If you mean a roughly ladybird sized red beetle rather than a mite, then its Lily Beetle - pick off and kill by hand, or use a Provado spray, though be aware this spray is dangerous to bees.

keep an eye out for the orange looking grubs, they do most of the damage. p.

The only way to deal with these pests is to check over the lilies several times a day and carefully pick them off and crush them. If you do not they will ruin your display for this year. They are very easily seen.

The bright red lily beetle WILL drop when you try to get it,so put something underneath to catch it.