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cicivacation

Virus Management: Know it

9 years ago

What virus signs are you looking for?
Stunted growth even when there is space to grow, twisted leaves, yellow
margin following veins, circular spots or a 'V' of lightened leaf tissue
along the main vein near the stem. Here are some images with clear virus sign:



Check this link out for more
examples:http://www.dahlia.org/uploads/images/DIYpdfs/VirusBrochureJune2015.pdf

Comments (8)

  • 9 years ago

    Thank you!

  • 9 years ago

    cicivacation: thank you for all of your informative posts here: very helpful!

    Several plants showed signs of what I think may be virus infection back in mid to late July....the hottest, driest, most stressful weeks of this season. As rain increased and temperatures 'cooled' a bit, plant growth took off; bud formation increased; aborted buds decreased; leaves with virus-like symptoms all but disappeared. The last 7-8 weeks have been terrific.

    Since I am not certain these plants DO have virus infection...why should I start discarding plants which might be infected with virus, if the virus seems to only have manifested itself via some yellow leaves in July?

    Is it possible that my plants can continue to just outgrow the infection next year? They seemed to this year, and it was a very stressful season.


  • 9 years ago

    I said something similar in another post, that I had decided my plants didn't have a virus for that reason, they responded well to cooler temps. Also, I grow from the same tubers in two locations and did not have issues at the other one. So unlikely that it was a virus that overwintered in my tubers. Cicivacation asked for a picture but now they are frost burnt, too. Maybe next year.

    It is a problem that most virus symptoms can also be symptoms of other problems. But we are taking a calculated risk when we wait and see.

  • 9 years ago

    I don't think anyone is arguing with removing virused dahlia plants. I think its more a concern about removing any plant that shows signs of sickness that may or may not be virus. Especially us novices who aren't familiar with the symptoms of all of the other problems that affect these plants. Especially, for example, here in the Northeast where even very experienced growers were having sickly plants and blaming our heat and drought.

    These pictures and the benefit of your experience is very helpful and thank you again. But I wish we (all) had a cheap field test.

    Also adding a link that talks about control, not elimination, as a reasonable goal. There are four pages of pictures and information. http://www.dahlias.net/dahwebpg/Disease/Virus1.htm

    Also, Wallace23. Another grower suggested my yellowing, dying leaves were probably from mites. She was losing plants to them and they thrive in heat. You might want to google that topic. Some sources say you can see the mites, others say you need a magnifying glass. Probly more than one type of mite. My only point here is that the more we know about other issues, the more we can make an educated guess about when to destroy.

  • 9 years ago

    Amen to the cheap field test. They are currently $10 at a lab, but the subsidy for that may be going away soon, popping it back up to $40-60 per sample. My results were very illuminating, and I'm still trying to figure out results from a friend's tests with dozens of samples. Interesting stuff, but not clear-cut in the least.

    Elimination is only part of the equation. I'm thinking that a full Virus Management regime actually has four parts: Know it, Toss it, Avoid it & Advocate it. I've only touched on the first two on this forum, and will probably talk about the other two in the spring, unless there is a lot of interest in them now.

  • 8 years ago

    Tossing is a hard thing to do but it's the best thing to do!! Even if in doubt. But if u don't have anyone growing dahlias in your area and u don't sell or trade tubers then don't worry ab it if u don't want to. However, if anyone grows dahlias around the neighborhood or if u sell or share tubers, the ethical thing to do would be to toss, even in doubt. I don't mean to butt in or sound rude - but with mites- if they're causing discoloration on the leaves, then they're going to be identifiable !! By the time mite damage is visible on leaves. The mites have already reproduced to high & identifiable numbers!! All u have to do is look under the leaf for a white dustiness, small webbing & a dirty look to the leaf w/possible dark spots. I can also look up info online how to check for mites. There's a lot of info on this on the web. Mites aren't hard to detect like most claim ! It's actually pretty simple to tell if u have mites. If you've been gardening long enough, mites leave a mottled appearance on the top side of the leaves which is completely distinguishable from anything else. Including virus. I have virus infected dahlias ! Im going to pitch all my tubers & solarize my soil this winter to start fresh but I'm cutting blooms up until my first frost and this is ONLY bc I don't sell or trade tubers ! I'm also in Florida and I'm the ONLY person within 10 miles (possibly many more- Maybe hundreds, who knows!) that grows dahlias so I don't have to be considerate of their dahlias & throw mine out. For my own peace of mind & sanity however, I will be cleaning house this winter to start fresh & healthy.

  • 8 years ago

    Another comment on mites- if your leaves are riddled with mites to the point they're yellowing and dying - your going to see white dustiness and webbing on not only the top part of the leaves but the bottoms also. Please take it from someone who lives in Florida!! Our weather is insect, bug, fungus & nite heaven!! I've had mites whipe out rose bushes and much more bc I got lazy and bc I used insecticide which in turn killed the mites predators!