As Ron suggests above, make releases early in the season as soon as night temperatures remain above about 40′ F. Numbers depend on host density and distribution of the scale. The predator is very reproductive on scale crawlers, so putting 10 to 40 beetles per hotspot can become a greatly expanding population spreading through the forest for the rest of the season if no harm is done with pesticides. A trial in a block like Ron Evans did for pine scale and pine needle scale is the only way to develop a protocol. (Be mindful of the interference from ants as well as pesticides.)

Depending on where you are located in Wisconsin, I would estimate a mid to late May release would be better. Typically in central Illinois, I target the first week of May for my releases. What types of scale are you trying to control? Lindorus will not survive a zone 5 winter. Ideal release times target scale hatch and the crawler stage of their life cycle. We try to time our releases so that night time temperatures do not fall below 40 degrees F. I have seen Lindorus survive a 28 degree night, but don’t think they will survive much colder than that.