Disease afflicting some herbs... what is it?

[Sinajuavi]

We've had over the past few years several herb plants with some disease which kills one branch at a time, eventually killing the plant. But while some branches are sick and wilting/blackening, the others continue to grow normally until they also are afflicted.

This has affected hyssop, sage, and lavender, and also Cannabis (legal here). Hitting one branch at a time, it presents very differently than fusarium or verticillium wilt, which it does resemble superficially.

 

[Chuck]

What does it affect first, limb tips or the base of the limb. Is their drooping? What are the leaves doing? We need to see GOOD pictures to make a diagnosis but it sounds like a watering issue/root rot.

 

[Sinajuavi]

I don't think I can get a pic now, as the affected plants have died and been removed for this season... but it will be back!

We don't over-water, however the soil has a lot of orange clay so drainage isn't great... this only affects those species I mentioned, nothing else.

The withering of the branch seems to start at the bottom, but it rapidly affects the entire stem. The stem doesn't droop, but the leaves do, and turn dark. It always strikes one stem at a time. The plant dies slowly, as many stems remain in good condition, sometimes for most of the summer before they succumb.

Of course in the past 3-4 years it has rained far too much, and been cloudy, unlike in the past (I'm in the VA Piedmont near Charlottesville). I've coped with this simply by always starting new seedlngs to replace those which will inevitably die. It is worst on the hyssop. Some sage plants are not affected, nor most of the rosemary.

 

[DirtMechanic]

It is in the ground. You describe root death by fungal action. The root feeding the branch above. Use agri-fos. It is very effective for oomycetes but also other problems as you read and research the label.

 

[Sinajuavi]

It is in the ground. You describe root death by fungal action. The root feeding the branch above. Use agri-fos. It is very effective for oomycetes but also other problems as you read and research the label.

Thank you! That makes sense based on my observations. The affected plants are not necessarily in proximity, but rather of certain species. Even one put in dozens of yards away comes down with it if it is a hyssop, thyme, sage, etc.

This is very bad orange clay Piedmont soil to which we keep adding endless compost. Now that I mention that, I suppose the offending fungus could have come in with the compost, some of which was bought by the truckload.

ok, I shall proceed accordingly, thanks again

 

[DirtMechanic]

Thank you! That makes sense based on my observations. The affected plants are not necessarily in proximity, but rather of certain species. Even one put in dozens of yards away comes down with it if it is a hyssop, thyme, sage, etc.

This is very bad orange clay Piedmont soil to which we keep adding endless compost. Now that I mention that, I suppose the offending fungus could have come in with the compost, some of which was bought by the truckload.

ok, I shall proceed accordingly, thanks again

Trust but verify, knowing which one it is serves up the better medicine. Still, clay holds water and you brought the food. No suprise something grew!