Virus questions

Mary Sue Ittner
Fri, 12 Jul 2002 20:04:11 PDT
Dear Robert and Bill and Diane,

Thanks for your responses. I don't think I am going to try tissue culture, but I read that article and it said microwaves were uneven for sterilizing soil. And Bill is probably right, that even if the corm looked all right, it wouldn't be. So perhaps I am wasting my time. I wrote most of this before reading Diane's response, but it was similar to something Jack Elliott wrote a number of years ago about having a plant in his yard that bloomed well and was vigorous, but probably was virused and when he introduced another plant he grew from seed the second plant was affected and showed symptoms.

I had remembered that Will Ashburner on the IBS forum had once written that his wife Chris used milk to treat a plant and so I looked it up in my files since I wasn't sure exactly what it was she had done and for what. Will referred to an article in New Scientist magazine espousing the virtues of milk for controlling powdery mildew. A rex begonia that they had brought back from the USA and Chris had nurtured had gotten powdery mildew. In spite of Will's advice to the contrary, Chris decided to follow the description in the article and sprayed the plant and it recovered.

I wrote Will to find out more and learned the dilution was one cup per litre (I assume that is water.) He said it washed off easily so you had to respray. 

When I was searching for anything I could find about viruses I found on the web a very detailed analysis of different viruses published by the Biological Research Information Center (BRIC) of Korea. It listed a whole lot of viruses that affected bulbs and how they were transmitted (usually aphids or mechanically, but sometimes nematodes, thrips, pollen, seed, leaf hoppers, fungus, and even not known.) I transferred this information to my computer and made it into a word table that I could read which took quite a long time as is often true when copying something from the net. If you looked at it, you would be reluctant to grow Alstroemeria as it seems susceptible to lots of different viruses. All my bulbs had the same class of virus  and the article said it was transferred by aphids and mechanically. So I wondered if when I cut off seed pods if I could spread it around. It didn't define what mechanically would mean. Still my specific bulbs weren't listed on this table. If anyone wants my table and can get word documents, write my privately and I'll send it.

I don't usually see aphids on my Brodiaeas, but am always fighting them on my Alliums. I was interested in reading in Jane's article about her frames that she uses a systemic as she pots to keep the aphids at bay. I know I wouldn't want to do that. I only once used one on Agapanthus that got mealy bugs and got so conflicted I ended up digging them out when the treatement didn't work and I knew I'd have to keep doing it. If Mark is reading, how do you keep the aphids off your Alliums? I try washing them off and using a spray that combines pyrethrum and canola oil which seems to kill them, but they keep coming back.

As I have tried to find out more I have learned that Sparaxis are prone to virus and that probably many of the commercial hybrids people buy are virused. I don't think anyone would have thought the one I was growing was virused. In fact Roy Sachs saw it in bloom and thought it was really beautiful the year before and it looked much the same this year. I recently looked at an old picture of one I have had a long time that has always bloomed well and increased and if I looked at the flower carefully there was an interesting pattern break so it could have been virused for years.

I know that Bill Dijk sterilizes his soil and I think he uses chemicals. Rachel and Rod Saunders have a huge machine that handles a lot of soil at one time and uses heat. I have reused soil without sterilizing and haven't felt it was much of a problem except for some of those tiny corms like Gladiolus tristis and Geissorhiza inaequalis and Oxalis that can appear unwanted in another pot. But Rod and Rachel made me feel it was important to sterilize if you were going to reuse soil. It seems unclear whether virus can be transmitted by soil, but the whole area is very murky.

There probably won't be anybody studying this unless it affects cut flowers, which is maybe why so much is known about Alstroemeria.

Mary Sue

From ???@??? Tues Jul 16 22:19:31 2002
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Date: Tue, 16 Jul 2002 08:58:01 -0700 (PDT)
From: Chad Schroter <>
Subject: Difficulties with Dierama
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I am looking for some tips on growing Dierama in the
garden. I am in a Medit Zone 9 climate (Los Gatos
California) and my soil is amended rocky - silty -
clay which works easily so the clay content is not
very high. I have grown various D. pulcherimum and
dracomontanum from seed and have brought some to
flower (third year) only to have them dry up and
dissappear forever immediatly afterwards. Whenever I
have moved plants or bulbs(other that the seedlings
planted from the seed pot) they have died or failed to
re-grow. My successfull plants have been in relativly
dry soil with a high organic content that gets scant
drip irrigation or are at the fringe of irrigated
areas, not the moist soils recommended in literature.
Seedlings started in moister areas have not survived
so far. A group of D. pulcherimum seedlings blooming
now are turning yellow (drying) after flowering - is
this normal for the flowering bulb ? Do Dierama's need
a rest period in winter/late summer or are they
evergreen ? Any suggestions appreciated

Chad Schroter

From ???@??? Tues Jul 16 22:19:31 2002
To: "Pacific Bulb Society" <>
Date: Tue, 16 Jul 2002 08:58:01 -0700 (PDT)
From: Diane Whitehead <>
Subject: Difficulties with Dierama

I have big clumps of dierama that have been in place since they were seedlings. They flower spectacularly. My soil is sandy (There is a commercial gravel pit nearby), so I need to water them. I used to think that South African plants ought to be in unwatered areas, like Mediterranean or California natives, and when they died, I assumed they died from cold winters. Then I looked at photographs of plants in the wild and discovered some of those plants actually grow on streamsides, so I now plant anything from South Africa near a sprinkler.

Dieramas are evergreen, and the foliage is massive, so that they need water year round to maintain it. In Africa, they grow in moist grassland, and don't grow in areas of summer drought. (Information from Dierama The Hairbells of Africa by Hilliard and Burtt)

Last fall I dug up a clump that had grown too large for its space, broke it up and put the pieces in a shady pile of leafmould to recover. They are now putting up new growth. I just went out to look at the established clumps, which are currently flowering, to see if they are putting up new leaves too. I can't see that they are, so I don't know when mine actually grow new leaves. The old leaves remain green well past the time that the new leaves grow, so it is hard to notice when that is.

Diane Whitehead Victoria, British Columbia, Canada
maritime zone 8
cool mediterranean climate (dry summers, 75 cm rain per year almost all from Oct to May)

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