The devourer's attack has the additional effect of attaching "acid spores" to anything it hits. A unit affected by spores will be revealed (if cloaked), have its attack speed slowed by 1/8 per spore, and take 1 point of additional damage from every attack for every spore attached. A maximum of 9 spores may affect a target at any one time. Spores will disappear after a period of time.
The fast firing and bouncing attack of mutalisks benefit greatly from the acid spores. Against a group of targets splashed with 9 spores a single mutalisk can deal 18 damage on its first attack instead of the normal 9 damage, this also applies to the mutalisk's second and third attack which makes it effective take out high armor targets faster, like battlecruisers and carriers, and able to go toe to toe with area-of-effect anti-air units like corsairs and Valkyries.
Devourers have a very slow rate of fire, and the attack travels slowly. If a devourer moves before the glob of acid strikes, the glob disappears. The devourer's slow speed and rate of fire also makes it vulnerable to hit-and-run attacks from groups of scouts and wraiths.