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Benton EP, Grant JF, Webster RJ, Cowles RS, Lagalante AF, Saxton AM, Nichols RJ, Coots CI. Hemlock Woolly Adelgid (Hemiptera: Adelgidae) Abundance and Hemlock Canopy Health Numerous Years After Imidacloprid Basal Drench Treatments: Implications for Management Programs. J Econ Entomol 2016; 109:2125-2136. [PMID: 27435928 DOI: 10.1093/jee/tow160] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 06/19/2016] [Indexed: 06/06/2023]
Abstract
Hemlock woolly adelgid (Adelges tsugae [Annand]), an invasive insect in the eastern United States, has caused widespread decline of eastern hemlock, Tsuga canadensis (L.) Carriére. Imidacloprid basal drench treatments were assessed 4-7 yr after a single treatment to determine hemlock woolly adelgid population suppression and effects on hemlock canopy health. The effects of sampling site, years post-treatment, and hemlock diameter at breast height (DBH) size classes were evaluated relative to imidacloprid treatment on hemlock woolly adelgid populations and hemlock canopy health characteristics. The influence of hemlock woolly adelgid populations on canopy health characteristics was also assessed. Imidacloprid treatments resulted in low-level hemlock woolly adelgid populations 7 yr post-treatment. Hemlock woolly adelgid was present on more hemlocks 7 yr compared with 4-6 yr post-treatment. Smaller hemlocks, dosed with 0.7 g active ingredient (AI)/2.5 cm DBH, had higher populations of hemlock woolly adelgid than the largest size class, which were treated at twice that dosage. Concentrations of imidacloprid and its olefin metabolite below the LC50 were sufficient for suppression of hemlock woolly adelgid populations, which suggests an additive effect of imidacloprid and olefin that compounds hemlock woolly adelgid mortality over many generations. Hemlock woolly adelgid populations observed in this study were too low to have an observable effect on hemlock canopy health, indicating that application intervals of up to 7 yr may be adequate to protect hemlocks.
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Affiliation(s)
- E P Benton
- Department of Entomology and Plant Pathology, 370 Plant Biotechnology Bldg., the University of Tennessee, Knoxville, TN 37996 (; ; ) University of Georgia-Tifton, 2360 Rainwater Rd., Tifton, GA 31793
| | - J F Grant
- Department of Entomology and Plant Pathology, 370 Plant Biotechnology Bldg., the University of Tennessee, Knoxville, TN 37996 (; ; )
| | - R J Webster
- Great Smoky Mountains National Park, 107 Park Headquarters Rd., Gatlinburg, TN 37738 (, )
| | - R S Cowles
- The Connecticut Agricultural Experiment Station, 153 Cook Hill Rd., Windsor, CT 06095
| | - A F Lagalante
- Department of Chemistry, Villanova University, 800 Lancaster Ave., Villanova, PA 19085-1699
| | - A M Saxton
- Department of Animal Science, the University of Tennessee, 232 Brehm Animal Science Bldg., Knoxville, TN 37996
| | - R J Nichols
- Great Smoky Mountains National Park, 107 Park Headquarters Rd., Gatlinburg, TN 37738 (, )
| | - C I Coots
- Department of Entomology and Plant Pathology, 370 Plant Biotechnology Bldg., the University of Tennessee, Knoxville, TN 37996 (; ; )
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Benton EP, Grant JF, Webster RJ, Nichols RJ, Cowles RS, Lagalante AF, Coots CI. Assessment of Imidacloprid and Its Metabolites in Foliage of Eastern Hemlock Multiple Years Following Treatment for Hemlock Woolly Adelgid, Adelges tsugae (Hemiptera: Adelgidae), in Forested Conditions. J Econ Entomol 2015; 108:2672-82. [PMID: 26470386 DOI: 10.1093/jee/tov241] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 07/19/2015] [Indexed: 05/04/2023]
Abstract
Widespread decline and mortality of eastern hemlock, Tsuga canadensis (L.) Carrière, have been caused by hemlock woolly adelgid, Adelges tsugae (Annand) (HWA) (Hemiptera: Adelgidae). The current study is a retrospective analysis conducted in collaboration with Great Smoky Mountains National Park (GRSM) to determine longevity of imidacloprid and its insecticidal metabolites (imidacloprid olefin, 5-hydroxy, and dihydroxy) in GRSM's HWA integrated pest management (IPM) program. Foliage samples were collected from three canopy strata of hemlocks that were given imidacloprid basal drench treatments 4-7 yr prior to sampling. Foliage was analyzed to assess concentrations in parts per billion (ppb) of imidacloprid and its metabolites. Imidacloprid and its olefin metabolite were present in most, 95 and 65%, respectively, branchlets 4-7 yr post-treatment, but the 5-hydroxy and dihydroxy metabolites were present in only 1.3 and 11.7%, respectively, of the branchlets. Imidacloprid and olefin concentrations significantly decreased between 4 and 7 yr post-treatment. Concentrations of both imidacloprid and olefin were below the LC50 for HWA 5-7 yr post-treatment. Knowledge of the longevity of imidacloprid treatments and its metabolite olefin can help maximize the use of imidacloprid in HWA IPM programs.
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Affiliation(s)
- E P Benton
- Department of Entomology and Plant Pathology, 370 Plant Biotechnology Building, The University of Tennessee, Knoxville, TN 37996.
| | - J F Grant
- Department of Entomology and Plant Pathology, 370 Plant Biotechnology Building, The University of Tennessee, Knoxville, TN 37996
| | - R J Webster
- Great Smoky Mountains National Park, 107 Park Headquarters Rd., Gatlinburg, TN 37738
| | - R J Nichols
- Great Smoky Mountains National Park, 107 Park Headquarters Rd., Gatlinburg, TN 37738
| | - R S Cowles
- The Connecticut Agricultural Experiment Station, 153 Cook Hill Rd., Windsor, CT 06095
| | - A F Lagalante
- Department of Chemistry, 800 Lancaster Ave., Villanova University, Villanova, PA 19085-1699
| | - C I Coots
- Department of Entomology and Plant Pathology, 370 Plant Biotechnology Building, The University of Tennessee, Knoxville, TN 37996
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