Vinca

[descodave]

We had a nice "strip" of Pink Vinca planted in a depression in our pahoehoe lava; anyway, today one of the plants looks yellowed & wilty; what's wrong with it? Should I tear it out? Thanks for any input!

[rainyjim]

It might be suffering from a fungal disease or maybe it's not getting enough nutrients to stay healthy.

There's really no way to tell for sure with the information you provided, if you could try to post a link to a picture maybe I could tell you more.

Refreshing to hear someone worried about their vincas : )

[Clayjacks]

With vinca, "wilty" (even when properly irrigated) is *usually* aerial phytopthera -- a fungus that vinca is prone to. "Yellow" could mean nutrient deficiency (too little) or toxicity (too much). "Yellow and wilty" could mean a root disease (like Pythium, also a fungus) -- Poor drainage/low soil porosity/just too much water. Though poor drainage *usually* isn't a problem with Puna "soils"...
Vinca doesn't like wet feet.

[rainyjim]

Fwiw,

Phytopthora and Pythium are water moulds or oomycetes - not fungi.

While similar to some fungi these oomycetes come from an entirely different kingdom than fungi - they are stramenopiles

Yay taxonomy.

: )

[Clayjacks]

Eh, both are treated with fungicides... But I get the taxonomy.

[descodave]

Thanks for your thoughts/ information guys! Should I tear the plant out so it doesn't spread to the others?

[Clayjacks]

With plants like vinca, I practice "when in doubt, tear it out." Just keep an eye on the rest -- *if* it's a phytopthera-like disease, it can spread by splashing water (hose or rain). *If* it's a root disease like Pythium, it can spread through standing water or over-saturated soils. In my opinion, vinca isn't worth treating with fungicides unless it's a huge landscape feature, or you're growing commercially. They're pretty tough if the conditions are right (pH around 6ish, low-to-moderate fertility, plenty of direct sunlight and well drained soil.)
For one plant, I'd just rip it out and watch.

[rainyjim]

If it is a root rot problem (water moulds mentioned above) then the spores in the soil (which are ubiquitous Hawaiian soils) spread the disease. Tearing out one infected plant will probably not prevent the spread of other plants.

And that's assuming it's a root rot problem. It might just be nutrient deficiency.

Typically root rot occurs in low lying areas with poor drainage. Most of puna has rocky soils with excellent drainage however this may not necessarily be the case for your specific locale.

I would give it some nitrogen and wait and see what happens.