Copyright © 1991 Published by Elsevier Inc.
Received 31 July 1990;
Colonization of additional natural enemies of Icerya purchasi Maskell (Homoptera: Margarodidae) in Israel was considered because of the frequent outbreaks of the scale during the 1980s and the chronic severe injuries to certain ornamental plants whose toxic effects through the scale reduce the effectiveness of Rodolia cardinalis Mulsant (Coleoptera: Coccinellidae). Colonization trials were conducted with the parasitic fly Cryptochetum iceryae Williston (Diptera: Cryptochetidae) collected in southern California and with Rodolia iceryae Jenson sent from South Africa. Rearing experiments of both natural enemies were conducted using I. purchasi and I. aegyptiaca (Douglas) infesting different plant species. C. iceryae developed on I. purchasi growing on 17 host plant species. I. aegyptiaca was not affected by the fly. R. iceryae could not complete its development on either I. purchasi or I. aegyptiaca. C. iceryae was released at nine sites planted with Erythrina corallodendrum, Spartium junceum, or Retama raetam infested with I. purchasi. In citrus groves, after 2 years and following several releases, it is still uncertain whether C. iceryae has become established. C. iceryae was acclimatized at all sites planted with E. corallodendrum, S. junceum, and R. raetam and suppression of the scale was achieved in 2 years, probably because of the lack of significant competition with Rodolia cardinalis. I. purchasi populations were very sparse in the sampled citrus groves. Only in one site did we observe a rapid switch from the latent epidemic phase. This outbreak resulted in serious damage to the trees and was followed by a rapid breakdown of the scale population due to a sharp increase in the R. cardinalis population.
Author Keywords: Icerya purchasi; Cryptochetum iceryae; Rodolia cardinalis; Rodolia iceryae; Spartium junceum; Erythrina corallodendrum; citrus; biological control
*1 This paper is a contribution from the Agricultural Research Organization, No. 3043-E, 1990 series.