Project Methods and Results

Parasitoid and Host Identification

Defoliating lepidopteran larvae and pupae were collected from various target areas in Western Washington and reared on either artificial diet or host plant foliage to emergence of the adult moth or parasitoid(s). Larvae or pupae were maintained in individual ½ ounce, 1 oz., or 3 oz. plastic cups to ensure association of reared material, and all shed larval skins, pupal cases, and cocoons were collected and curated with reared specimens for use in species identification. (For survey coverage and methods details, see LaGasa et.al. 1997, LaGasa and Boyd 1997, LaGasa et. al. 1998). In some cases, lepidopteran larvae were also photographed to provide additional information for identification.

Reared parasitoids were initially sorted to the family level (Braconidae or Ichneumonidae) and host defoliator species was determined when possible using curated remains. Identification of host species was largely a process of comparing structural morphology between unknown host remains and the shed remains curated with identified adult moths in the WSDA reference collection. In most cases, the shed larval head and prothoracic shield (behind the head) provided sufficient information to determine species. Larval head and shield morphological characters compared included; overall coloration and pigmentation patterns, presence and position of hairs (chaetotaxy), shape and configuration of simple eyes, and the shape and pigmentation of mandibles. In some cases identification of host to species was not possible and host information provided here is presented at the highest taxonomic level feasible (i.e. Pandmis sp., and Yponomeutidae sp.). If host remains were lost or unidentifiable, reared parasitoids were curated but not included in this summary.

Associated parasitoids were sent to identifier specialists contracted for the purposes of this survey. Braconidae specimens were identified by Dr. Michael J. Sharkey, at the University of Kentucky, and Ichneumonidae specimens were identified by Dr. David Wahl, at the American Entomological Institute.

Due to needed revisions in several large taxonomic groups of parasitoids and poorly known groups, not all parasitoids were identifiable to the species level. However, all specimens were identified to genus, and discrete species were sorted to designated species numbers (i.e. species 1, species 2, etc.).

Defoliator larvae collected and reared for identification and parasitoid analysis in WSDA surveys represented a cross section of larval sampling from many plants, although the majority were from apple trees. Apple was the exclusive host-target of 1994/1995 survey (LaGasa et. al. 1996)

Overall, defoliator species identified from reared adults included some of the exotic species listed in the background section of this report, as well as other exotic species long established here and a few native species. Parasitoids reared from historically introduced exotic and native defoliator species were also identified in this survey to detect exotic parasitoid species possibly introduced with the exotic defoliators.

A total of 261 parasitoid specimens were identified in this survey, comprising 46 parasitoid species reared from 14 species of defoliator.

At least one exotic parasitoid species, a European species not previously recorded in North America, was identified in this survey - Hormius radialis Telenga (Braconidae: Hormiinae) reared from a native defoliator, Choristoneura rosaceana, the oblique-banded leafroller.

Additionally, one apparent undescribed species was found in the reared material, a Charitopes n. sp. - D. Wahl det. (Ichneumonidae: Cryptinae: Phygadeuontini), reared from an indeterminable species of Yponomeutidae.

Results - Parasitoid Species Identified and Host Records

A complete listing of the parasitoid species identified in this project, including the number of host defoliator species each was reared from and the total number of rearing records for each species is presented in Table 1. Complete details for host species, rearing phenology, and collection information are available in print or electronic format from the authors. Parasitoid species reared from selected exotic defoliator species are presented in Table 2.

Table 1. Parasitoid species, classification, host and record numbers for parasitoids reared between 1994 and 1999.

Table 2. Defoliator host species, reared parasitoids, and number of rearing records compiled between 1994 and 1999.

In the interest of providing identification resources for pest control operators and others involved in managing the impacts from defoliating pests in the Pacific Northwest, graphic images of most of the more prominent parasitoid species listed in the preceding tables are provided in the subsequent portions of this report. (See image use and distribution note at end of document) Pictured species are those identified to the species level and/or were found to be parasitizing significant economic exotic species new to the region.

A summary of the records for defoliator larvae reared during CAPS surveys since 1994 is presented in Table 3. Note that the percent parasitism shown is provided for discussion purposes and is calculated relative to the number of total rearing records shown. For a few defoliator species the total number of rearing records shown is fairly inclusive, and the overall rate of parasitism (% Parasitism) approximates rates observed in the field (A. rosanus, C. pariana, and C. holmiana). However, for most species the total number of all larvae reared is not available, thus the parasitism rates shown are inflated to some degree and are not significant.

Project Background | Parasitoid Species and Host Records

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