Decline of Casuarina equisetifolia: A Loss to Pacific Island Agroforestry

Decline of Casuarina equisetifolia: A Loss to Pacific Island Agroforestry

Summary

During year three of this project, a one-year extension was granted. This was due to the Research Associate, Dr. Zelalem Mersha, leaving for a new post during year two of the project. Dr. Schlub, the PI, took the lead role in diagnostics. Following authorization, off-island experts were brought to Guam to work on Ironwood Tree Decline (ITWD). Also, experts used their laboratories in the mainland United States to identify pathogens. Major inroads were made in identifying plant pathogens and nematodes associated with ITWD.

Objectives/Performance Targets

Objective 5: Identify a source of seeds from superior ironwood trees that the Guam Department of Agriculture can use in their give-away program (Continued from year two).

Objective 6: Conclusions will be drawn as to the cause or causes for ironwood decline (this objective is for years two and three).

Note: See final paragraph under Accomplishments for a discussion of year three’s original objectives.

Accomplishments/Milestones

1) A source of superior Casuarina equisetifolia seeds from provenance trials at twenty-four locations around the world were sown in air pruning seedling pots and are being maintained in a screenhouse. These trees will be planted as a provenance trial at Bernard Watson’s farm. Also, these trees will be planted in Mr. Watson’s old ironwood tree wind-breaks where the current trees have severely declined or are dead. This will provide information on which trees are most suitable for Guam and which trees are resistant to disease. This is a change from the original proposal. Originally, we were going to plant these trees around Guam to increase the genetic diversity of our ironwood tree. However, after frequent discussions with Phil Cannon, Forest Pathologist, USDA Region 5 and Kevin Eckart, President of Arbor Global, we concluded that a limited area should be used to determine which trees would be most suitable for Guam before doing mass plantings around the island. Bernard Watson has agreed to the use of his land for this purpose.

2) Melodie Putnam, director and chief diagnostician for the Oregon State University Plant Clinic and Senior Plant Pathology Instructor for Oregon State University, came to Guam in January 2011 to offer her expertise in resolving the etiology of ironwood decline. As she has extensive experience as a generalist in Plant Diagnostics, it was felt that she could provide some insight into some of the minor pathogens that had immerged as part of the ironwood decline complex. Samples were collected and photos taken in the field, then analyzed in Dr. Schlub’s laboratory where microscope photos were taken. The minor pathogens included Botryosphaeria (Phomopsis), Fusarium, Pestalotia Diplodia, Phyllostica, Xylaria, Xylella, Phoma, Ralstonia, Nectria, Hypoxylon, Pythium and Phytophthora. With the exception of Ralstonia, all were eliminated as likely contributing factors in decline. With urging of Dr. Putnam, Dr. Anne Alvarez was contacted for assistance in identification of a possible bacterial wilt pathogen. Plans are being made to bring Dr. Alvarez to Guam in 2012 to continue this line of research. See Appendix 1, pages 9-26 for full report.

3) Dr. Marisol Quintanilla, who at the time of her visits to Guam in February and April 2011 held the post of entomologist and nematologist of Northern Mariana College (Saipan) Cooperative Research Extension and Education Service, was brought to Guam to evaluate the possible role of nematodes in ironwood tree decline. In February, root and soil samples were collected by Drs. Quintanilla and Schlub. Samples were processed in Dr. Schlub’s laboratory for the purpose of analysis. Due to the number of samples collected, only some of the samples were analyzed at the time of collection, while others were examined a later. Many plant nematodes were isolated from the root and soil samples; however only two genera were considered as possible contributors to decline: Aphelenchoides and Helicotylenchus. Of these two, Helicotylenchus was the only one that was isolated consistently enough to be remotely implicated in ironwood decline. See Appendix 2, pages 27-30 for full report.

4) A database of sample information collected during Dr. Quintanilla’s and Ms. Putman’s visit, which included sample number, date, GPS location, village and other information, was maintained to allow for cross referencing in reports, photographs and micrographs and to enable return cite visits if necessary. See Appendix 3 pages 31-33.

5) Dr. Catherine Aime of Louisiana State University, a Plant Pathologist specializing in basidiomycetes, continued work on identification of the conks associated with IWTD that we sent her. Previously, she had identified the conks to genus by morphological identification. During 2011 she used nuclear ribosomal (ITS) DNA sequencing extraction to identify a conk as being in the Ganoderma australe species complex. There is no exact match in the world-wide database, so this could be a new species or sub-species of Ganoderma. Ganoderma is the conk most frequently associated with IWTD on Guam.

6) Dr. Schlub and Dr. Merha each gave presentations on ironwood decline at a special session of the 2012 Annual Meeting of the American Phytopathological Society on Tropical Plant Pathology. The published abstracts for the presentations included Decline of Casuarina equisetifolia (ironwood) trees on Guam: symptomatology and explanatory variables, and Decline of Casuarina equisetifolia (ironwood) trees on Guam: Ganoderma and Phellinus. See Appendix 4 pages 34-35 for full abstract and authors.

7) Other Correspondence between Dr. Schlub and scientists on IWTD matters:

Dr. Schlub spent a day with Ann Alverez at the University of Hawaii during the fall of 2011 discussing the possible involvement of Ralstonia solanacearum in ironwood tree decline. Below is a synopsis of discussions.

It is likely some of Guam’s trees have Ralstonia bacterial wilt based on our positive response with Agdia immunostrip and due to the history of wilt on Guam in vegetable crops. However, I have yet to send Dr. Alverez a sample that can be used for confirmation. This may be due to contamination, loss of pathogen during shipping, low titer or poor isolation techniques. It was suggested that bacteria ooze from infected trees be used as inoculum on tomatoes seedlings. Only bacteria from symptomatic tomatoes should be cultured and sent to Ann.

During the course of 2011, Dr. Schlub supported a seminar with Forest Pathologist Phil Cannon of the U.S. Forestry service about forest pathology and a possible ironwood project with U.S. Forestry service.
In May 2011, Phil Cannon presented a seminar at the University of Guam entitled: Puccinia psidii, an emerging plant pathogen in the Pacific. The announcement of the seminar was as follows: Phil Cannon, PhD. Regional Forest Pathologist, from Vallejo, CA will be presenting a half hour seminar on the plant rust Puccinia psidii. First described in 1880s on guava in Brazil, it has since appeared throughout the tropics on a large number of plants in the group Myrtaceae. With its emergence in Hawaii in 2005, it is only a matter of time before it appears in American Samoa, Guam and the Commonwealth of the Northern Mariana Islands. The seminar will be held at UOG in room 202 of the Agriculture Science building on Thursday May 12 at 4:00 PM. Dr. Schlub also presented a seminar on IWTD at this time.

Dr. Schlub recorded the following comments following various conversations with Phil Cannon about ironwood decline.

There is a need for a tri-fold on how to identify and reduce Root and Butt of ironwood on Guam. Such a document could be easy distributed throughout Guam and the region, thereby becoming an effective means of bringing attention to the problem and reducing its impact.
A draft of the document could be sent to Cathie Aime, Scot Nelson, Fred Brooks, Jason Smith and Kevin Eckert for comment. Content would include photos of conks, symptoms and management practices to protect trunks and roots.

Other projects discussed: restoration pruning, tree spacing, prophylactic pruning to protect trees and wind-firming. Points of contact on such of a project would be Ken James of Australia and Ed Gilman at University of Florida.

8) Bibliography:

Mersha, Z., Aime, M. C., Cannon, P., Nandwani, D., Nelson, S., Spaine, P.C., and Schlub, R.L.2011. Decline of Casuarina equisetifolia (ironwood) trees on Guam: Ganoderma and Phellinus. Phytopathology 101:S216.
Schlub, R.L. 2011. Guam’s Dying Gago Gain Worldwide Attention. In: Terral, O. (ed), 2010 Impact Report, Western Pacific Tropical Research Center, University of Guam, pp15-16.

Schlub, R.L., Mersha, Z., Aime, C.M., Badilles, A., Cannon, P.G., Marx, P.G. , McConnell, J., Moore, A., Nandwani, D., Nelson,S.C., Pinyopusarerk, K., Schlub, K.A., Smith, J.A., and Spaine, P.O. 2011. Guam Ironwood (Casuarina equisetifolia) Tree Decline Conference and Follow-up. In: Zhong, C., Pinyopusarerk, K., Kalinganire, A., Franche, C. (eds), Proceedings of the 4th International Casuarina Workshop, Haikou, China 21-25 March 2010, pp239-246.

Schlub, R.L., Moore, A., Marx, B., Schlub, K., Kennaway, L., Quintanilla, M., Putnam, M., Mersha, Z., 2011. Decline of Casuarina equisetifolia (ironwood) trees on Guam: Symptomatology and explanatory variables. Phytopathology 101:S216.

9) The following is a list of the original year three objectives, followed by a short discussion of the progress during the (current) no cost extension year.

Objective 6: Based an analysis of the data collected in Objectives 1-3, a conclusion will be drawn as to the cause or causes for ironwood decline.

Objective 7: Drawing from the results of objective 6 and the knowledge and expertise of others, the Ironwood Tree Decline Committee will develop management strategies for ironwood decline and host a three half-day ironwood tree workshops: one for government agency employees and two for farmers and the general public. Product: An manual on IWTD, Ironwood tree care and general tree care.

There has been a lot of progress made on objective six as reported in the second and third (this report) years annual reports. Work continues on this objective in this extension year.

Object 7 was completed in January 2012 and will be reported on at length in the final report. We expanded this objective to three full day workshops and a half day workshop. A draft of the manual has been completed and was available for use by participants at the workshops. The finished product will accompany the final report package.

• Appendix

Impacts and Contributions/Outcomes

1) Outreach activities for the general public included presentations on the importance of the ironwood tree to the island’s ecology and agriculture, how to care for ironwood trees and how to identify and reduce the impact of Ironwood Tree Decline (IWTD). Activities included instruction of Cooperative Extension field agents and University of Guam Agriculture majors conducted by Dr. Schlub and Ms. Melody Putman of Oregon State University (Picture 1). Interactive displays were set up at the University of Guam’s Charter Day and at the Environmental Protection Agency’s Earth Day (Picture 2 and 3). As a result of these activities, hundreds of visitors, made up of students, teachers, farmers and members of the general public, were informed about ironwood tree decline and ironwood tree care. The number of landowners and managers trained to develop Stewardship Plans during these events were approximately 50. The number of direct contacts which increased awareness of benefits and opportunities during these events was approximately 930.

2) Outreach activities for the scientific community included two presentations at the Forest Pathology and Tropical Plant Pathology special session of the 2012 Annual Meeting of the American Phytopathological Society and two accompanying abstracts, which are presented under Accomplishments.

• Picture 1: Melodi Putman (standing with arms folded) observes CES field agents
• Picture 2. Dr. Robert Schlub discusses IWTD with visiting students at the
• Picture 3. Guam Lieutenant Governor Raymond Tenorio (left) visiting

Collaborators: