Kweilingia divina | Pest Rating Proposals and Final Ratings

California Pest Rating for

Kweilingia divina (Syd.) Buriticá 1998

Pest Rating: A

PEST RATING PROFILE

Initiating Event:

In December 2014, Kweilingia divina was detected in a quarantine interception of bamboo leaves showing symptoms of rust, imported from Florida to California. The detection was made by Contra Costa Agricultural Commissioner’s office inspector and the associated pathogen was identified by Suzanne Latham, CDFA plant pathologist. This rust fungus had also been intercepted in 2006 by Los Angeles County in a similar shipment of bamboo from Hawaii. All infected plants were destroyed. The risk of introduction and establishment of Kweilingia divina in California is evaluated here and a permanent rating is proposed.

History & Status:

Background: The bamboo rust fungal pathogen, Kweilingia divina was originally ascribed as the type species of the genus Dasturella (D. divina) which was detected in infected bamboo leaves (Bambusa sp.) in 1943 (Mundkur & Kheswalla, 1943). However, in 1998, Dasterulla divina was renamed Kweilingia divina.

Kweilingia divina requires two different kinds of hosts to complete its life cycle (heteroecious), producing two types of specialized spores on each host, namely urediniospores and teliospores on bamboo and spermatia (pycniospores) and aeciospores on its alternate host, Catunaregam spinosa (mountain pomegranata). The pycnial and aecial state are not known in the New World (Farr & Rossman, 2015).

Hosts: Several species of bamboo including, Bambusa balcooa, B. bambos, B. domestica, B. multiplex, B. mutabilis, B. oldhami, B. polymorpha, B. tulda, B. shimadai, B. tuldoides, B. vulgaris, Dendrocalamus brandisii, D. hamiltonii, D. latiflorus, D. longispathus, D. strictus, Ischurochloa stenostachya, Ochlandra scriptoria, O. travancorica, Oxtenanthera sp.,O. abyssinica, O. nigrociliata, Phyllostachys bambusoides,Pleioblastus sp., Pseudoxytenanthera ritcheyi, Pseudosasa japonica var. usawai, P. usawai, Shibataea kumasaca, Thyrsostachys oliveri, T. sianensis, and the alternate, non-bamboo host Catunaregam spinosa (Blomquist et al., 2009; Cummins, 1971; Nelson & Goo, 2011; Farr & Rossman, 2015).

Symptoms: On bamboo, initial symptoms of infection are the presence of water-soaked, pinhead-sized flecks on the lower surface of leaves. Soon yellowish-orange to brown, elongate, interveinal, linearly aligned fruiting structures (uredinia) develop and produce urediniospores. On the corresponding side of the upper leaf surface, grayish-brown to dark brown lesions with yellowish halos for along the parallel veins. Numerous lesions may develop on a leaf surface or coalesce to form larger areas of tan-colored necrotic blight. Over time, brownish black linear structures (telia) develop within the lesions on the lower leaf, either inside old, degenerating uredinia or separately. Severely infected leaves defoliate prematurely (Nelson & Goo, 2011). The alternate host, Catunaregam spinosa is not present in California but is native to tropical Southeast Asia and tropical Africa.

Damage Potential: Bamboo is not a main cultivated crop in California. However, bamboo plants are grown and sold mainly as nursery ornamentals and commercial plantings in private residences, public parks, amusement parks, and other environments. The bamboo rust disease is a threat to these limited yet economically important regions where bamboo is grown in California. Rusted bamboo leaves are not only aesthetically unsightly but also negatively impact plant growth. Severe infestations of bamboo rust can result in defoliation and reduction in plant growth, vigor and stand. Once established in California, containment and management of the rust pathogen will be difficult as infected leaves produce masses of air-borne spores enabling long-range spread and infection.

Transmission: The pathogen is spread from plant to plant mainly by windblown spores. Urediniospores can be transported over several hundred kilometers by strong winds and washed down by rain to available hosts. Insects, animals, humans, and rain may also aid in spreading spores to non-infected plants. Infected nursery plants also aid in introducing and spreading the pathogen.

Worldwide Distribution: Asia: India, China, Hong Kong, Japan, Pakistan, Taiwan, Malaysia; Africa: Cote d’Ivoire, Ghana, Nigeria, North America: Mexico, USA; Oceania: Australia, New Calendonia, Samoa; Caribbean Islands: Cuba, Dominican Republic, Jamaica, Puerto Rico, Trinidad and Tobago, West Indies, Virgin Islands; Central America: Costa Rica; South America: Brazil, Guyana, Colombia, French Guiana (Farr & Rossman, 2015).

In the USA it has been reported from the Hawaiian Islands (Oahu, Hawaii, Kauai, and Maui). The detections in California resulted in the eradication of the disease (Blomquist et al., 2009; Nelson & Goo, 2011).

Official Control: None reported.

California Distribution: Bamboo rust pathogen, Kweilingia divina, is not established in California. All 2006 and 2014 intercepted shipments of infected bamboo plants were destroyed (see ‘Initiating Event’).

California Interceptions: Kweilingia divina was intercepted in Los Angeles in 2006 and in Contra Costa County in 2014.

The risk Kweilingia divina would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.
– Medium (2) may be able to establish in a larger but limited part of California.
– High (3) likely to establish a widespread distribution in California.

Risk is High (3) – Kweilingia divina is able to establish a widespread distribution in California wherever bamboo is grown.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

– Low (1) has a very limited host range.
– Medium (2) has a moderate host range.
– High (3) has a wide host range.

Risk is Low (1) – The host range of Kweilingia divina is mainly limited to several species of bamboo. The alternate host does not exist in California.

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– Low (1) does not have high reproductive or dispersal potential.
– Medium (2) has either high reproductive or dispersal potential.
– High (3) has both high reproduction and dispersal potential.

Risk is High (3) – The infective spores of Kweilingia divina namely, urediniospores, are produced in abundance and are spread to healthy plants mainly by wind. Insects, animals, humans, rain, and infected nursery plants also aid in its spread.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

A. The pest could lower crop yield.
B. The pest could lower crop value (includes increasing crop production costs).
C. The pest could trigger the loss of markets (includes quarantines).
D. The pest could negatively change normal cultural practices.
E. The pest can vector, or is vectored, by another pestiferous organism.
F. The organism is injurious or poisonous to agriculturally important animals.
G. The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.
– Medium (2) causes 2 of these impacts.
– High (3) causes 3 or more of these impacts.

Risk is High (3) – Severe infestations of the bamboo rust pathogen could result in defoliation and reduction of plant growth, vigor and stand, and loss of markets. Nursery plantings are at risk being significantly impacted by the introduction of this pathogen. Without eradicative action subsequent to detection of bamboo rust-infected plants within greenhouse environments, there is the risk of spread to the outside environment. The spread of the rust pathogen would be difficult to manage due to its effective means of windblown transmission.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.
B. The pest could directly affect threatened or endangered species.
C. The pest could impact threatened or endangered species by disrupting critical habitats.
D. The pest could trigger additional official or private treatment programs.
E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.
– Medium (2) causes one of the above to occur.
– High (3) causes two or more of the above to occur.

Risk is High (3) – Outbreaks of the disease could have significant impact on established bamboo ecosystems. Commercial bamboo plantings in public parks, resorts and plantings in private residences may be impacted by the bamboo rust pathogen subsequently triggering additional treatment programs.

Consequences of Introduction to California for Kweilingia divina

Add up the total score and include it here. (Score)

-Low = 5-8 points
-Medium = 9-12 points
-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Kweilingia divina to California = (13).

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

-Not established (0) Pest never detected in California, or known only from incursions.
-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation: Kweilingia divina is not established in California (0).

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score: Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 13

Uncertainty:

Future detection surveys for Kweilingia divina in nurseries and established bamboo groves are needed to gain further information of the probable introduction, establishment and distribution of this pathogen in California. This information could alter the proposed rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Kweilingia divina is A.

References:

Blomquist, C. L., J. M. McKemy, M. C. Aime, R. W. Orsburn and S. A. Kinnee. 2009. First report of bamboo rust caused by Kweilingia divina on Bambusa domestica in Los Angeles County, California. Plant Disease 93: 201. http://dx.doi.org/10.1094/PDIS-93-2-0201A

Cummins, G. B. 1971. The rust fungi of cereals, grasses and bamboos. Springer-Verlag New York Inc. 570 p.

Farr, D. R., and A. Y. Rossman. 2015. Fungal databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved March 18, 2015, from http://nt.ars-grin.gov/fungaldatabases/

Johnson, G. I. 1985. Rust (Dasturella divina) of Bambusa spp. in Australia. Australasian Plant Pathology 14:54-55.

Mundkur, B.B., and K. F. Kheswalla. 1943. Dasturella: A New Genus of Uredinales. Mycologia 35:201–206.

Nelson, S., and M. Goo. 2011. Kweilingia rust of bamboo in Hawaii. College of Tropical Agriculture and Human Resources, University of Hawaii at Mānoa. Plant Disease PD-74.

Responsible Party:

Dr. John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.