Ecology of Guam’s Casuarina equisetifolia and research into its decline

Robert L. Schlub; Caleb M. Ayin; Anne M. Alvarez; Sujan Paudel; Mohammad Arif; Brian D. Marx; Claudia Husseneder; Karl A. Schlub; Marisol Quintanilla; Ned B. Klopfenstein; Lisa F. Kennaway; Yong Zhang; Chonglu Zhong; Abel Nicodemus

Treesearch

Ecology of Guam’s Casuarina equisetifolia and research into its decline

Informally Refereed

Authors:

Robert L. Schlub, Caleb M. Ayin, Anne M. Alvarez, Sujan Paudel, Mohammad Arif, Brian D. Marx, Claudia Husseneder, Karl A. Schlub, Marisol Quintanilla, Ned B. Klopfenstein, Lisa F. Kennaway, Yong Zhang, Chonglu Zhong, Abel Nicodemus

Year:

2020

Type:

Miscellaneous

Station:

Rocky Mountain Research Station

Source:

In: Haruthaithanasan, M.; Pinyopusarerk, K.; Nicodermus, A; Bush, D.; Thomson, L. eds. Proceedings of the Sixth International Casuarina Workshop: Casuarinas for green economy and environmental sustainability; Krabi, Thailand; 21-25 October 2019. IUFRO Working Party 2.08.02; IUFRO Task Force Forest Biomass Network. Bangkok, Thailand: Kasetsart Agriculture And Agro-Industrial Product Improvement Institute. p. 237-245.

Download (PDF 314 KB)

Download (PDF 314 KB): https://research.fs.usda.gov/download/treesearch/61278.pdf

Abstract

On Guam, the estimated lifespan of Casuarina equisetifolia subsp. equisetifolia is 35 to 90 years and trees may reach a height of 24 m and a diameter at breast height of 92 cm. The majority of its trees are monecious. In 2002, it was noticed that many trees were in a slow decline and when felled, droplets often formed on their fresh stumps. In 2009, this condition was coined ironwood tree decline (IWTD). The droplets which consisted of various mixtures of plant exudates and bacterial ooze were found to contain Ralstonia solanacearum and various wetwood bacteria. Reported in 2015 and confirmed in 2020, Guam’s R. solanacearum strains are of the phylotype 1 (Asia). Cross-sections of IWTD trees from Guam are very similar in appearance with those of bacterial wilt from China. In 2012, a project was initiated to diversify the gene pool and identify resistance of C. equisetifolia in Guam trees. Using the 1991-1993 international provenance trials of C. equisetifolia, 11 geographically paired seedlots were planted at a farm where IWTD was present. Over the succeeding years, none of these trees have developed IWTD nor tested positive for R. solanacearum. Over the years, the following pests were investigated and ruled out as contributors to IWTD: Protaetia orientalis, Protaetia pryeri, Selitrichodes casuarinae, Helicotylenchus sp. and Phellinus sp. Between 2010-2019, data analyses identified three prominent variables as predictors of IWTD: bacterial wilt pathogen R. solanacearum, butt and root rot fungus Ganoderma australe and termites. In 2019, Nasutitermes takasagoensis complex was found to be the dominant termite species infesting Guam’s C. equisetifolia.

Keywords

Casuarina equisetifolia, Ralstonia solanacearum, Ganoderma australe, wetwood, ironwood tree decline on Guam, bacterial wilt China, bacterial wilt India

Citation

Schlub, Robert L.; Ayin, Caleb M.; Alvarez, Anne M.; Paudel, Sujan; Arif, Mohammad; Marx, Brian D.; Husseneder, Claudia; Schlub, Karl A.; Quintanilla, Marisol; Klopfenstein, Ned B.; Kennaway, Lisa F.; Zhang, Yong; Zhong, Chonglu; Nicodemus, Abel. 2020. Ecology of Guam’s Casuarina equisetifolia and research into its decline. in: Haruthaithanasan, M.; Pinyopusarerk, K.; Nicodermus, A; Bush, D.; Thomson, L. eds. Proceedings of the Sixth International Casuarina Workshop: Casuarinas for green economy and environmental sustainability; Krabi, Thailand; 21-25 October 2019. IUFRO Working Party 2.08.02; IUFRO Task Force Forest Biomass Network. Bangkok, Thailand: Kasetsart Agriculture And Agro-Industrial Product Improvement Institute. p. 237-245.