The following statement was made in this thread on April 29, 2009: "It has been demonstrated by natural root grafting at UC Davis, but then only on rootstock plants just a few inches from each other, in the nursery row, and then only on mutiflora." In 2007 Golino et.al. at U.C. Davis published a paper on this subject. The abstract is at: http://www.actahort.org/books/751/751_26.htm In the full paper, the following is stated (page 29-30): "Field Spread in Scion Cultivars To test further for the occurrence of virus spread trials were conducted on over 300 plants each of three scion cultivars, Double Delight, Iceberg, and Queen Elizabeth. Rooted cuttings were planted approximately 30 cm apart in rows in the field, grown for one year and alternate plants were graft-inoculated as described above with one of three virus accessions: 1) ROS98.36, 2) ROS98.27, and 3) ROS70.7, which were 1) a source of PNRSV that caused bright yellow chlorosis in the spring; 2) a source of ApMV, and 3) a source of a naturally-occurring mixed infection of ApMV and PNRSV, respectively. Plants were pruned yearly using shears that were cleaned between each plant by dipping in 10% bleach solution. Bushes were observed for symptoms periodically and ELISA tested for PNRSV and ApMV in the spring for two years. All non-inoculated plants that tested positive were re-sampled and tested to confirm the result." In the conclusion section (page 221) the following was stated: "In scion varieties, transmission rates two years postinoculation ranged from 0 to 25% depending on virus and cultivar. Queen Elizabeth had the lowest percent infection of all the varieties at an average 5% for all three viruses; Iceberg had the highest for a scion cultivar at 13% average for the viruses (Table 4). These differences correlate with the cultivars relative root vigor. It is possible that a larger, more vigorous root system would increase the chance of forming a root graft with an adjacent plant. R. multiflora has a more vigorous root system than all three scion cultivars tested and within the scions, Iceberg is more vigorous than Queen Elizabeth and Double Delight." -------------------------------- I do not understand why someone would make the April 29 statement. Especially since on April 30, 2009 the same writer states: "If one actually looks up Golino's paper in Acta Horticulturae......." ----------------------------------- Please also note that not all types of mechanical transmission were ruled out in the 2007 paper since the observed rate of spread was higher in the unpruned bushes than in the pruned bushes. In another PNRSV infected plant, hops, this is attributed, in part, to the branches of neighboring plants rubbing against each other. Golino et.al. acknowledge this as they state (page 220-221): "The possibility remains that spread occurred by mechanical transmission due to contact between the leaves of the closely spaced plants and experiments are underway to test that putative mechanism of spread."

To address a few of the points and questions, I don't have a lot of answers, but will try. I have owned this clump for almost 15 years, long before I had ever heard of HVX. Then I got a copy of the Hosta Handbook, and Zilis made it clear that it was a genetic anomaly, and not a virus, so of course I felt relieved. He again mentions the same thing in the Hostapedia. If this hosta has been run through extensive virus indexing other than HVX then I am not aware of it. I just had an opportunity to get it tested, and I jumped at the chance. I agree with Chris that it would be very interesting to test other clumps of Cynthia to see if the results could be duplicated. Frankly I am skeptical as to whether the CMV is causing the variegation pattern in this plant. By the 4th of July this plant will be all green and not show the color again till next spring. I have never seen nor heard of this look spreading to surrounding plants, and this is the first mottled plant I have submitted for extensive testing. I have seen thrips in hostas before, and they can be a vector for some viruses. I have never personally observed aphids on hosta, but I wouldn't entirely rule it out. Heck, I have seen bagworms attached to hosta, so who knows. By the way, not all aphids can be vectors of viruses. There are many different species of aphids, and only some act as vectors. I have seen wooly leafhoppers on hosta flower scapes before, but I have no idea whether they can vector any diseases. While there are a number of other viruses that can infect hostas, I would never minimize the dangers of HVX. It is still a serious problem and is not going away. In fact, if not for the efforts of Chis at Hallson Gardens, it would be much, much worse. Chris has done a great service for the hosta world by spreading the word, and encouraging people to fight back against the the suppliers of diseased plants. For that I applaud him.

I am interested in what is the natural spread of rose viruses. In designing any experiment one normally calculates the number of samples required to obtain a result that has a 95% confidence level. I think the results of this type of calculation for rose virus spread are interesting. If the natural spread in a field is 1% a year and one checked the field at the end of one year, one would have to examine 2377 plants to be able to report the results as having a 95% confidence level (1.0 +/- 0.4)%. If the natural spread in a field is 4% a year, and one checked the field at the end of one year; one would have to examine 9220 plants to be able to report the results as having a 95% confidence level (4.0 +/- 0.4)%. To be able to report a (4 +/- 1)% spread, the number of plants should be 1475. To be able to report a (4 +/- 2)% spread number, one would need to examine 369 plants. To be able to report a (4 +/- 3)% spread number, one would need to examine 164 plants. The number of plants required for a quantitative study are probably larger than what most researchers would want to undertake. Another approach is a qualitative study to see if the spread is non zero. If designed correctly, positive results of such a study would have a definite meaning but negative results would not. An example of such a study appears to be the published paper by R. H. Converse and A. B. Bartlett, Plant Disease Reporter, volumn 63, pages 441-444, (1979). They studied 21 wild rose plants from 17 Oregon, U.S.A. locations. 5 plants out of the 20 that were tested by agar-gel diffusion (1 plant was not tested) were found to have tobacco streak virus. The positive testing plants came from 4 of the 17 sites (2 positive out of 2 tested from one site; 1 out of 1 tested from another site; 1 out of 3 from another; and 1 out of 1 from another). (The wild rose was not identified in the paper, I suspect that it was R. Setigera.) Here is a link that might be useful: Link to do your own calculations

Has it been found in the U.S.? Many/most U.S. gardeners see a virused rose and call it rose mosaic virus. The term Rose Mosaic Virus is not an actual virus name. It is a group name for viruses that give mosaic symptoms on roses. To determine which virus is giving the observed symptoms, the diseased rose must be tested. "Title: Roses: virus and virus-like diseases. Author: Lisa-V Published in: Colture-Protette. 1998, 27: 5 Supplement, 35-38; 14 ref. Language of article: Italian Abstract: "Notes are given on the viruses and virus-like diseases that are known to affect roses around the world. The most common and widespread virus disease is rose mosaic, associated especially with prunus necrotic ringspot ilarvirus (PNRSV), apple mosaic ilarvirus (ApMV), arabis mosaic nepovirus (ArMV) and strawberry latent ringspot nepovirus (SLRV), but also with tobacco ringspot nepovirus, tobacco streak ilarvius and tomato ringspot nepovirus. Tobacco mosaic tobamovirus and an unidentified closterovirus are found sporadically. The virus-like diseases of unknown aetiology include rose ring pattern, rose flower break, rose streak, rose rosette (or rose witches' broom), rose leaf curl, rose spring dwarf and rose wilt. Other disorders are caused by hormonal imbalances or other types of incompatibility between the graft and the rootstock of unknown aetiology, such as rose bud proliferation, rose dieback (or rose stunt) and frisure. Techniques for diagnosing viruses in roses and methods for their control are described." http://www.cabdirect.org/abstracts/19981005603.html --------------------------------------------------------------------------------- There was an early (1962) paper that reported tomato ringspot virus infection in U.S. roses (Google Scholar does not reach back that far. More recent papers questioned their results.) http://scholar.google.com/scholar?start=10&q=%22TOMATO+ringspot+virus%22+roses&hl=en&as_sdt=0,36 -------------------------------------------------------------------------------------- The name given to a virus can be misleading. It is mainly of historical interest and does not indicate the wide range of plants that that virus can infect. For example, Tomato Ringspot Virus can infect many types of weeds (including dandelion). http://www.apsnet.org/publications/plantdisease/backissues/Documents/1984Articles/PlantDisease68n03_242.pdf --------------------------------------------------------------------------------------- Tomato ringspot virus is in the genus Nepovirus which normally are considered to be nematode transmitted viruses. However there are instances where tomato ringspot virus transmission is thought to be more complex: "Transmitted by a vector; a nematode (and also, non-specifically by insects and mites - Aphis gossypii, Myzus persicae, Melanopus sp. Epitrix hirtipennis, Thrips tabaci (possibly nymphs) and Tetranychus sp.); Xiphinema americanum; Dorylamidae. Virus lost by the vector when it moults; does not multiply in the vector; not transmitted congenitally to the progeny of the vector; does not require a helper virus for vector transmission; transmitted by mechanical inoculation; not transmitted by contact between plants; transmitted by seed; transmitted by pollen to the seed." http://pvo.bio-mirror.cn/descr809.htm Note, the above are possible modes of transmission based on observation with other plants, the actual mode of transmission in roses has not been determined.