u/zezzy_

My parents split up last year and my mom moved out of the family house. She left behind a lot of plants, both in and outdoor ones, that my dad won't take care of, so the only care they get is from me, when I visit about once a week.

This oleander is one of two that my mom planted outside in the back garden. While the eastern European climate (7b) is not exactly ideal for them, they've done well for the past few years. However, unfortunately last winter was a historically cold one and they weren't adequately shielded from the frost, so they both almost died. I say almost, because after I cut them completely bare in April, and have been watering and fertilizing them, they've started to slowly put out some small sprouts (as seen in photos 4 and 5). They get full light pretty much the whole day, since they're on the South side of the house. They've been getting watered mostly by the rain, but I'm hoping to get either my dad or a neighbor to water them daily from next month.

Now I was just watering and fertilizing them and I noticed this white spotting at the base of one. I took my shears to the base of a dead branch that was coming out of that area and it felt soft and mushy. I don't have experience with fungal infections, but this seems to me like just that. What is it and what do I do? Are there any DIY solutions, or if not, what products should I get to treat this?