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material for breeding. As with the European elm bark beetles, this wood does not have to be diseased. Eggs are laid in tunnels the adults excavate under the bark. Unlike those of the European species, these tunnels run across the wood grain. Grubs feed at right angles to the egg tunnels, producing characteristic galleries. Adutt beetles emerge in July and August and may fly to heatthy elms to feed on the bark of larger branches (4-10 inches in diameter). It is during this feeding phase that healthy trees can be inoculated with fungus spores. By late September the adutts seek locations on heatthy elms, near the ground, to spend the winter (figure 7). Under conditions of large popuiations and an abundance of elm breeding wood, approximately 1/3 ofthe native population is capable of starting a second generation that overwinters as larvae. Overwintering native larvae, like European larvae, are found in galleries under the barK of dead and dying elm material. Pupation occurs in the spring and adutt beetles emerge in June, fly to healthy elms to feed, and then find dead or dying material for breeding. Galleries are constructed, eggs are laid, and the resulting larvae produce an overwintering generation of adults. In southern Minnesota, where native and European beetles coexist, the native tends to be found in parks, woods, and along rivers, and less frequently on boulevard trees. In northern Minnesota, where native elm bark beetles predominate, they are found on boulevard trees as well as in wooded areas. MANAGEMENT The primary emphasis in a Dutch elm disease management program is preventative action. The basic elements are: 1. Detection. The systematic Inspection for Dutch elm disease of every elm in a control zone (that area defined by the community as a Dutch elm disease management area) and the detection of all dead elm wood, including firewood piles. 2. Isolation. The disruption of root grafts between infected and heatthy trees. 3. Removal. The prompt elimination of all dead and dying elm material from the control zone. 4. Disposal. The destruction (burning, burying, chipping, debarking) of elm material with intact bark. These measures, collectively called sanitation, are the key to successful management ofthe disease. They can significantly Iimtt the spread of the disease. Other managementtechniques include pruning of early infections, spraying insecticide, and injecting fungicide. Importance of Sanitation The purpose of sanitation is to remove elm bark beetle breeding sites and sources of the fungus, so as to limit the spread of the disease. Failure to employ sanitation measures will lead to higher beetle populations and more dead trees. The need for complete removal of dead and dying elms becomes apparent when one finds that a piece of elm branch the size of a small fireplace log, 22 x 4 inches, can prOduce up to 1,800 beetles. Left to stand, a complete tree could prOduce hundreds of thousands of beetles. If this tree is infested with the fungus, each emerging beetle carrying the fungus spores could then inoculate heallhy trees during feeding. However, early detection and proper tree disposal prevents ALL these beetles from spreading the disease. In addition to eliminating the beetle population, sannation also eliminates a potential reservoir for the disease. The fungus, intrOduced by contaminated beetles in the breeding phase, can become established in uninfected (nondiseased), nonliving elm woOd. Once infested, this otherwise disease-free material becomes a source for continued beetle spread of Dutch elm disease to healthy trees. 5