Arboriculture & Urban Forestry 39(5): September 2013 elms based on their relative susceptibility or resistance to all 12 pests evaluated since 2006. That summary, too, is reported herein. METHODS AND MATERIALS The main study site was an open, grassy area on Maury silt loam soil adjacent to the Arboretum and State Botanical Garden of Kentucky (Lexington, Kentucky) (38°1’N, 84°30’W; eleva- tion 302 m). Five replicates of 20 elm cultivars, including North American, Asian, and European species and hybrids (Table 1) were planted in a randomized complete block in rows spaced 7.6 m apart, with 7.6 m between trees within rows and about 50 m between replicates. Seventeen cultivars were planted in spring 2005; three others were planted in randomized spaces left in each block in spring 2006 or 2007. The trees were obtained from nurseries as bare-root transplants and ranged from 1.5 to 2.4 m height at time of planting. They were staked, watered as needed, and mulched over grass that had been killed with glypho- sate herbicide. Cultivar names and provenance are summarized in Table 1. Leaf characteristics (mean area, number per shoot, pubescence) were previously summarized (Condra et al. 2010). Pest Resistance Evaluations Three species of sap-feeding scale insects colonized trees at the study site. Their numbers were assessed by inspect- ing each tree on multiple dates. For some of the taller trees, 237 observers stood on a step ladder or truck tailgate to reach and sample sufficient numbers of representative branches. European fruit lecanium, Parthenolecanium corni (Hemip- tera: Coccidae), was abundant enough to provide data from three growing seasons (2010–2012). Five twigs were randomly select- ed from throughout the canopy of each tree; then beginning at the previous year’s node the number of adult scales was counted on a 30-cm long section of each twig. Data were standardized to number of scales per 1.0 m of twig length. Counts were taken over 2–3 days in early July in 2010 and 2011, and in June 2012. European elm scale, Eriococcus spuria (Hemiptera: Eriococ- cidae), was abundant enough to census in 2011 and 2012. Adult scales were counted on five 30 cm-long twigs per tree as pre- viously described. In addition, because E. spuria also infested bark of the trunk and scaffold limbs, two observers standing on opposite sides of each tree inspected bases of those branches and main trunk of each tree to 2 m height, and counted scales spotted in 30 seconds, taking care not to count particular scales more than once. Counts from the two methods were pooled for analysis. Sampling dates were the same as for P. corni. Cottony maple scale, Pulvinaria innumerabilis (Hemiptera: Coccidae), was first noticed on the trees in 2012. Two observers slowly circled each tree on June 7–8 and together counted all of the distinctive white scales through the canopy. A mottled gray, leaf-notching weevil was found feeding on elms at the study site in 2010 (Figure 1). Specimens were sent Table 1. Elm species hybrids and cultivars evaluated for insect resistance in Lexington, Kentucky, U.S., from 2006 to 2012 with geographical origins and selected leaf characteristics. Species or parentage U. americana Cultivar name Valley Forge Princeton Jefferson New Harmony U. parvifolia U. propinqua U. wilsoniana U. pumila × japonica U. japonica × wilsoniana U. pumila × japonica × wilsoniana U. carpinifolia × pumila × wilsoniana U. glabra × carp. × pumila × wilsoniana U. carp × parvifolia U. glabra × carp × pumila U. glabra × carpinifolia z Lewis & Clark Prairie Expedition Emer II Allee Athena Classic Lacebark Everclear Lacebark Emerald Sunshine Prospector Morton Plainsman Vanguard New Horizon Morton Red Tip Danada Charm Morton Accolade Morton Glossy Triumph Morton Stalwart Commendation Patriot Frontier Homestead Pioneer Abbr. VF PN J NH PE EA A E ES PR MP Nh MR M MG MS PT F H PI Japan, China, Korea [A] Japan [A] China [A] A × A A × A A × A × A A × A × A E × A E × A E × E × A E × E Parental species (native ranges) not listed: U. carpinifolia (Europe, N. Africa); U. glabra (Europe, W. Asia); U. pumila (Siberia, China, Korea); and U. davidiana var. japonica (China, Japan, Korea). ©2013 International Society of Arboriculture Native rangez N. America [NA]
September 2013
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
