When a risk materializes and becomes an issue, the project manager should work with the relevant stakeholders to implement the risk response plan that was prepared during the project's planning phase. This is in line with the PMI's principles, which suggest that risks should have predefined response plans that can be activated when they occur. The implementation of the risk response plan is a proactive step to address the issue and mitigate its impact on the project1.
References:
* Project Management Institute (PMI) standards and publications.
* PMBOKGuide - Sixth Edition.
* "Plan Risk Response for Your Projects" - Project Management Academy2.
* "PMP Exam Strategies for Risk Response: Mitigate Risk, Avoid, or Transfer" - Project Management Academy3.
* "Risks vs Issues: Why most projects fail" - PMI4.
* "The Difference Between Risk and Issues in Project Management" - iZenBridge5.