Witches Broom
A summary from iSpot (migrated 2019-08-01):
Witches Broom in Proteaceae
16 March 2015 - 2:12PM
By Tony Rebelo
A project to highlight the Witches Broom Phytoplasma on primarily Proteaceae.
480 READS R
Comments
Witches Broom only
4 May 2015 - 10:43AM Tony Rebelo
One of the early goals of this project - to find out why Other Organisms were not getting a Likely ID is now here: http://www.ispotnature.org/projects/help-with-ids--southern-african-community--other-organisms
This thus focuses on Witches Broom only
The southern African community has migrated to iNaturalist at www.inaturalist.org with all its data in early 2018. Beware that southern African data and identifications on this site are out of date and no longer updated.
Presently including nonsense
4 May 2015 - 11:34PM Riaan Stals
You will have to specify 'Likely ID only', please.
ex BEETLEDUDE
Thanks for that
5 May 2015 - 12:12AM Tony Rebelo
Have been careless with reconstituting this, and I did forget about this quirk. Thanks for highlighting it.
Heaven help beginners!!
Interactions
5 May 2015 - 12:21AM Tony Rebelo
Now this is a project that would really benefit from an "interactions filter"
From the Protea Atlas Project:
5 May 2015 - 12:13AM Tony Rebelo
http://www.proteaatlas.org.za/witches.htm :
Thank you to everyone who has sent in data with Witches Broom to date. This list is quite impressive: 41 protea species are afflicted with this disease, plus a number of other species. If you see witches broom, and especially on a species not listed below, please remember to note it in your additional remarks box. Protea Atlas Logo
Witches broom and similar-looking afflictions:
Au umbellata
Ha sericea
Ld procerum, salignum, stellare, teretifolium
Ls arenarium, conocarpodendron, hypophyllocarpo-dendron, parile, praemorsum, tomentosum
Pr angustata, burchellii, caffra, coronata, compacta, cynaroides, denticulata, eximia, glabra, humiflora, laevis, lanceolata, laurifolia, lepidocarpodendron, longifolia, magnifica, mundii, neriifolia, nitida, obtusifolia, repens, scabra, speciosa, stokoei, scolymocephala, sulphurea, tenax
Se phylicoides
Ve obtusata albomontana.
Note that the Bearded and Spoon-bract Sugarbushes and Sandveld Pincushions seem to feature most prominently. Hybrids have not been listed. More data would be appreciated!
Witches Broom - A Conebush Disaster
5 May 2015 - 12:17AM Tony Rebelo
Witches Broom - A Conebush Disaster
The Agricultural Research Council Fynbos has suspended the sale of all Conebush cuttings to the cut flower trade industry because of two new diseases. These are (from SAPPEX News 104: 6-7):
Yellow Leaf Blotch.
A yellow discoloring on veins of young leaves that matures into little rectangular lesions, thought to be caused by a virus. At first it can be confused with a nutrient deficiency. It seems to spread rapidly even on sterilized pruning shears. Any plants (especially the cultivars Rosette and Safari Sunset) brought from Elsenberg during 1998-9 may be infected. A mild form was seen on Pr susannae at Elsenberg as well.
Witches’ Broom
When atlassers recorded Witches’ Broom in our survey of Witches’ Broom for Rose Newton (PAN 31.11 - are you still remembering to record this when you see it?) on Conebushes and other plants it was poo-pooed as spurious – "Witches’ Broom only occurs on proteas". Now it is a serious problem on Conebushes. Initial tests suggest that the symptoms are associated with a mite similar to the Protea Witches’ Broom Mite Aceria proteae, but that (as atlassers noted!)* the symptoms are not full broom, but more a miniaturization or bonsai effect. It is now a major problem on most cultivars - "in almost all Jubilee Crown, Pisa and Chameleon fields and also in Inca Gold" (bold emphasis inserted). The problem has also surfaced in the Northern Hemisphere. It seems to be spread by both aphids and pruning shears.
We hope that this is a temporary inconvenience to the industry – more importantly to the development of new cultivars. It will certainly mean that many growers will have to prematurely replace their orchards. But what will they be replaced with? Elsenberg is trying to determine the causative agents, although I find the attitude - that "… the search for a cure cannot begin" … "until it is known what the cause is …" - to be both short sighted and ridiculous. Experimenting with acaricides and pruning hygiene may well yield a cure to the problem before the causative agents are discovered. Given that all Conebush distribution has ceased, with growers potentially losing large orchards, surely the expense is justified? Tony
*Atlassers even recorded Witches Broom on a Needlebush. A 4m tall Ha sericea plant near Paarl had half the bush stunted with 3mm-long needles in dense, broom-like growths. Unfortunately, this plant was cleared for a fruit orchard in 1998. Rose could not find any mites in the broom at the time.
http://www.proteaatlas.org.za/witches2.htm - PAN46 March 2000
Catch that Witch!
5 May 2015 - 12:20AM Tony Rebelo
Rosemary Newton Botany Dept UCT
Witches’ broom is a disease that occurs on many members of the genus Protea. The symptoms of the disease are a characteristic thick, bushy growth, consisting of poorly developed shoots with thin stems and minute, often distorted leaves. The "broom" is produced from normally dormant floral or axial buds. Single branches on plants or whole plants can be affected. The growth is formed from excessive bud proliferation. Diseased plants can only be identified by symptom observation, and the physical change of the plant is irreversible.
Infection may take place from the early seedling stage, and thereafter can occur at any time during the life of the mature plant. The cause, or agent, of the disease has not yet been identified, but is thought to be a microscopic mycoplasma-like organism, which remains in the plant throughout its life. Mycoplasmas are bacteria that do not possess cell walls, and are mostly pathogenic in animals and plants. A toxin from these mycoplasmas is believed to stimulate the bud to divide and subdivide to form the witches’ broom growth.
The mode of transmission of the disease to other parts of the plant and to other plants is unknown. However it has been suggested that, due to close association, transmission may be with an eriophyid mite (Aceria proteae), that is believed to show specificity for host plants. The mites are colourless, banana-shaped and microscopically small. These mites have been found to occur under bracts in dormant leaf buds, in flower buds (in unopened flowerheads) and in witches’ brooms. Other members of the Eriophyidae are known vectors for plant pathogens. The mite itself is probably dispersed by wind, man, and possibly birds.
Control of the disease in flower farms is most effective by prevention, by ensuring diseased plants are not sold from nurseries, and by mite control, through regular miticide application. Heavily infested adults and diseased seedlings must be destroyed as it is impossible to restore them to economic production. Light infestations on mature plants can be pruned. All infested material should be destroyed by burning, to stop further spread of the disease.
There is still a great deal about witches’ broom that remains a mystery. I have been struck by the patchiness of the disease in nature. Sometimes every plant is infected, sometimes only the rare few. Some Protea species carry heavy loads of the broom, others seem quite unaffected. Even within a plant, it is far from clear how the disease spreads. For example, do infected individuals produce infected seeds?
As part of an honours project, I am trying to determine the extent of the disease and patterns of infection and spread. I am hoping that results may prove useful to Protea growers in understanding the disease, and controlling it more effectively. This is where the assistance of avid amateurs will be invaluable. I am compiling a list of all the species infected by witches’ broom. Does the disease occur on genera other than Protea? Is it confined to only some sections of Protea? Have atlassers observed any interesting patterns which might help explain distribution or transmission of the disease? I’d be very grateful for comments or observations from atlassers, especially lists of species known to have witches’ broom, and their localities.
Please report all sightings of the "witch" to Rosemary Newton, Botany Dept, University of Cape Town, Rondebosch, 7700: FAX (021) 650-4041, or e-mail: RNEWTON@ BOTZOO.UCT.AC.ZA.
Useful References
R. Dorrington 1988. Witches’ broom disease of Protea cynaroides. SAPPEX News 59: 20.
L. Forsberg 1993. Protea diseases and their control. The Queensland Agricultural Journal Reprint: 1-13.
A.C. Myburgh & D. Rust 1971. Witches broom of proteas. Information Bulletin 34. Fruit and Food Technology Research Institute, Stellenbosch. 3pp.
R.J. Rust & A.C. Myburgh 1976. Heksebesem by proteas. Veld & Flora 62: 21-22.
S.L. van Broembsen 1989. Handbook of Diseases of Cut-flower Proteas. Internatnl Protea Association, Victoria.
If atlassers record the presence of witches' broom on the SRS in the additional remarks, we will forward the data to Rosemary. Please note: this project will have to be completed sometime around September, so exciting data are really required by June at the latest. Exciting data include witches' broom on genera other than the Sugarbushes. Less exciting, but just as important, are where witches' broom occurs on the known hosts - these data are of interest independent of Rosemary's work - so please let us have the data anytime.
We have unconfirmed reports of witches' broom-type infections on Ls tomentosum and Ld salignum. We will process existing data for Rosemary and report progress in the next newsletters.
Tony Rebelo
http://www.proteaatlas.org.za/p30witch.htm PAN30 March 1996
The links above are defunct. Please post any new observations here
