Patent ID: 8187618

Claim:
A solid pest control unit having a mass of about 3 to 45 grams, the unit comprising a composition comprising about 30 to 90 wt.-% of a plaster matrix, the matrix comprising a plaster having a high compressive strength of at least 500 lbs, per square inch and having a hardening amount of water, and about 2 to 15 wt.-% of a polypropylene powder buoyant agent having an internal void, the void comprising about 2 to 10 wt.-% of a Bacillus thuringiensis israelensis particulate microbial pest control agent, wherein the unit is sufficiently hard to be distributed over large areas by mechanical means, has a surface area of about 10 to about 50,000 mm 2 , and when immersed in an aqueous pest breeding site, the plaster matrix causes the unit to sink to the bottom of the site and release the polypropylene particulate buoyant agent to the surface, providing up to 154 days of control days of control with an effective amount of the pest control agent, wherein the unit when dry does not release the agent, and wherein the combination of polypropylene powder and the microbial pest control agent, when soaked in water for more than 24 hours, demonstrates a specific gravity of less than 1.0.