Nectriella (Kutilakesa) Pironii, a Pathogen of Ornamental Plants1 S

3. Davis, S. H., M. R. Harrison, B. C. Moser, D. Durkin, R. L. applied growth regulators on height control of poinsettia. Hort- Flannery, F. E. Jensen, P. J. Kirschling, J. L. Peterson, W. J. Science 11:373-374. Roberts, J. N. Sacalis, H. T. Streu, T. M. Vasvary, and W. Welker. 9. USD A. 1980. Flowers and foliage plants. Production and sales, 1978 1975. Consumers prefer certain types of mini-poinsettias. Florists' and 1979. Intentions for 1980. USDA Statistical Rept. Sen. SpCr 6-1 Rev. 157:23. (80). 27 pp. 4. , , and . 1975. Growing pinched 10. Wilfret, G. J., and B. K. Harbaugh. 1977. Evaluation of poinsettia poinsettias in 4-inch pots. Florists* Rev. 157:31, 71-72. cultivars grown on two irrigation systems. Proc. Fla. State Hort. 5. Freeman, R. N. 1974. Poinsettias and capillary watering. Florists' Soc. 90:309-311. Rev. 155:27-29. 11. 1978. Height regulation of poinsettia with a growth re- 6. Hammer, A., and R. W. Langhans. 1972. Something new for tardant incorporated in the soil medium. Proc. Fla. State Hort. Soc. capillary watering. Florists' Rev. 150:15, 54. 91:220-222. 7. Larson, R. A., and B. G. Hilliard. 1973. Mini-multi-flowering 12. , B. K. Harbaugh, and T. A. Nell. 1978. Height control poinsettias. N. Carolina Flower Growers Bull. 17:1-4. of "Pixie" poinsettia with a granular formulation of ancymidol. 8. Tjia, B., S. Ohpanayikool, and J. Buxton. 1976. Comparison of soil HortScience 13:701-702. Proc. Fla. State Hort. Soc. 93:218-219. 1980. NECTRIELLA (KUTILAKESA) PIRONII, A PATHOGEN OF ORNAMENTAL PLANTS1 S. A. Alfieri, Jr., C. L. Schoulties, and N. E. El-Gholl Nees cv. Dania, Cordyline australis Hook., Dieffenbachia Division of Plant Industry, picta Schott cv. Perfection, Dracaena marginata Lam., Fatsia Florida Department of Agriculture and Consumer Services japonica Decne. 8c Planch., Ficus elastica Roxb. cv. Decora P. O. Box 1269, Schrijveriana, Philodendron sp. cv. Red Emerald—were se Gainesville, FL 32602 lected for inoculation and testing for susceptibility to Kutilakesa pironii. Aphelandra squarrosa, the zebra plant, Abstract. The fungus, Nectriella (Kutilakesa) pironiif was included as a standard in this trial because of its rela causes stem and leaf galls, corky proliferations, and cankers tively high level of susceptibility to this pathogen as de of a wide host range of woody and herbaceous ornamental termined in previous studies (1, 2, 3). The cultivars of plants. Our plant disease records and data collected from croton (Codiaeum variegatum) selected for comparative artificial inoculations indicate that 42 genera belonging to susceptibility were 'Bravo', 'Elaine', 'Norma', and 'Stoplight'. 26 families in 16 orders are susceptible to this wound All of the test plants were large, vigorous, mature plants. pathogen. Seven of the more popular foliage plants were All species were inoculated via two methods—a transverse cut tested for susceptibility to the pathogen and results indicated through the stems of branch terminals with a sterile pruning varying levels of resistance. Croton (Codiaeum variegatum), tool and an oblique incision approximately 2-3 mm deep and one of the more common and economically important hosts 5-7 mm long made with a sterile scalpel at the stem nodes. of this fungus, displayed a high degree of varietal sus Each test plant species or variety was inoculated with five ceptibility in inoculation tests. transverse cuts and 25 incisions, with a like number serving as controls, except crotons which were given 30 incisions. Two sources of inocula were used in this study, one Nectriella pironii Alfieri & Samuels has been recently from A. squarrosa designated Isolate A-7 and used as the described (3), along with its imperfect state Kutilakesa pathogen for all foliage plants except croton and the other pironii Alfieri (1), and has been reported as a wound patho isolate derived from C. variegatum cv. Norma utilized in gen on a number of woody and other ornamental plants the varietal susceptibility of crotons. The two isolates were (2). N. pironii causes stem and leaf galls, corky prolifera grown on PDA (broth of 200 g of boiled fresh Irish potatoes tions, and cankers on an extensive host range of woody and supplemented with 20 g dextrose, 1 g KH2PO4 and 18 g herbaceous ornamental plants. Our plant disease records in Difco agar, made up to 1 liter with deionized water) for 4 the Division of Plant Industry, Florida Department of Agri weeks at 25C under 12-hour periods of alternating light culture and Consumer Services, and data developed from (fluorescent light, Westinghouse F20 T12/CW at an in experimental inoculations indicate that 42 genera belonging tensity of approximately 1400 lux) and dark. to 26 families in 16 orders are susceptible to this wound Inoculation of the transverse cut stems consisted of pathogen. The abundance of fungus inoculum on diseased placing one drop of approximately 0.05 ml of spore suspen plants, the ever-present mycophagous mites, and horti sion containing 5.36 x 106 conidia per ml of deionized water, cultural practices in ornamental plant production, are im on the freshly cut surface of the stem. Stem incisions were portant factors of this disease phenomenon which could inoculated by inserting a 2 mm diameter PDA plug result in excessively high incidence of this disease, hence bearing sporodochia of the fungus into the nodal incision. result in substantial losses due to poor, unthrifty, nonsale- All inoculated plants plus the controls were placed on a able plants. greenhouse bench and observations made at 3-week intervals The purpose of this study was to determine the host for 12 weeks, at which time final readings were made. Gall range of some of the more popular foliage ornamental formation was measured as proliferated, callus tissue at plants and the varietal susceptibility of four cultivars of the sites of inoculation, with subsequent re-isolation of the croton (Codiaeum variegatum Blume), which has shown causal pathogen. high susceptibility among some of its cultivars. Materials and Methods Results and Discussion Seven foliage ornamental plants-Aphelandra squarrosa The degree of corky proliferation of gall tissue varied & r among the plants tested. Aphelandra produced galls up to iContribution No. 494, Bureau of Plant Pathology. 3 mm in diameter at cut surfaces and up to 5 mm at in- 218 Proc. Fla. State Hort, Soc. 93: 1980. cision sites; Dieffenbachia—no gall formation at cut surfaces formation in 'Bravo', 'Norma', and 80% in 'Stoplight'. These and galls up to 3 mm in diameter with incisions; Dracaena- results are given in Table 2. None of the controls produced no galls at cut surfaces and one 3-4 mm gall at one incision any galls, nor was the fungus isolated where slight callus site; Fatsia—galls up to 4 mm in diameter at cut surfaces development occurred, which undoubtedly were normal re and up to 14 mm at incision sites; Ficus— dry necrosis de sponses to injury. veloped rather than gall formation at transverse cuts and Table 2. Reactions of four cultivars of croton (Codiaeum variegatum) slight callus tissue formation at incision sites; Philodendron to stem wound inoculations with Kutilakesa pironii. —slight tissue proliferation at both the transverse cut sur faces and incision sites; and Cordyline—resulted in no tissue proliferation or gall formation. Results of inoculation and Time Gall size symptom reaction in the production of galls with re-isola Cultivar 3 wk 6wk 9 wk 12 wk (diam.) tion of the pathogen are shown in Table 1. Bravo 21/30 28/30 30/30 30/30 5-14 mm Table 1. Stem wound inoculation of seven foliage ornamental plants Elaine 3/30 4/30i 5/30 6/30 4-5 mm with Kutilakesa pironii. Norma 23/30 28/30' 30/30 30/30 4-14 mm Stoplight 13/30 23/30 24/30i 24/30 3-9 mm Number Method of Symptom infected/ This study indicates that though this fungus has a rela Host plant inoculation reaction inoculated tively wide host range, differences in host susceptibility do exist. Whereas most of the foliage ornamentals tested in Aphelandra Cut Galls, 1-3 mm 2/5 this study were more or less highly susceptible, our data squarrosa cv. Dania Incision Galls, 2-5 mm 25/25 under the foregoing experimental conditions of this study Cordyline Cut None 0/5 clearly suggest that Cordyline australis is highly resistant or australis Incision None 0/25 Dieffenbachia Cut None 0/5 immune and Dracaena marginata, likewise highly resistant. picta cv. Perfection Incision Corky proliferation, 20/25 Further, the transverse cut method of inoculation, simulat 1-3 mm ing a common method of ornamental plant propagation, is Dracaena Cut None 0/5 not as conducive for infection as the incision method of marginata Incision Gall, 3-4 mm, on 1/25 young stem inoculation. There also appears to be a fairly high level of Fatsia Cut Galls, 1-4 mm 4/5 resistance in the croton cultivar 'Elaine', a noteworthy factor, japonica Incision Galls, 1-14 mm 19/23 particularly notable when contrasted to the relatively high Ficus elastica Cut Limited necrosis 5/5 cv. Decora susceptibility of 'Bravo', 'Norma' and 'Stoplight' to this Schrijveriana Incision Callus tissue, no galls 15/25 wound pathogen. Philodendron sp. Cut Slight callus 5/5 cv. Red Emerald formation Incision Slight callus 15/25 Literature Cited formation 1. Alfieri, S. A., Jr. 1979. Kutilakesa pironii sp. nov., a stem gall- and canker-inciting fungus, new to the United States. Mycotaxon 10:217-218. The varietal reaction to incision inoculation of the four 2. , J. F. Knauss, and C. Wehlburg. 1979. A stem gall- and cultivars of croton indicates differences exist in susceptibility canker-inciting fungus, new to the United States.

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