Propagation of the Oriental fruit moth under Central California conditions

does not appear. First page follows. Introduction Since 1943 the State Department of Agriculture has discovered low populations of the Oriental fruit moth, Grapholitha molesta Busck, in several widely scattered peach-growing localities in central California. The San Joaquin and Sacramento valleys which comprise this area contain a large proportion of all peach plantings within the state. These valleys have a different climate from that encountered by the Oriental fruit moth in other important peach-producing states. The very hot, dry summers and mild, foggy winters, the extensive practice of irrigation, and the very long growing season—averaging 289 days in the vicinity of Fresno (Bonnett, 1941)4—are environmental factors which may affect the future development of the Oriental fruit moth populations. In the course of a general study of the life history of the Oriental fruit moth in central California, a number of experiments were performed in the insectary at Dinuba to determine whether or not the hot summer climate of the central-valley area retards its propagation; and, if so, whether it is retarded enough to reduce the potentiality of the moth as a pest. It is the purpose of this report to describe this phase of the life-history work, and to present other observations on mating and oviposition which have a bearing on the dispersal and build-up in thinly distributed populations of Oriental fruit moths such as now occur in this part of the state. Methods and Stocks The moths were reared in a screened insectary and subjected as nearly as possible to outdoor conditions. The cages and other receptacles were constructed of light materials, thin sheet plastic and cheesecloth or gauze, in order to minimize the time required for their interiors to come into equilibrium with atmospheric conditions during rapid weather changes.