Hi folks and thanks for reading this. Attached is a photo of a streptocarpus leaf that I noticed has an obvious problem. Not sure WHAT is causing this. Under a magnifying glass I do not see any insects at all although I suspect possible mites. I have treated with Bioadvanced houseplant insect & mite control for the time being.

Has anyone else seen this and if so do you know what causes this? Thanks in advance for any replies.

Hi,
I have no idea. You may want to add pictures of the whole plant and pot for others to assess other possibilities. And describe (How long have you had the plant? Your general experience level with it, or plants in general, etc)

I wonder if it might be some type of rust, a fungal issue that can be caused by humid conditions? Another possibility might be soil pH being out of whack (over fertilization, or lack of sufficient nutrients).

It might be a good idea to isolate the plant from any others in the area and remove the infected leaf/leaves until you can determine the exact cause. If it's a fungal rust issue, the spores can spread to other plants.

When you water, do you wet the foliage? Leaves of streptocarpus, like its AV relatives, have a pubescent (fuzzy) leaf surface that doesn't tolerate water being left on the foliage to dry. The fine, hair-like appendages (trichomes) found on both the adaxial (top) and abaxial leaf surfaces will quickly rot when water is allowed to collect there and dry. I see this same symptom in streptocarpella when I'm looking for bedding plants, a plant I always enjoy growing. It's often difficult to find them with pristine leaves w/o spotting. I'm very careful not to wet leaves as I water .... and especially careful not to get fertilizer solution on the foliage.

Al

No I do not get water on the foliage. Had the plant almost a year. Fertilize with half strength miracle grow once every 2-3 weeks. Bright shade, no Sun. I suspect possible mites so treating it for that. Have removed any damaged leaves. Streps for some reason have been hard for me to grow for some reason even though I have a pretty green thumb. They should be easy, for all intents and purposes they are supposed to a very easy

The struggle continues.....

Streps also challenge me.
I had my best luck with one under my grow light for a while getting strong, then it bloomed in the bedroom by a bright window for quite a while. But it died though I forget just why.

I treat 'em like every other herbaceous plant in a pot with the exception of being as careful as possible to avoid wetting foliage with water or fertilizer solutions. I grow them in a very fast-draining soil with at least a 75% fraction of pine bark, fertilize at every 3rd or 4th watering at recommended production rates, and deadhead regularly. I have a lot more trouble finding plants with pristine foliage than keeping pristine foliage pristine.
Al

Good responses, thanks.

I refuse to give up mastering these, it shouldn't be this difficult. Thanks for all the replies so far. And wacky me, I just ordered a "Purple panda" strep yesterday. I have also read that they don't like it too hot. MAYBE that is some of my problem. I don't have central a/c and it gets up to 90 F. in the house on summer days.

They'll LOVE a summer outdoors, and will gladly show their appreciation. In winter, they'll likely want supplemental light and controlled humidity (>50%) to do well. I've always grown them outdoors in full sun.

Too much light and too much heat are two different physiological issues. Too much light causes a CHEMICAL reaction in leaves, photo-oxidation/ sunburn. As over-excited photosynthesizing machinery returns to a normal state of (molecular) excitement, a free O- free oxygen radical creates H2O2 (hydrogen peroxide), which attacks the first organic molecule it contacts and oxidizes (bleaches) it. This usually results in brown spots involving the middle of the leaf and occasionally the leaf tips and margins. Usually though, tips and margins are less involved because they dissipate heat faster than the thicker middle part of the leaf. Heat is incidental to the reaction that causes photo-oxidation.

Over-heating is not a chemical reaction. It is the result of passive (solar) heat gain that results when little bundles of magnetic energy (light/ photons) strike the leaf surface where magnetic/ light energy is transformed into heat energy. Because the plant has fuzzy (pubescent) leaves, the leaves have a pronounced layer of still air (boundary layer) which surrounds leaves and acts as an insulator to hold in heat and allow it to build in leaf tissues. You can increase the amount of light your plant will tolerate if you add a fan to the room it's in when they are in direct light. The moving air disrupts the boundary layer of air surrounding the leaf, which allows heat to dissipate into the cooler air created when the boundary layer of air is disrupted.
Al

Most houseplants will tolerate much more sun that we think as long as there is air movement to prevent the stress from passive solar (heat) gain.

Thanks for the info Al.

tapla said:
Most houseplants will tolerate much more sun that we think as long as there is air movement to prevent the stress from passive solar (heat) gain.

I've not heard this before and can't find more information about it. Can you please provide some resources?

@ tapla very creative technique to add more space to the hand rail on the deck by adding the wire shelving unit.
All your beautiful plants are all lined up for display out in the air, light, and sheltered shade. Perfect for a summer day.

Al

Look at that bonsai ‼️ … could we see a close up.. and of all your pretty blooms.
And you creative vignettes.
Beautiful…