PHSI Interception PRA for Puccinia hemerocallidis update prepared by David Jones, CSL; 17/02/05;

First PRA completed on 10/01/02; PPP 9860

05-11627 (rev of 02-9179)

P PM point 8.2

SUMMARY PEST RISK ANALYSIS FOR UK INTERCEPTIONS
Question / Answer
1. Name of fungal pest:
Teleomorph: Genus, species, var., f.sp. /

Puccinia hemerocallidis

Synonym(s): Genus, species, var., f.sp. / Dicaeoma hemerocallidis, Aecidium patriniae, Puccinia funkiae, Uredo hostae, Puccinia hostae
Anamorph: Genus, species, var., f.sp.
Synonym(s): Genus, species, var., f.sp.
Common name for disease / Daylily rust
Special notes on taxonomy or nomenclature / Transchel in 1913 (Hiratsuka, 1992) was the first to prove the relation between the aecia on leaves of Patrinia rupestris and P. scabiosaefolia to the uredinia and telia on leaves of Hemerocallis minor. Hiratsuka in 1938 was the first to report successful inoculations between the aecial state of this species on Patrinia scabiosaefolia and the uredinial and telial states on leaves of Hemerocallis disticha (Hiratsuka, 1992). Hosta spp. have been reported as uredinal/telial hosts in Japan (Hiratsuka, 1992). However, Hosta has been found to be affected in the USA (Schubert and Leahy, 2001) and is now not thought to be a host in Japan (Yoshitaka, 2003).
Primary pathogen (Y/N) / Y
Weak pathogen (Y/N) / N
Saprophyte (Y/N) / N
2. (ai) Does it occur in the UK?
No (C. Lane, CSL, 2001, pers. comm.)
(aii) Has it been intercepted before on this host in the UK ?
The pathogen was intercepted in 2001 and 2002 on daylilies imported from the USA.
(aiii) Has it been recorded before on this host in the UK?
No (C.Lane, CSL, 2001, pers. comm.)
2 (b). Is there any other reason to suspect that the pest is already established in the
UK?
No, but there has not been a comprehensive survey of nurseries growing daylilies
3. EC Directive Status? (Annex or not listed)
Not listed
4. EPPO Status? Present on Alert List
5. What are its host plants?
5.  (a). Highlight crop plants grown commercially, including those of environmental or amenity value, in the UK (and EU/EPPO) (include figures for potential yield/quality losses):
Puccinia hemerocallidis is a heteroecious rust. Species in the genera Hemerocallis, a common amenity plant in Europe, are uredial/telial hosts. Hosta (Liliaceae) has also been described as an uredial/telial host in Asia (Hiratsuka, 1992). However, this has not been proven (Yoshitaka, 2003) and the rust has never been seen on Hosta in the USA (Schubert and Leahy, 2001). Species in the genus Patrinia (Valerianaceae) are spermagonial/aecial hosts.
Uredospores released from Hemerocallis can perpetuate the rust on this host. Germinating teliospores on Hemerocallis produce basidiospores capable of initiating infection on Patrinia spp.. Aeciospores from infected Patrinia spp. are capable of initiating infections on Hemerocallis.
5. (b). Are any of the host plants of forestry importance?
No
6. What is its present geographical distribution?
Asia: China; Japan; Korea; Russia - Sakhalin, Kuriles, Siberia; Taiwan
(Hernández et al., 2002; Hiratsuka, 1992; Schubert and Leahy, 2001).
Australia/Pacific: Australia - Queensland (EPPO, 2002).
North America : Canada (Anon., 2002); USA - Alabama, California, Florida, Georgia,
Mississippi, Minnesota, South Carolina, Tennessee, Texas (Schubert and Leahy, 2001)
plus Arkansas, Connecticut, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana,
Maryland, Michigan, Missouri, Nebraska, New Hampshire, New Jersey, New York,
North Carolina, Ohio, Oregon, Pennsylvania, Rhode Island, Virginia, Wisconsin
(Anon., 2002) plus Hawaii (Hernández et al., 2002).
Central America: There is indirect evidence that the rust may be present in Costa Rica as
daylilies imported from Costa Rica have been diagnosed with the rust on arrival in
Miami (Hernández et al., 2002; Schubert and Leahy, 2001).
Present in EU (specify countries): Not reported
Present in EPPO region (specify countries): Not reported
7. Does it appear capable of establishing in the UK/EU/EPPO?
(a) outdoors? Daylilies are commonly grown garden plants and are hardy perennials. The rust is capable of surviving on daylily alone; no other host species is required for it to perennate. Daylily is a common amenity plant in Europe. Daylily rust has been recorded in climates as diverse as those in Siberia and Florida and would be expected to be capable of establishment in the UK and the EU/EPPO region where Hemerocallis spp. are grown. Experimental work in the USA has shown that uredospores can germinate on potato dextrose agar between 10°C and 30°C. Germination was not observed at 4°C and 34°C and it is thought that summer temperatures in the south of the USA may not favour infection (-Buck and Williams-Woodward, 2001; Mueller et al., 2002). High temperatures in southern Europe during summer may also inhibit infection.
(b) on protected crops? Daylily rust has been found on plants growing in nurseries in the USA. The second detection in the UK in 2002 was on imported plants growing in a polytunnel. Some plants may have been under glass or shadecloth, but there is no information to confirm this possibility
8. What is its potential likely to be as a pest in the UK/EU/EPPO? In the UK and many other European countries, daylilies are an important component of herbaceous amenity plantings in public and private gardens. Puccinia hemerocallidis has the potential to become a common pathogen of daylily in the UK/EU/EPPO. Little is known of the requirements of the pathogen, but it seems capable of infection under a wide range of environmental conditions. Affected plants are not killed, but infection, which causes an unsightly blemish on leaves, diminishes their amenity value and makes the plants unmarketable. Repeated infections result in a decline in the health of plants (Williams-Woodward and Buck, 2001). However, some daylily cultivars are reported to be resistant and the use of this material could limit disease damage (Mueller et al., 2003). There is no information on the effect of the rust on other hosts, but in the USA Patrinia spp are not common as ornamentals and Hosta spp., which have been implicated as uredial/telial hosts (Hiratsuka, 1992), are unaffected (Schubert and Leahy, 2001).
9.  What are the prospects for continued exclusion? In Florida, new infections have been reported to arise in as little as 2-3 days after infection on susceptible varieties of daylily (Schubert and Leahy, 2001). However, in some plants, it has taken as long as 2-3 months before symptoms were seen (T. Schubert, USA, 2001, pers. comm.). Symptoms on the infected daylily first intercepted with rust did not become evident until approximately 2½ months after the plant arrived in the UK (Grant-Downton, UK, 2001, pers. comm.). Some daylily varieties have been reported to be largely unaffected by the rust (Schubert and Leahy, 2001). Florida was the first state in the USA to have recorded the rust problem. Spread to other parts of the USA may have occurred because either (1) plant health inspectors failed to detect light infections, or (2) incubating infections were missed because of the absence of symptoms, or (3) inoculum on plants initiated infections after shipment (T. Schubert, USA, 2001, pers. comm.). Because of the above, it may be difficult for overseas plant health inspectors to certify daylily material exported to the UK/EU/EPPO to be free of the pathogen. The plant intercepted with rust in 2001 was covered by a phytosanitary certificate. Symptoms were not evident on arrival (R. Grant-Downton, UK, 2001, pers. comm.). Any daylilies imported from countries where the rust has been recorded may harbour spores of the pathogen or carry the pathogen as a latent infection. A ban on the importation of daylilies from those countries where the disease has been recorded or the introduction of a requirement that imported daylilies be grown in nurseries where the rust has not been recorded in the last 12 months should assist exclusion.
No information is available on the importation of other hosts of the daylily rust into the
EU/EPPO region so risks are difficult to assess. However, imported species of Patrinia and Hosta should be closely examined for disease symptoms.
The first interception in 2001 was on one of four plants introduced from Florida by a private collector/grower and it is believed that this outbreak has been eradicated. In this instance, the importer was a plant pathologist and, because of his familiarity with plant diseases and knowledge that there was a serious rust of daylilies in the USA, he alerted the UK NPPO to the rust problem. It is possible that infected plants from the same nursery in Florida may have been imported by other individuals within the UK and EU/EPPO region. Therefore, the rust may already be present in Europe.
10.  What are the prospects for eradication? Given the epidemiology of the daylily rust fungus and its ability to survive as a latent infection, eradication may be difficult once the pathogen is introduced. Puccinia hemerocallidis is capable of surviving on daylily (and possibly Hosta spp.) alone; no other host species is required for it to perennate. It spreads by means of wind-blown or water-splashed urediospores and the movement of affected plants. However, if infected plants are detected before spread is possible and there are no other hosts in close vicinity, there is a chance that the fungus could be eradicated.
Spores of the rust fungus released from Patrinia spp. can infect daylily and possibly Hosta spp. in the same way. Again if infected plants are detected before spread, the fungus could be eradicated.
11. How would eradication be achieved? Eradication would be achieved by the destruction of affected plants and by quarantining surrounding daylilies and other hosts, which would need to be cut back and treated with systemic fungicides for an extended period. Propiconazole and azoxystrobin are the fungicides recommended by Schubert and Leahy (2001) and chlorothalonil and azoxystrobin by Buck and Williams-Woodward (2001). In further research, the fungicides that consistently reduced rust development were the broad spectrum protectants chlorothalonil and mancozeb, the sterol-inhibitor triadimefon and the strobilurin azoxystrobin. Myclobutanil allowed the greatest amount of rust development (Buck and Williams-Woodward, 2003). Azoxystrobulin has also been found to have curative activity when applied up to seven days post-inoculation (Mueller et al., 2004). After the treatment of unaffected plants, further inspections at an appropriate interval after application would be needed to confirm eradication.
12.  CSL action recommendations are to:
(1)  Carry out eradication procedures (as detailed above) on affected premises. Destruction of diseased plants and the treatment of associated plants (and possibly any other daylilies and alternate hosts that have been in close contact with any diseased plants) with an effective fungicide with curative activity.
(2)  Initiate surveys of daylily nurseries to determine if the rust is present in other locations in the UK.
(3)  Alert the EU/EPPO authorities to the danger of introducing daylily rust to the region
on material imported from countries with the disease.
(4) Investigate if there are risks posed by the trade of Patrinia and Hosta spp.
13.  References:
Anon. (2002). Daylily rust information page; http://www.ncf.ca/~ah748/rust.html.
Buck, J.W. and Williams-Woodward, J.L. (2001). In vitro fungicide sensitivity and optimum germination temperature of the daylily rust pathogen, Puccinia hemerocallidis. Southern Nursery Association Research Conference 46, 237-239. (http://www.sna.org/research/01proceedings/Section0402.html)
Buck, J.W. and Williams-Woodward, J.L. (2003). The effect of fungicides on urediniospore germination and disease development of daylily rust. Crop Protection 22, 135-140.
EPPO (2002). First report of Puccinia hemerocallidis in Australia. EPPO Reporting Service, 2002/038.
Hernández, J.R., Palm, M.E. and Castlebury, L.A. (2002). Puccinia hemerocallidis, cause of daylily rust, a newly introduced disease in the Americas. Plant Disease 86, 1194-1198.
Hiratsuka, N. (1992) Puccinia hemerocallidis Thuemen 1880. In: The Rust Flora of Japan. Tskuba Shuppankai Ibarki, pp. 710-711.
Mueller, D.S., Jeffers, S.N. and Buck, J.W. (2004). Effect of timing of fungicide applications on development of rusts on daylily, geranium and sunflower. Plant Disease 88, 657-661.
Mueller, D.S., Williams-Woodward, J.L. and Buck, J.W. (2002). Effect of temperature on the daylily rust pathogen. Phytopathology 92 (6 Supplement) S58.
Mueller, D.S., Williams-Woodward, J.L. and Buck, J.W. (2003). Resistance of daylily cultivars to the daylily rust pathogen, Puccinia hemerocallidis. HortScience 38, 1137-1140.
Schubert , T and Leahy, R. (2001). Daylily Rust. Plant Pathology Pest Alert, Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Website;
http://doacs.state.fl.us/~pi/enpp/pathology/daylily-rust.html
Williams-Woodward, J.L. and Buck, J.W. (2001). Daylily rust caused by Puccinia hemerocallidis: a new disease on daylily in the US. Southern Nursery Association Research Conference 46, 234-236.
(http://www.sna.org/research/01proceedings/Section0402.html)
Yoshitaka, O. (2003). Does Puccinia hemerocallidis regularly host-alternate between Hemerocallis and Patrinia plants in Japan? Journal of General Plant Pathology 69, 240-243.

Pest Risk Analyst: David R. Jones

Editor and advice: Claire Sansford

Location: CSL

Date: 17 February 2005

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