Scott, Walter E. (ed.) / Wisconsin Academy review
Vol. 3, No. 4 (Fall 1956)
Chambers, E. L.
The Dutch elm disease in Wisconsin, pp. 148-149
Fall. 1956 149 larger number of samples were screened out as showing no evidence of the- brown discoloration characteristic of the disease making culturing unnecessary. The principal vector of the Dutch elm di- sease is the smaller European elm bark beetle (Scolytus multistriatus). This is one of our introduced pests and was first re- ported in the East in 1904, and it was not until 1952 that it was found in Wisconsin. First reported from Milwaukee County, annual surveys made by the State Entomologist's Office reveal it to be present in 19 southeastern counties as of September 1956, the farth- est north being reported at Fond du Lao and Green Lake Counties. This beetle appears to confine its attack to elm, showing preference for breeding in recently cut, brok- en, or dying elm but feeds upon the healthy trees and be- cause of this habit spreads the Dutch elm disease when the adults emerge from infected elm wood where they become con- taminated with and carry the spores of the disease. On the healthy trees, the work of the beetle can be detected by the feeding scarsin the crotches of the small- er twigs. Evidence of attack on dead or dying elm trees or parts thereof is the small round emergence holes made by the adults, often the bark of such trees appearing as though hit by "bird shot." Examination of the wood beneath the bark of such an infested tree will reveal a characteristic pattern of tunnels. The female makes a vertical tunnel following the grain of the wood about two inches long in which she lays her eggs, and the larvae upon hatching cut similar tunnels at right angles to the original one. There are two generations each year. The native elm bark beetle gHylurgopinus ruipes ) is also of importance as a carrier of this disease, and in some areas of other states it is still the only carrier present. The Wisconsin Department of Agriculture *has been able to obtain excellent cooperation :s S from all of the municipalities where this di- sease has been found. Diseased trees are be- ing removed, burned promptly, and the area within 1,000 feet sprayed with DDT and sanita- tion practices carried out. All efforts of '- Hi m control must be directed toward the beetles and elimination of their breeding places. Elm material can be destroyed by burning or by turn- ing and wetting all bark surfaces with a 1% emulsion of DDT. Where elm is the most logical tree to use, it may still be planted if some provision is made for its protection against the Dutch elm disease. # # # Fall. 19 56 149
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