Yes, SILKWORM is a Scrabble word!

Letter values in Scrabble US: S 1, I 1, L 1, K 5, W 4, O 1, R 1, M 3.

Is it a valid word?

SILKWORM is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

the commercially bred hairless white caterpillar of the domestic silkworm moth which spins a cocoon that can be processed to yield silk fiber; the principal source of commercial silk
larva of a saturniid moth; spins a large amount of strong silk in constructing its cocoon

Also: giant silkworm, wild wilkworm.