A system was developed to produce large numbers (30 × 106 per week) of Trichogramma minutum Riley on eggs of the Angoumois grain moth, Sitotroga cerealella (Olivier). The parasitized host eggs were packaged and shipped in bulk for release against the spruce budworm, Choristoneura fumiferana (Clemens), and several other lepidopterous pests. Initial attempts to use the Mediterranean flour moth, Ephestia kuehniella (Zeller), as a host failed due to such factors as infestation by mites and parasitoids, low fecundity, long generation time, and the necessity for large labour inputs during moth collection. Eggs of S. cerealella, used to rear the host, remained viable when stored for up to 1 month at 9 °C, but eggs stored at 2 °C remained acceptable for parasitism for only 15 days. Rearing the host at high humidity (> 70% RH) gave better percentage emergence and infestation of grain than rearing at low humidity (< 30% RH). Developmental rates of T. minutum were determined over a range of temperatures and the developmental threshold and heat unit accumulations necessary for complete development were calculated. Using these values, Trichogramma were programmed, during the latter stages of production, to emerge within 24 h of exposure to light at room temperature. The programming facilitated shipment and handling of the parasitoids prior to their release.

Two systems for releasing the egg parasitoid, Trichogramma minutum Riley, from ground level in forest stands are described: (1) a gridded point-source release using parasitized host eggs attached to cards, and (2) a hand-held leafblower distributing parasitized eggs in bulk. Neither technique affected the emergence of the parasitoids released. Parasitoids emerging from eggs released in bulk had a similar sex ratio, longevity, and fecundity to those not released. Both methods of ground release achieved uniform parasitoid distribution and resulted in levels of parasitism similar to those achieved with aerial releases. Parasitism was greater in the mid- to upper canopy of trees than in the lower canopy. The difficulties associated with each technique and its comparative usefulness in experimental and operational programs are discussed.

An aerial dispersal system was developed for inundative release of insect eggs, Anagasta kuehniella (Zeller) and Sitotroga cerealella (Olivier), parasitized by Trichogramma minutum Riley. The equipment was used successfully in field tests over a 4-year period (1982–1985) in a coniferous plantation forest near Hearst, Ont. The release equipment consisted of simple electrical components, mechanical components from a small grain planter, and a centrifugal slinger used for aerial seeding of jack pine. The equipment was mounted on a Bell® 47 helicopter, flown at about 25 m above the ground. A swath width of 15 m was attained using this system. Application rates ranged from 12.3 to 263.0 g ♀ ♀ parasitoids per hectare (0.6–25 × 106 ♀ ♀ parasitoids per hectare) during the 4 years of tests.

The egg parasitoid, Trichogramma minutum Riley, was distributed by helicopter over forest stands near Hearst, Ont., to control the spruce budworm, Choristoneura fumiferana (Clemens). The quality of the parasitoids in terms of emergence, proportion of females, longevity, and fecundity was not affected by aerial release. Based on monitoring with deposit cards, at 10 m above ground, the helicopter had an effective swath width of ca. 10 m. Aerial release provided an uneven distribution of deposit on 1.0-ha plots, with significantly less parasitized material reaching the outer edges of each plot than in the centre; parasitism of sentinel egg masses within the plots corresponded to the distribution of deposit. Over 50% of the released material was deposited on the ground. Drift outside the plots was generally less than 25 m, never exceeding 100 m. The extent of drift was dependent on the application technique, and to a lesser extent, wind direction. Deposit cards provided an extensive rather than an intensive sampling method for monitoring the aerial distribution of T. minutum.

The ability of the egg parasitoid, Trichogramma minutum Riley, to suppress outbreak populations of the spruce budworm, Choristoneura fumiferana (Clemens), was studied annually near Hearst, Ont., from 1982 through 1986. Timing of broadcast parasitoid-releases was linked to spruce budworm moth emergence and oviposition. These phenological relationships were predicted from a regression based on larval development at least 2 weeks before expected emergence; this allowed sufficient time to regulate (program) parasitoid emergence during mass-rearing. Emergence of caged spruce budworm adults was used to monitor moth eclosion in the field. Pheromone traps provided daily information on the activity of male moths and helped to synchronize the parasitoid releases with spruce budworm oviposition. Information on parasitoid activity was obtained from sentinel (laboratory-reared) and naturally occurring spruce budworm egg masses. A curvilinear relationship between the rate of parasitoid release and parasitism of sentinel egg masses was developed. Two parasitoid releases, 1 week apart, early in the oviposition period of spruce budworm, significantly increased parasitism of host eggs by 14–83% and reduced larval populations correspondingly from 42 to 82%. Single releases were less effective and increased parasitism by 0.3–52% (single ground release, 1986). Two parasitoid releases, combined with a spring application of Bacillus thuringiensis Berliner to larval populations, was the most effective strategy and resulted in 83% egg parasitism and 93% larval reduction. Release rates greater than 12–16 × 106 ♀ ♀ T. minutum per hectare were not warranted based on impact and costs. The effects of release timing, weather, host density, and parasitoid quality on the future successful use of T. minutum are discussed.