JOBNAME: horts 41#7 2006 PAGE: 1 OUTPUT: October 25 00:32:17 2006 tsp/horts/127877/01585 PLANT PATHOLOGY HORTSCIENCE 41(7):1629–1634. 2006. Desertwillow or desertcatalpa, Chilopsis D. Don., is a monotypic genus related to Catalpa Chilopsis Catalpa. Chilopsis linearis (Cav.) Sweet is a Susceptibility of , , and small to medium-sized tree with willow-like leaves and attractive flowers in summer found Hybrids to Powdery Mildew and in washes and arroyos in desert regions of the southwestern United States, from southern Catalpa Sphinx Larvae California to Texas, and south-central Mexico (Henrickson, 1985). The species and its culti- Richard T. Olsen1,4 and Thomas G. Ranney2 vars are grown throughout its native range and Department of Horticultural Science, Mountain Horticultural Crops adjacent regions and are valued for drought Research and Extension Center, North Carolina State University, Fletcher, tolerance and attractive flowers (Dirr, 1998; Henrickson, 1985; Tipton, 1987). NC 28732-9244 Catalpa and Chilopsis are very similar but Charles S. Hodges3 are differentiated by number of stamens, two in Catalpa vs. four in Chilopsis, and leaf Department of Plant Pathology, North Carolina State University, Raleigh, morphology, large ovate to cordate leaves in NC 27695-7616 Catalpa vs. linear to lanceolate leaves in Additional index words. ·Chitalpa tashkentensis, Macrocatalpa, Tecomeae, Bignoniaceae, Chilopsis. Traditional classifications have placed them in the large, pan-tropical tribe Erysiphe elevata, Ceratomia catalpae, disease resistance Tecomeae Endl. (Henrickson, 1985). How- Abstract. A diverse collection of germplasm representing 24 taxa from Catalpa sect. ever, this tribe was shown recently to be Catalpa Paclt and sect. Macrocatalpa Grisebach, Chilopsis D. Don, and ·Chitalpa Elias & paraphyletic, suggesting that the tribe be di- Wisura were screened for susceptibility to powdery mildew (PM) incited by Erysiphe vided with Catalpa (both sections) and Chi- elevata (Burr.) U. Braun & S. Takam and feeding by catalpa sphinx larvae (CSL), lopsis forming a new tribe sister to the Ceratomia catalpae (Boisduval). PM screening was conducted on plants grown in Oroxyleae Gentry (Olmstead, unpublished a lathhouse (50% shade) in 2004 and a gravel pad (100% sun) in 2005. The PM causal data; Spangler and Olmstead, 1999). Interge- organism was identified as E. elevata both years. Disease incidence and severity were neric hybrids between Chilopsis linearis and recorded at 2-week intervals for 6 weeks and used to calculate area under the disease Catalpa bignonioides bred by Rusanov (1964) progress curves (AUDPC) for each year. North American Catalpa in sect. Catalpa, were introduced into the United States in 1977 Chilopsis, and ·Chitalpa taxa were all moderately to highly susceptible to PM. Chinese and formally described by Elias and Wisura Catalpa in sect. Catalpa and West Indian species in sect. Macrocatalpa were resistant to (1991) as ·Chitalpa tashkentensis. ·Chitalpa PM. Hybrids between North American and Chinese Catalpa in sect. Catalpa varied in has performed well in arid climates, but susceptibility, indicating transmission of partial resistance to PM. No differences in suffers in more humid climates from severe survival or growth were found in a no-choice feeding study with CSL reared on taxa from powdery mildew (PM) infections (Dirr, 1998) Chilopsis, ·Chitalpa, or either section of Catalpa. Future breeding of ·Chitalpa can use and in eastern North America from herbivory sources of PM resistance identified in this study, but a source of resistance to CSL was not by catalpa sphinx moth larvae, Ceratomia found. catalpae (Lepidoptera: Sphingidae) (T.G. Ranney, personal observation). Powdery mildews (PM) are obligate fun- gal parasites (Ascomycetes) characterized by The genus Catalpa Scop. (Bignoniaceae (Alabama to western Florida) and northern epiphytic white mycelium that often cause Juss.) is composed of 11 species in two well- catalpa, C. speciosa (Ward. ex Barn.) Ward. distortions of new growth, chlorosis, necro- defined sections, Catalpa and Macrocatalpa, ex Engelm., is native to the south-central sis, and premature leaf fall (Braun, 1987), differentiated by leaf morphology and seed United States. Both are cultivated as well as limiting both growth and aesthetic qualities characteristics as well as geographic distri- naturalized in many urban areas of the eastern of infected plants. Seven different species of bution (Paclt, 1952). Section Catalpa con- United States (Rehder, 1940). Section Mac- PM have been identified on Catalpa spp. with tains six species of deciduous trees with rocatalpa is comprised of five species of two host-specific to Catalpa: Erysiphe cata- a disjunct distribution between East Asia semievergreen trees restricted to the West lpae Simonyan and E. elevata (syn. Micro- (four species) and eastern North America Indies. These species are poorly represented sphaera elevata Burr.) (Ale-Agha et al., (two species). All species from this section in cultivation, with the exception of C. long- 2004; Braun, 1987; Braun et al., 2002; Farr are in cultivation except C. tibetica Forrest, issima (Jacq.) Dum.-Cours. (Haitian yoke- et al., 1989). Of the two Catalpa-specific but only the two North American species are wood), which is cultivated throughout the PMs, only E. elevata has been reported in commonly cultivated as ornamental trees. West Indies as an important landscape and North America, with E. catalpae currently Southern catalpa, C. bignonioides Walt., is timber species and in Florida and Hawaii for restricted to Europe and Asia (Braun, 1987; native to the southeastern United States landscapes (Francis, 1990). Sinclair et al., 1987). Received for publication 24 Apr. 2006. Accepted Plantations, Cornell University, Ithaca, N.Y.; Lynch, Irene Palmer, and staff of the Mountain for publication 22 July 2006. Benoit Jonckheere and Don Evans, Fairchild Horticultural Crops Research and Extension Cen- This research was funded, in part, by the North Tropical Botanic Garden, Coral Gables, Fla.; ter is greatly appreciated. We thank William Carolina Agricultural Research Service (NCARS), Mark Krautman, Heritage Seedlings, Salem, Swallow for statistical and James F. Walgenbach Raleigh, N.C.; North Carolina Association of Nurs- Ore.; the JC Raulston Arboretum, Raleigh, N.C.; for entomologic advice. From a dissertation sub- erymen, Inc., Raleigh, N.C.; and J. Frank Schmidt Veta Bonnewell, Morton Arboretum, Lisle, Ill.; mitted by R.T.O. in partial fulfillment of the Family Charitable Foundation, Boring, Ore. Bill Carson, Native Texas Nursery, Austin, requirements for the PhD degree. Use of trade names in this publication does not imply Texas; Andrew Bunting, Scott Arboretum, 1Current address: Floral and Nursery Plants Re- endorsement by the NCARS of products named nor Swarthmore, Pa.; the Sir Harold Hillier Gardens, search Unit, USDA-ARS, US National Arboretum, criticism of similar ones not mentioned. Hampshire, UK; and Dawn Stover and David 3501 New York Ave. NE, Washington, DC. We gratefully acknowledge Tom Ward, Arnold Creech, Mast Arboretum, Stephen F. Austin 2Professor. Arboretum, Harvard University, Jamaica Plain, University, Nacogdoches, Texas, for providing 3Professor emeritus. Mass.; Alessandro Chiari, Brooklyn Botanic Gar- germplasm used in our studies. Technical assis- 4To whom reprint requests should be addressed; den, Brooklyn, N.Y.; Mary Hirshfeld, Cornell tance of Thomas Eaker, Joel Mowrey, Nathan e-mail [email protected]. HORTSCIENCE VOL. 41(7) DECEMBER 2006 1629 JOBNAME: horts 41#7 2006 PAGE: 2 OUTPUT: October 25 00:32:17 2006 tsp/horts/127877/01585 Catalpa sphinx moth is distributed Catalpa sp. #2 (n = 3), and C. bungei var. a given plant at a given observation date throughout the eastern United States from heterophylla (n = 2). (Seem, 1984). Then, AUDPC represents the New York to Florida west to Texas and Iowa Catalpa bignonioides stock plants were cumulative disease intensity for a given plant overlapping with the native and naturalized grown separately in the lathhouse and al- over the length of the study (Jeger and range of natural host plant species C. bigno- lowed to develop PM infections naturally. Viljanen-Rollinson, 2001). Data for each nioides and C. speciosa (Baerg, 1935). Pre- Beginning on 4 Aug. 2004, infected stock year were analyzed separately. Differences vious studies confirmed the suitability of plants were placed in and around study between taxa were compared using analysis Chinese Catalpa species as a food source plants and shaken over the study plants to of variance (PROC GLM; SAS version 8.02; for catalpa sphinx larvae (CSL) (Baerg, 1935; release conidia every other day for 1 week SAS Institute, Cary, N.C.) and means sepa- Bowers, 2003). Host plant species signifi- (total 4·) to supplement natural inocula- rated using Fisher protected least significant cantly affected larval growth (fresh weight), tion. Powdery mildew incidence (I) and difference (LSD)ata = 0.05. but survival was unaffected for larvae reared severity (S) were recorded for each repli- Catalpa sphinx moth larvae screening. A on C. bignonioides, C. bungei C.A. Mey, cate once every 2 weeks for a total of four no-choice feeding study, with the addition of C. fargesii Bureau, C. ovata G. Don, and observation dates. Incidence (I) represented C. linearis ÔRegalÕ, was conducted in Summer C. speciosa (Bowers, 2003). Ceratomia cat- the percentage of leaves infected per plant 2005. On 22 June, fourth and fifth instars alpae larvae sequester catalpol,