Scottish Rock Garden Club Forum

Cultivation => Cultivation Problems => Topic started by: Alex on February 29, 2020, 10:03:24 PM

Title: Juno Iris leaf problem
Post by: Alex on February 29, 2020, 10:03:24 PM

Hi all,

I have one Juno Iris narbutii which has put up leaves as illustrated below. The lesions appear particularly on the underside of the leaf (second photo) but show through clearly to the upper leaf surface too. I feel they may be getting more extensive since I noticed them a week or so ago, but not sure. Any opinions? Could these be necrotic spots from a virus? Or does it look like insect or physical damage of some kind?

Grateful for any thoughts. Thanks very much.

Alex

Title: Re: Juno Iris leaf problem
Post by: Gail on March 01, 2020, 07:53:39 AM

Thrips (of which there are many species) can cause that kind of damage - fast moving little beasties that always lurk on the opposite side of any leaf you are inspecting.

 

Title: Re: Juno Iris leaf problem
Post by: Steve Garvie on March 01, 2020, 10:25:14 AM

Under glass Thrips and Red Spider Mites can cause such damage but this would require heavy infestation. Thrips are usually 0.5-1mm in size and RSM <0.5mm. Both should be evident on direct inspection with a magnifying lens. RSM usually produce some fine silk webbing and Thrips usually leave tiny black excrement spots peppered over the damaged areas of the leaves. In the absence of these virus would have to be the most likely option. Your image is not dissimilar to some images of various Topsovirus which can infect Irises. Apparently there are many potential host plants and each exhibits differing appearances when infected.
Examples are Impatiens necrotic spot Virus and Iris Yellow Spot Virus linked to below:

https://www.forestryimages.org/browse/detail.cfm?imgnum=5583439 (https://www.forestryimages.org/browse/detail.cfm?imgnum=5583439)
https://www.researchgate.net/figure/Iris-yellow-spot-virus-infected-onion-plants-Notice-the-white-lesions-and-green_fig2_312323967 (https://www.researchgate.net/figure/Iris-yellow-spot-virus-infected-onion-plants-Notice-the-white-lesions-and-green_fig2_312323967)

Title: Re: Juno Iris leaf problem
Post by: Alex on March 01, 2020, 05:32:59 PM

Thank you so much, Gail and Steve. It could be rsm or thrips but I don’t see any pests and there aren’t other plants around with the same damage. I think it does look a lot like that Topsovirus image, too. I have a low threshold for virus suspicions (Pleione grower) so I’ve isolated it. I’ll have to think about whether to give it another chance next year or not.

Thanks both again.

Alex