Bionomics and control of the nigra scale, Saissetia nigra

Abstract

S. nigra is recorded on 161 spp. of plants in California and 148 spp. elsewhere in the world. Taxonomic descriptions are given of all stages. Its establishment in California was first reported in 1920, and in the period 1936-40 it was exceedingly prevalent on trees and shrubs in the coastal region. There is but 1 generation a year. The adult stage is reached in Apr., May or June. Egglaying extends from about the middle of May until Feb. Very little growth occurs during the summer, fall, and early winter months. Rapid growth begins in late winter. Reproduction is parthenogenetic. The av. number of eggs per [female] is 628. Many predaceous enemies are named. 24-25 spp. of Hymenopterous parasites are recorded from various parts of the world. Each of the parasites is briefly discussed. A sp. of Torulopsis or Rhodo-torula, a symbiotic organism, is present in large numbers in all stages of the scale. In the period 1939-40, the scale became almost exterminated in southern California from causes ascribed to natural mortality. The author discusses the possibility that the near extermination of the scale may have been the result of a disease caused by a virus or a microorganism. The parasite, Metaphycus helvolus, has been an important natural enemy since 1940. Light-medium oil spray, used at the rate of 1 1/2 to 2 gallons to 100 gallons of water, applied in late summer or early fall, has given satisfactory control. || ABSTRACT AUTHORS: R. H. Smith