Recommend fungicide (or something else?)

Asked September 4, 2020, 2:46 PM EDT

Hi there, I have some tuberous begonias in large pots outside. I just threw away a plant that I'm fairly certain has died of Rhizoctonia. (One stem wilts and loses all turgor and turns brown/black at the soil line, and then the rest of the stem and leaves die. I didn't notice any spots or webs. I didn't water it very often, but enough to keep the soil moist once it almost dried out so I don't think I was overwatering.) I found Rhizoctonia online and it seems the best fit, and the recommendation was a fungicide but there was no specific recommendation and I don't know anything about fungicides. I'm sorry I didn't take a picture to share. A plant in the next pot now appears to have it and I threw it out too. :( I also have some impatiens, which I noted online are also susceptible to Rhizoctonia. So far they seem ok, but they are situated close by. So my question is, what do you recommend? Thank you.

Marion County Oregon

1 Response

Just from a description it's difficult to determine a cause for the problem on the Begonia. From the PNW Disease Management Handbook, there are a couple of potential causes, which I include as links below. Note the cultural control recommendations. Most of the pesticides listed are for commercial use only, those for home use are marked with an "H". Fee free to write with questions.

Black Root Rot:

Stem Rot: