2004-08-25 WS & CC Meeting - Laserfiche WebLink

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Sanitation Timetable All dead and dying elm wood from the previous year must be properly disposed of prior to April 1 since adult native elm bark beetles can become active on this date. This also guarantees destruction of overwintered larvae of both the European and native elm bark beetles prior to their June emergence (figures 6 and 7). Figure 6. Life cycle of European elm bark beetle. Overwintering larvae Active adults Overwintering larvae Jan May June Sept Oct Nov Dee *H-Adults from high-risk trees US-Adults from slow-wilting trees Figure 7. Ufe cycle of native elm bark beetle Overwintering adults Active adults Dee Jan Mar ~r May June 'Under certain conditions (high beetle populations, abundant brood wood) native elm bark beetles can overwinter as larvae, which then emerge as active adults the following year by June 1. Overwintering larvae I Detection of dead and dying elm trees in early June is the next essential step in thesanttation program. Delays caused by attempts to posttively detect the presence of the fungus could reduce the effectiveness of the program, by allowing time for infested beetles to emerge. Regardless of the cause of death, the tree is a potential breeding site for contaminated beetles. Once detected, dead and dying elm trees should be promptly isolated as necessary, removed, and destroyed. However, the epidemic proportion of the disease in many areas creates removal and disposal difficulties that require the wisest and most effective use of resources. These communities will need to concentrate initial efforts on trees which pose the greatest threat and then on trees which are a less serious threat. High-risk trees are those which have severe or rapid wilt after spring leafing, for they are capable of producing a second generation of European adults by July 15. It is imperative that high-risk trees be removed and disposed of by July 15. Removal by July 15 will also be effective against the native elm bark beetle, which can be found on dead or dying elms until that date. Removal after July 15 will be ineffective against the native, since tt is no longer to be found on dead or dying trees. Slow-wiiting trees do not become a hazard until late in the summer, but by then the water-conducting vessels have become smaller and thus are less susceptible tothe disease. In sanitation programs with limited resources, slow-witting trees and trees detected later should be removed as soon as possible over the remainder of the year (prior to April of the following year). It is important to understand that delays in tree removal and disposal can permit beetle population increases and impair disease management. Therefore, every communtty should constantly strive for prompt removal and disposal of all dead and dying elms. For those communities without resources for immediate removal and disposal, selective removal and disposal of high-risk trees will produce the best results. Disposal Disposal of diseased elms is the final important step in a successful sanitation program. The goal is to destroy the beetles and to eliminate their breeding sites. Burning and burying are the most effective means of disposal but are not productive from the standpoint of wood utilization. Chipping is a good alternative 6