Bionomics of Epiphyas postvittana, Ctenopseustis obliquana, Planotortrix excessana (Lepidoptera: Tortricidae) and Stathmopoda "skelloni" (Lepidoptera: Stathmopodidae) on apple cv 'Dougherty' in Auckland

Abstract

The genus Ctenopseustis Meyrick (Lepidoptera: Tortricidae) is reviewed and the type species C. obliquana (Walker) is redefined. The species C. servana Walker and C. fraterna Philpott are reinstated and the synonomy and characteristics of each species are described and illustrated. Populations of the three leafroller species Epiphyas postvittana (Walker), C. obliquana and Planotortrix excessana (Walker) together with Stathmopoda “skelloni” (Butler) were monitored intensively from 1976 to 1979 in an insecticide free block of mature apple, cv ‘Dougherty’ trees in West Auckland. S "skelloni" is recorded as a pest of apple for the first time. The general biology, distribution and host range of these four species is described. A key to the larvae of the four species, as found on ‘Dougherty’, using head capsule measurements together with other characters, and keys to the leafroller eggs and pupae are provided. A technique to successfully mate C. obliquana and P. excessana in the laboratory was formulated by predicting the emergence time of female pupae and enclosing one such pupa with several males. A colony of C. obliquana was initiated from the progeny of a single mated female but collapsed in the fourth generation and possible reasons for this are discussed. The life history of all four species on ‘Dougherty’ apple in Auckland is described. E. postvittana completed four generations, P. excessana three and S. “skelloni” two but the number of C. obliquana generations per year was undetermined. The seasonal and daily flight periods were determined using two suction traps within the apple block. Female flight in all species occurred shortly after sunset, generally for two to three hours, whereas male flight extended for up to eight hours after sunset. Results of the suction traps were also used to show the lower temperature thresholds of flight for E. postvittana as 7-8°C, 8-9°C, and 10-11°C for the second summer, spring and first summer generations respectively and for S. “skelloni” as 9-10°C and 11-12°C for the autumn – winter and spring –summer generations respectively. Loss through pre-establishment failure of first instar larvae accounted for the greatest amount of mortality in the life history of all leafroller species. No eggs or pupae of S. “skelloni” were found on the trees throughout the study. Egg mortality in the leafrollers was low and larval parasitism was up to 33.6% in E. postvittana and 19.6% in P. excessana. The parasite species found associated with each leafroller host are listed, the most common being Apanteles tasmanica in E. postvittana and Goniozus sp. in P. excessana. Host preferences were shown by several parasite species. Parasitism of E. postvittana by Apanteles spp. reduced the larval growth rate and head capsule size of this leafroller. Larvae of C. obliquana did not complete development on the 'Dougherty’ trees due to its resistance to this leafroller species. Laboratory rearing experiments comfirmed this and showed cv 'Red Delicious’ was susceptible. A third culivar, 'Granny Smith’, showed some indication of resistence to the larvae of C. obliquana and P. excessana but E. postvittana showed high survival rates on all three cultivars. The distribution of each species within both the study site and the trees was examined. S. “skelloni” showed a significant preference for the calyx of fruit whereas all leafroller species preferred feeding sites on the foliage. Analysis of instar – feeding site comparisons showed that leafroller larvae moved to new feeding sites several times in their lives. S. "skelloni” probably remained in their initial sites until leaving the trees to pupate.