I starting using this release in February. It says it's a pre-release. version v0.18.1.0rc1 (64-bit). "This is a pre-release test build - use at your own risk - do not use for mining or merchant applications".
Assume it is now a full tested release. Do I need to reload the qt?
The rc1 release of the 0.18 branch will work fine, but if you want to get rid of the warning I would recommend updating to the released version:
https://github.com/myriadteam/myriadcoin/releases/tag/v0.18.1.0