Croton Need Help Please !
Hello, I have my croton for 5-6 years now, it is indoor since the start. It never had any diseases or problem before. But since 3 weeks - 1 month now leaves are dropping like crazy. I don't detect any pests or mold. I put it in a new terracotta pot (with drainage hole) just a little bit bigger than the last one in November, and beside that, no other change. It's still at the same place than always, I water it when I know it's thirsty (from the position of the leaves I know and never had problem with that). But now the leaves are just continuously dropping. The petiole of the dropping leaves is yellow (usually green), and all the leaves even those still attach to the stems have dark-black spots like INSIDE the leaf, near the base of the leaf and the petiole. We can see them when looking through the leaf and a spot of light. Also, the texture change exactly where are the spots, it's like a polka dots texture. And the end of the stems are kinda black instead of green. I live in Montreal and it was really freezing outside latelly and I had to open the door near the plant a couple of time (like 10-15 seconds) for a some days in a row... do you think this can be signs of freezing ? Otherwise the leaves are ok, the edges, the tips are ok, no yellowing, no browning... everything bad is at the end of the stems, the petioles and the base of the leaves. On some stems the leaves are matte and not shiny anymore. See images please. I don't want to lose my croton ! Thank you very much for your time !
Certified GKH Gardening Expert
I am, definitely, seeing symptoms of bacterial infection on the leaves and stems. It is likely that the change to a new container started the process.
Depending on the quality of the soil, where you got it, and how well it was taken care of at its location, it could have been infected soil. The best way to know if a soil is still good is by smell.
This should smell "earthy" and can smell of mushrooms or just an overall "soil" smell. If it smells of rotten eggs, sulfur, or in any way "sour" you should not use it. This will mean that bacteria has taken over.
If you know that the soil was not infected prior to planting, then the next likely cause is overwatering.
It is best to keep in mind that a plant will not act as it should for a little while after transplanting. It will not be a good idea to go by looks of the plant when watering in a new container. You will want to, physically, take measurement with your finger, or moisture meter. This measurement should be taken about 3 or 4 inches down in different areas of the soil to ensure that it completely dry down to that depth before watering again.
For now, I would treat with a fungicide, and take careful measurement between waterings, until it recovers.
These articles will help: https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm