In a message dated 14-Apr-04 1:42:34 PM Pacific Daylight Time, jshields104@insightbb.com writes: > Another way of cleaning up virus infected bulbs is by heat treatment. It > undoubtedly varies by bulb species and pest species, but 55 C for an hour > is perhaps close to what you can do. Rather than discard valuable but > virus infected bulbs, try heat treating them first. > > I don't know, does heat also kill mycoplasma? > Jim ~ This is a concept rather widely believed. While it may be true in genera other than Narcissus, I stand by my statement that a plant, once infected with virus, is best destroyed or kept isolated. I still isolate many narcissus thinking I would use them for their genetic material. Now, however, I am questioning even that practice since there is evidence that daffodil viruses can be seed transmitted. I think it fair to say that all clonally propagated plants will, sooner or later, contract one (or more) of the viruses known to infect their genus. Bear in mind, there is no guarantee that virus spores won't survive any form of heat treatment only to re-infect when conditions are appropriate (the propagule must continually be ELSA tested for any degree of certainty). In heat treatment of Narcissus, at best, all one can hope for is a diminution of symptomology, not a "cure." I still stand by my belief that once infected, virus in a plant is incurable. On the other hand, what often happens as a result of heat treatment is that viral activity is diminished for a year, or two, leading to healthier appearing plants and to the belief that a cure has taken place. Heat treatment in the form of a circulating, hot water bath in an insulated tank kept at 114 deg F (45.6 C) for three hours is the recommended treatment for the occurrence of the bulb and stem nematode (Ditylenchus sp.), the absolutely worst event to befall a daffodil (or any tunicate bulb) grower! At this temperature range, there is a very fine line between curing the infestation and the death of the bulb! The colloquial name for such treatment is "cooking," and for sound reason! I have heard that there exists in Holland a heat resistant form of this nematode that has (most likely) arisen from sloppy heat treatment practices over the years. Woe to one who contracts this one!!! Over the years, the best advice I have heard, has been (and not entirely tongue-in-cheek) to sell the place and move and start over!! Formalin (formaldehyde) has long been the recommended additive to the hot water bath to combat fungus (e.g., fusarium) at the same time. In many places, this is now a restricted chemical, if even available any longer, even though this is a naturally occurring substance. There are some newer replacement chemicals that have come into the marketplace that have been shown effective against fusarium and the fungi infecting the outer scales of the bulb. Dave Karnstedt Cascade Daffodils Silverton, OR 97381-0237 email: davekarn@AOL.com