This quest is not available in game.
Deliver the Unloaded Zapper and 5 samples of Atal'ai Haze to Larion in Marshal's Refuge.
You're in luck, <name>! I've been working on some of my own experiments while Marvon's been gone, and one of them is a short range bug zapper. With just a few adjustments, it should be great for ridding yourself of those Bloodpetal pests.
I can let you have one of my zapper prototypes, but you'll still need to collect the fuel. You can get the necessary Atal'ai haze that the zapper needs in the temple of Atal'Hakkar. The deep lurkers, murk worms, or oozes are the ones you'll need to get it from.