Field isolates of threeTrichogrammaspecies were collected and tested in the laboratory for host acceptance and suitability of oblique-banded leafroller (Choristoneura rosaceana(Harris) (OBLR) andEphestia kuehniellaZeller eggs. An isolate ofTrichogramma minutumRiley that was collected from OBLR eggs found on birch trees in Ontario had a much higher level of acceptance of OBLR eggs than any of the other strains that were tested. Two isolates ofTrichogrammasp. nr.pretiosumRiley, and four isolates ofTrichogramma sibericumSorokina, were collected from leafroller and cutworm eggs found in commercial raspberry and blueberry fields in British Columbia. All of these isolates and an additional isolate ofT. sibericum,originally collected from blackheaded fireworm on cranberries, accepted and successfully parasitized OBLR eggs, but at a very low level. In contrast, all eightTrichogrammaisolates had a high level of acceptance of the rearing hostE. kuehniella.All isolates ofT. sibericumappear to be completely thelytokous. Thelytokous isolates reverted to sexual reproduction on treatment with tetracycline indicating that thelytoky was caused by microorganisms.
