Publications (pathogens of plants of Hawaii)

Pathogens of plants of Hawaii
PUBLICATIONS

[ Home ] [ Hosts ] [ Pathogens ] [ Publications ] [ Images ] [ Database ]

Gardner, D. E. . Unpublished: Transmission and diagnostic studies of Dodonaea yellows Unpublished

ABSTRACT
In addition to our published reports of Dodonaea yellows, the following work was done with Dodonaea yellows. I had not found any reference to this disease as such in the literature. (As mentioned above, the only report of interest was the reference to D. viscosa as a host of sandalwood spike in India. Since, as an indigenous plant D. viscosa is widely distributed throughout the Pacific, the Indian region, and occurs from Mexico to Venezuela, I attempted to determine if perhaps unpublished observations of symptoms similar to those of Dodonaea yellows in Hawaii had been made. Prior to the availability of the World Wide Web, I mailed color photos of the symptoms to several researchers in countries where Dodonaea was known to occur. I received a negative reply in each case, suggesting that Dodonaea yellows was unique to Hawaii. Even researchers in India stated that sandalwood spike did not entirely resemble the disease on Dodonaea. As a follow-up to this project, similar pictures could be sent out via the Internet for a much wider coverage. (In fact, my website, available for several years, does include these photos but even with this I have not received any response that the disease occurs elsewhere. Other "yellows" diseases have been diagnosed by treating symptomatic plants with oxytetracycline type antibiotics, which result in a remission of symptoms. My assistants and I used hypodermic syringes and "Moget Tree Injectors" (a commercial device developed for injection of liquid fertilizers under pressure) to inject various concentrations of this class of antibiotics into diseased trees in the field. Grafting experiments between diseased and healthy tissue were also attempted in an effort to determine if the disease could be graft- transmitted. Furthermore, phytoplasmas, the cause of "yellows" diseases, have been shown to be heat sensitive. Small symptomatic plants in the field were "tented" and exposed to elevated air temperatures on a periodic basis provided by an electric space heater powered by a portable generator. However, no positive results were obtained by these diagnostic methods, so these attempts were not formally published. The mechanism of transmission of Dodonaea yellows remains unknown, although yellows-type phytoplasmas are typically transmitted by leafhoppers. In characterizing the disease in Hawaii, it would be interesting to know whether native or nonnative insects may be the vectors, and how host-specific the vector(s) are. Clifton Davis, DOA biocontrol entomologist (now deceased), conducted a survey of insects found on Dodonaea in HAVO. His unpublished list is included with this report. Efforts to determine which of these species may be vectors for Dodonaea yellows were briefly undertaken by research assistant Rob Anderson by netting insects on diseased plants and caging them on healthy plants. Time and work requirement restrictions didn't allow these efforts to continue long enough to be definitive, however. I discovered an eriophyid mite associated with Dodonaea and wondered whether the mite might be a (or the) vector of Dodonaea yellows. This possibility was supported by the work of Dr. George Oldfield, an expert on eriophyid mites of the University of California, Riverside. Dr. Oldfield collaborated in our study and traveled to Hawaii to observe Dodonaea yellows disease in the field. Working with a binocular microscope, I transferred numerous mites from symptomatic tissue to a number of healthy plants grown from seed in the greenhouse. However, none of the healthy plants developed disease symptoms. The possibility exits that the disease is transmitted by the mite, but that the mite isn't very proficient at transmission. More of this work, with a wider sampling of healthy test plants, would be desirable to more conclusively eliminate the mite as a vector of the disease. (Refer to the published reports for an account of our attempts to characterize this disease as being caused by a phytoplasma. A number of questions still remain concerning this disease. Borth completed a dissertation study on the disease sponsored by my program. He provided evidence that both a virus [as indicated by the presence of double-stranded RNA] and a phytoplasma were associated with it. The role of each of these entities in producing the symptoms needs to be clarified. As mentioned above, the means of spread, whether by native or nonnative vectors or through other means needs to be determined, and the origins of the disease itself, whether native to Hawaii or introduced from elsewhere, need to be established). I presented a description of Dodonaea yellows as a new disease at the 1986 Pacific Division meeting of the American Phytopathological Society in Sacramento, California. Dr. Edwin Florance of Lewis & Clark College in Oregon expressed interest in collaborating with me in determining the etiology of the disease. He was experienced in detection of phytoferritin associated with phytoplasma-caused diseases and suggested that phytoferritin might be found in Dodonaea yellows-diseased plants. Phytoferritin which appears as a dense, black, granular substance in transmission electron micrographs of diseased plant tissue and is diagnostic of phytoplasma infection. Phytoferritin was detected in diseased Dodonaea tissue, but the observations were not sufficiently consistent to warrant publication.

FULL TEXT
Full text not available for this publication.

HOSTS
Dodonaea sp. - 'a'ali'i

PATHOGENS
No pathogen information available for this publication.

RELEVANT TO BIOCONTROL
No.

KEY WORDS
Yellows disease, Dodonaea.

IMAGES

	02_028 - Dodonaea viscosa yellowing PATHOGEN: Aspergillus melleus
	02_029 - Dodonaea viscosa yellowing PATHOGEN: Aspergillus melleus
	27_038 - heat treatment of diseased Dodonaea at powerline road PATHOGEN: Aspergillus melleus
	27_039 - heat treatment of diseased Dodonaea at powerline road PATHOGEN: Aspergillus melleus
	27_040 - diseased Dodonaea immediately following heat treatment PATHOGEN: Aspergillus melleus

[ PIERC home ] [ PBIN home ] [ HEAR home ]

Comments? Questions? e-mail webmaster@hear.org. This template was created on 02 June 2004 by Starr, and was last updated on 10 August 2005 by PT.