Plant and host effects on the leafroller parasitoid Dolichogenidia tasmanica

Abstract

Parasitism by the braconid wasp Dolichogenidia tasmanica of first instar larvae of the lightbrown apple moth Epiphyas postvittana, established on four different species of potted host plants, was assessed after 2 weeks of field exposure in an apple orchard. Parasitism varied significantly between larval host plants (apple 58% , broom 59% , clover 30% , poplar 19% ). Parasitism on potted apple seedlings of the co-evolutionary host, E. postvittana, was compared in a field trial with that of two native New Zealand leafroller species (to which D. tasmanica has had exposure for 5 decades only). Parasitism varied significantly with larval host (E. postvittana, 83% ; Ctenopseustis herana, 58% ;Planotortrix octo, 26% ). Larval collections were made from mature apple trees and identification of larvae was achieved by DNA analysis for the leafroller species using PCR-RFLP of ITS1 + ITS2, and for the parasitoid by specific PCR of partial 18S. Parasitism under natural field conditions on mature apple trees was not different between larval hosts (mean 32.5% ). In laboratory studies, more P. octo larvae departed in response to parasitoid probing behaviour than E. postvittana, which is likely to contribute to the difference in parasitism rates. This study conclusively shows that D. tasmanica parasitises native New Zealand leafrollers, despite their different evolutionary origins.

Volatiles from Apple Trees Infested with Light Brown Apple Moth Larvae Attract the Parasitoid Dolichogenidia tasmanica

“…23 It is quite probable that the glue reduced the parasitism rate. The significant increase in D. tasmanica suggests specific volatile cues from the infested trees to which D. tasmanica responds, supporting the laboratory studies with two types of bioassays.…”

“…However, there appear to be some differences in the efficiency of the discovery process by parasitoids between plants. 23,24 Whether some or all of these systems are induced from the plant biochemical response to the oral secretions of E. postvittana caterpillar containing linolenoyl glutamic acid 8 is yet to be proven. …”

“…32 Trapping with Sticky Infested Leaves. We modified the method of Suckling et al 23 to confirm that D. tasmanica would be attracted to foliage infested with E. postvittana in the field by adding a sticky surface to leaves. A total of 28 potted apple trees were infested with 20−30 first instar larvae for 24 h (ensuring good establishment).…”

Fatty Acid-amino Acid Conjugates Diversification in Lepidopteran Caterpillars

“…Only domesticated silkworms have no such means of protection, but they no longer live in nature. In contrast, most of the FAC-containing species show no direct defensive reactions, with a few exceptions as shown in the case of E. postvittana, which also uses thread to escape from parasitoids (Suckling et al 2001 Tree of Life Web Project, http://tolweb.org/.] ① gutamine conjugates only; ② glutamine and glutamic acid-type FACs; ③ hydroxylated glutamine-type FACs; ④ hydroxylated glutamine and glutamic acid type FACs; O no FACs detected species seem to especially focus on feeding and sleeping to grow faster, which characterizes them as serious pests (Fig.…”

Testing the impact of laboratory reared indigenous leafroller (Lepidoptera: Tortricidae) parasitoids (Hymenoptera: Ichneumonidae, Braconidae) on sentinel hosts in controlled orchard releases

“…Lightbrown apple moth, Eiphyas postvittana (Walker) (Lepidoptera: Tortricidae) larvae, exit webbing on leaves and spin down or crawl over the leaf surface when probed by the parasitoid Dolichogenidia tasmanica (Hymenoptera: Braconidae) (Suckling et al, 2001) and diamond-back moth, Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) larvae, have been observed to hang by silk from plant leaves after attack by Diadegma spp. (Hymenoptera: Ichneumonidae) (Waage, 1983).…”