Studies of the Lecanium Scale, Eulecanium coryli (L.), and its Parasite, Blastothrix sericea (Dalm.), in British Columbia

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Abstract
The lecanium scale was introduced into Vancouver with nursery stock from England in 1903, and by 1910 had become firmly established. Severe injury to broad-leaved maple, vine maple and horse chestnut was reported in 1923, and chemical control operations were undertaken from 1924 to 1930, but with very transitory effects (9, 10). The encyrtid wasp, Blastothrix sericea (Dalm.), imported from England in 1928 and 1929, quickly became established at the liberation points in Sorth Vancouver, and by June, 1930 had dispersed over an area of about 20 square miles. In April, 1931, twigs with parasitized scales from North Vancouver were distributed at intervals throughout the main area of lecanium infestation south and east of Vancouver, and by June of that year the parasite was known to be established over an area of about 100 square miles. By 1932, the percentage of parasitism in the mature lecanium females reached 90 to 100 per cent, and host population density was at very low levels (12, 13).

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