Dawi

This plugin disables the WordPress update notifications, as well as update notifications of different plugins. It is ideal to deliver a complete WordPress and not bother the user with alerts. Silence!
<h4>Please note!</h4>
It’s very important that you keep your WordPress plugins up to date. If you don’t, your blog or website could be susceptible to security vulnerabilities or performance issues. If you use this plugin, you must make sure you keep yourself up to date with new releases of your active plugins and update them as new versions are released.

Silence!

Disables the plugin update checking and notification system.

gr8nilay

This plugin is use to disable all your theme updates as well as notifications for the same. It will prevent your wordpress to check for new updates for each theme. This plugin is ideal for whom who have customzied the theme and won’t loose their customization at time of update.
Read This First: 
You need to keep your WordPress updated with themes and plugins so if you fail for the same then it will might compromise security of your site.

Disable WP Theme Updates Advance

Easy to install and automatically disable all theme updates.



Nice..!!

Disable all your WordPress theme updates on plugin activation.

Silence! vs Disable WP Theme Updates Advance