Is this viral or what....

I had three Graham Thomas seedlings come up this year. Very early on, two seedlings displayed brown markings on the leaves. I destroyed one of the two immediately because it had the light green foliage of Graham Thomas rather than the dark green (and impressed veins) of the supposed dad (Knockout)and it also appeared to be virused. I went ahead and kept this one because it seemed to outgrow the markings for most of the summer and it also clearly had KO in it. (I also kept the other light green one because it did not display any signs of virus.)





It doesn’t yellow or defoliate the foliage in any way. As you can see the plant is almost four feet tall in its first year and is still completely foliated at years end(disease resistance similar to KO).

If this is a seed transmitted virus then it kinda ruins my plans to take this seedling any further (except maybe as a pollen parent). Is anyone aware of Graham Thomas having a seed transmittable virus? Technically I guess I will get my answer next year when I grow out seedlings from this rose (I got many hips from it this year).

It doesn’t look viral to me. It looks like a form of blackspot. Knock Out gets blackspot here, but it doesn’t drop its leaves quickly.

Looks like some form of Cercospora. Roses who get very little blackspot are prone to it.

Patrick

Could it be sunburn? I had some seedlings that were very sensitive to sunlight. Some defoliated entirely and had to grow a new set of leaves for the rest of the season.

Rob

Check the reverse of the leaves to see if there are tiny bugs attached to these these browned marks.

Hi Jon,

It could be viral and what suggests that to me is that there are archs with green tissue and necrosis around the outter portions of the arches. If you are willing to send some cuttings with leaves with symptoms of both the seedling and Knock Out I will pass it along to Ben Lockhart and try to root them for further research if they test positive. I have been working with him and Dimitre Mollov at the U of MN with the characterization of new rose viruses. There are multiple ones we are in the midst of characterizing. Ben spoke on the rose virus research at the 2007 spring ARS National Convention in St. Paul.

Sincerely,

David Zlesak

David shoot me a mail to tnbigbrother at yahoo with an address and I will mail clippings of Graham Thomas and the affected seedling wed. or thurs.

Jon, I’m going to make several comments, and perhaps one of them will make some sense. First, there are several things going on in the pictures. The semi-circular notches on the edges of the leaves is insect feeding damage. Probably not caterpillars, which would have eaten most of the leaf. Think root weevils, or possibly in mid-summer, leaf cutter bees. The small spots with grey rims in the upper left corner of picture number one are fungus–botrytis? The spot might have started as a puncture wound from a spine, or the like. The fungus may have been secondary, moving in after the initial damage.

The color pattern could be blackspot–but then it probably would have become much denser/darker. I think RosariumRob is on the right track, but I’d call it “environmental shock” rather than sun burn, which probably would be more localized.

Was this seedling taken from a greenhouse directly out into colder conditions outdoors while the leaves were still “soft”? The bottom picture seems to show that upper leaves didn’t suffer the same effect.

Ken

Thank you all for your comments. I maybe should clarify a few things. These markings showed up in the first few weeks of life, while the seedling was still inside under lights (before I set it out), and has persisted throughout the growing season (all year). I would maybe think it was fungal but the coloration does not extend to the underside of the leaf (the underside looks healthy and green). It does take a while for it to “set in” so that the growing tips always appear healthy. I am aware that I have a healthy sawfly population. I also have a healthy wasp population that comes and hunts the sawfly larvae. I also spend some time during the summer removing rose slugs by hand myself… I’m not a big believer in chemicals and so by this time of year all my roses have munch spots on them.

Could it be from the fertilizer you are giving to this plant or perhaps the soil that you have it planted in might be bad? I would change the soil and stop feeding fertilizer if in fact you do.

I have transplanted it at least twice (and maybe three times… pot upgrades). My potting soil is fairly consistent.

Equal parts of peat, river sand, and clay/loam topsoil. I fertilize maybe twice a year with regular strength miracle grow (1/2tsp per 2 gals… I’m not a big believer in fertilizer either).

I think that the rose is sensitive to something in the soil. I have a seedling that did wonderfully in a pot, planted it in the ground and the leaves started getting these blotchy white spots on the leaves. Took it out of the ground and back into a pot with Miracle Gro potting soil and it started doing wonderfully again. Roses are sensitive buggers, they will tell you when they don’t like something.