Sunflowers Dying? :(

I noticed the very bottom of one of my sunflowers was brown a few days ago, today the problem had gotten much worse. Can anyone tell me what the problem is or, preferably, how to resolve it? Please, ignore the nettle in the picture, I'll pull it one day.




Thanks as always. Edit: I left the bug in picture 2 on the off chance it was somehow relevant.

 

It may be a few things. A snail or slug may have attact the base and caused damage with then has got infected with a fungal disease.

Or it might be Verticillium wilt which can attact sunflowers at the base.

Sorry I cannot give you and help with solving the problem.