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Testing for Fusarium Wilt on Canary Island Date Palm

June 10th, 2015
Padma Sudarshana, Ph.D. - Senior Scientist/Account Manager

Canary Island date palm is a popular ornamental tree of landscapes throughout the world. Fusarium wilt caused by Fusarium oxysporum f. sp. canariensis is the most destructive disease affecting palm trees and reported to be widespread. The Fusarium wilt is a soil borne disease and the pathogen is transmitted mechanically through pruning tools (Feather et al. 1979). Symptoms initiate as one side of leaflets turn yellow to brown and the other side remains green. Extensive discoloration occurs along the petiole and the internal vascular tissue appear as pink to reddish brown (Hodel, 2009). Infected palms die rapidly in hot and dry conditions. Current methods of disease control include prevention of pathogen introduction through infected material and removal of infected trees. In the absence of effective prophylactic measures, screening palm trees, nursery materials and seed lots for the presence of pathogen is essential to limit disease spread (Plyler et al. 1999).

Fusarium wilt diagnosis involves isolation of the fungus from affected plant tissue and culturing on agar media. Because several non-pathogenic Fusarium oxysporum isolates are associated with diseased palms, fungal cultures are isolated and further tested by PCR methods. The culture based method requires 8-10 days to complete. CSP Labs has developed a Bio-PCR method for faster and sensitive method for the detection of F. oxysporum f. sp. canariensis isolates and the test can be completed within 5-7 days. The sample submission forms can be found here.

canariensis

Fusarium oxysporum f. sp. canariensis. Left on TPDA agar. Right on Komada agar.

 

References

  1. Feather, Tolbert V., Howard D. Ohr, and Donald E. Munnecke. “Wilt and dieback of Canary Island palm in California.” California Agriculture 33.7 (1979): 19-20.
  2. Hodel, 2009. Palm diseases in the landscape. UC ANR Publication 74148
  3. Plyler, T. R., Simone, G. W., Fernandez, D., and Kistler, H. C. 1999. Rapid detection of the Fusarium oxysporum lineage containing the Canary Island date palm wilt pathogen. Phytopathology 89:407-413.




Pistachio Bushy Top Syndrome

June 3rd, 2015
Padma Sudarshana, Ph.D. - Senior Scientist/Account Manager

In the recent years, a large number of pistachio trees in California and Arizona orchards have exhibited symptoms such as shortened internodes, twisted roots, stem galls and bushy top. The abnormal growth symptoms were observed with pistachio rootstock, UCB-1 and known to affect 10% to 90% of the trees in an infected orchard (Stamler et al. 2014). A bacterial pathogen, Rhodococcus fascians was identified as the causal organism of the pistachio bushy top syndrome. The California Department of Food and Agriculture (CDFA) assigned a pest rating-C to the pathogen based on the knowledge that R. fascians infections could lower crop yield and result in serious recurring economic losses to the pistachio industry. R. fascians survives as an epiphyte on plant surfaces and favors moist conditions and moderate temperatures. The bacterial transmission occurs primarily through the use of contaminated plant material and can also spread through irrigation water (Chitambar, 2015). R. fascians has a broad host range and survives in soil in the presence of host tissue. The use of disease free plant materials for propagation can be an effective control strategy to limit pathogen spread.

CSP Labs has validated a PCR test for the detection of R. fascians. The instructions for sample submission and forms can be found here.

References:

  1. Stamler, R. A., J. Kilcrease, R. J. Heerama, C. E. Kallsen, and J. J. Randall. 2014. Rhodococcus sp. associated with Pistachio Bushy Top Syndrome in California and Arizona. Plant Disease (accepted for publication).
  2. Chitambar, J. 2015. Rhodococcus fascians. CDFA’s Division of Plant Health’s Pest Ratings and Proposals.