. Dutch elm disease in Illinois. Fungicides; Scolytus multistriatus; Hylurgopinus rufipes; Dutch elm disease. 10 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 53 rier of the fungus, feeds mainly in crotches of 1- and 2-year-old twigs (Fig. 8). The fungus spores (Fig. 9), deposited in the feeding wounds (Fig. 10), grow and spread in the vessels of the young sapwood. In- fection occurs mainly in May and early June, when the springwood vessels are adjacent to or near the inner surface of the bark. In time the leaves on branches invaded by the fungus wilt and the branches die. In Illinois there are two
. Dutch elm disease in Illinois. Fungicides; Scolytus multistriatus; Hylurgopinus rufipes; Dutch elm disease. 10 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 53 rier of the fungus, feeds mainly in crotches of 1- and 2-year-old twigs (Fig. 8). The fungus spores (Fig. 9), deposited in the feeding wounds (Fig. 10), grow and spread in the vessels of the young sapwood. In- fection occurs mainly in May and early June, when the springwood vessels are adjacent to or near the inner surface of the bark. In time the leaves on branches invaded by the fungus wilt and the branches die. In Illinois there are two broods of the smaller European elm bark beetle each year. The first brood of adult beetles (which have overwintered as larvae in elm bark) starts emerging in May and con- tinues to emerge until mid-July. Emerging beetles make small holes in the bark (Fig. 11). Peak emergence of this brood occurs in mid- June. The second brood, which develops in 5-7 weeks from eggs laid. Fig. 7.—Adult of the smaller Eu- ropean elm bark beetle. It is shiny, dark reddish brown, and about one- eighth inch long. ^:^f^:. Fig. 8.—Close-up of a bark beetle feeding in the crotch of a young shoot. Spores of the Dutch elm disease fungus adhere to the body of this Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Carter, J. Cedric (James Cedric), 1905-; Illinois. Natural History Survey Division. [Urbana]
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