Stethorus adults can be found in the leaf litter immediately surrounding the trunks of fruit trees, in large numbers along the herbicide strip, and occasionally in the drive row. Recent research indicates the distribution of Stethorus to be closely associated with the leaf litter distribution in the orchard. The number of Stethorus overwintering outside the orchard is unknown, but they have been found along fence rows and adjacent wooded areas. It is advisable not to disturb the area in the herbicide strip near the trunk of the tree from November 1 to mid-April. Adults begin to emerge at the tight cluster stage of apple development with peak emergence from the pink to bloom stage.
Adult emergence is usually complete by the petal fall stage.
The adults remain active in the orchard until September to late October. During early May females begin to lay eggs on the leaves of fruit trees. Egg laying occurs from May to mid-August. Although pupae are constantly in the trees, the peak pupal periods are late May, early to mid-July, and late August. Stethorus produces three generations per year in south-central Pennsylvania.