[IUFRO RG 7.02 FORPATH] Melampsorella brooms on NY fraser fir Christmas trees

Nancy, The problem is that it takes several years to produce a broom of a size that results in culling, and hence the current culls are almost certainly a legacy from before the time of chick weed control. The broom in your picture is at least five years old. So, even if chickweed control is effective, it will take several more years before the damage disappears. Infection by basidiospores occurs in the spring from telia on dead foliage of the previous year, and the first symptom is a slight swelling of the infected twig a year or more later. Two years after infection the first systemically infected shoots appear. Assuming that chickweed control became effective in 2007, then 2007 was the last possible year of infection (from telia on 2006 chickweed foliage). The first systemically infected shoots on these infections would have been produced in 2009. They would be nearly impossible to find this late in the year, but they should be visible early summer 2010 when the aecia on their new shoots are in their full glory. But there is a further consideration. Rusts of this sort typically have wave years of infection. I would expect that the large majority of brooms in a single plantation belong to a single or at most a few age cohorts. This means that you may have to wait several years before you can begin to be confident that the chickweed control has worked (or that other hosts are involved). Bart van der Kamp UBC