Should I spread each release over a large area?
No, concentrate each release. Your goal is to get the beneficial insect colonies established in the areas you have set aside for biological control. With a herbicide, you take a finite amount of material and dilute and spread the material over a large area.
In introducing a biological control agent, one takes a finite amount of material (insects) and concentrates it in specific areas. In the initial releases, one wants to concentrate the insects so the insects can continue to find each other to mate and reproduce. Also, this allows one to more easily check for the insect in future years and for later redistribution to new areas.
Biological Control of Weeds, Inc.
1418 Maple Drive Bozeman, MT 59715