Parasite Complex of the Larch Sawfly 1 in Minnesota 2

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Abstract
Only 2 parasites of the larch sawfly, Pristiphora erichsonii (Hartig), were found in all 16 study plots in northern Minnesota from 1970–72: the tachina fly Bessa harveyi (Townsend) averaged 30% parasitism over all plots; and the ichneumon Mesoleius tenthredinis Morley seldom exceeded 10% parasitism. Approximately 26% of the B. harveyi adults emerged in late-summer rather than the more beneficial spring emergence. Olesicampe benefactor Hinz, an ichneumon introduced into Minnesota in 1971 and 1972, was recovered from all 8 release plots. Parasitism reached 48% in one release plot, but was ca. 2% in other release plots by 1972. Dispersal into Minnesota, from releases in 1961 in Manitoba, was conspicuous by 1972 when O. benefactor was recovered from 5 of 8 check plots. Mesochorus dimidiatus Holmgren, an ichneumon hyperparasite of O. benefactor , was found in Minnesota for the 1st time.