock Woolly Adelgid Control Using Imidacloprid on Leaf-Level Physiology of Eastern Hemlock |
| title_fullStr | Effects of Hemlock Woolly Adelgid Control Using Imidacloprid on Leaf-Level Physiology of Eastern Hemlock |
| title_full_unstemmed | Effects of Hemlock Woolly Adelgid Control Using Imidacloprid on Leaf-Level Physiology of Eastern Hemlock |
| title_short | Effects of Hemlock Woolly Adelgid Control Using Imidacloprid on Leaf-Level Physiology of Eastern Hemlock |
| title_sort | effects of hemlock woolly adelgid control using imidacloprid on leaf level physiology of eastern hemlock |
| topic | <i>Adelges tsugae</i> chlorophyll fluorescence Merit needle gas exchange photosynthesis <i>Tsuga canadensis</i> |
| url | https://www.mdpi.com/1999-4907/14/6/1228 |
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