October 10, 2009

1 - Juniper mistletoe is difficult to eradicate.

Yard and Garden October 10, 2009


I recently searched the web for information about mistletoe growing on junipers around our home in Placitas. My question is about the genus and what to do about it. In a quick search on the web I found a suspect, Phoradendron juniperinum, which according to what I understand is not as destructive as "dwarf mistletoe."

Here is what I found about mistletoe on pines in Colorado and wonder if it covers our situation as well; Colorado State Univ. Extension.

"...Witches brooms develop over many years. Dwarf mistletoe witches brooms extract nutrients and water from uninfected parts of the tree, gradually reducing host tree vigor and eventually causing premature death. Junipers infested with juniper mistletoe will have clusters of the yellowish green parasitic plant growing amongst the juniper foliage (Figure 6).

"Juniper mistletoe witches brooms extract only water from the host plant. On heavily infested trees, the parasite can cause death of portions of the tree during prolonged periods of below normal precipitation...

"...The fruits and seeds of Phoradendron juniperinum are spread by birds and consequently can be spread great distances in a single season. A number of bird species feed on the juniper mistletoe fruits and disperse the seeds by excreting or regurgitating them. Seeds are deposited on the top side of branches of juniper hosts. Germinating seeds produce a holdfast that penetrates the host plant...."


The information you have is accurate. I contacted Stephani Sandoval, NMSU Extension Forest Health Specialist to confirm this information and the information I had. She said, Mistletoe on juniper is true mistletoe not to be confused with dwarf mistletoe. This is a parasitic plant (not a fungus) and that you may prolong the life of the tree by pruning infested branches but it does not necessarily cure it. Also if the trunk of the tree is infested or a branch within 6 inches of the trunk this tree would be a good candidate for removal.

Dwarf mistletoe is found in pines while this mistletoe infests junipers as its name implies. Other factors to consider are that eradication is difficult to impossible. Often our best actions are preventing the spread of this mistletoe (by birds) by removing fruiting stems (manually or with ethephon spray). However removing the stems does not kill the mistletoe.

You can remove the most heavily infested plants and in the case of lightly infested plants, prune infested branches if the mistletoe is at least 6 inches from the trunk, otherwise remove the tree completely. Of course you can remove only the fruiting branches to prevent spread as described above. However, when you remove the branch within about 6 inches of the point of attachment of the mistletoe, it will sprout again from the parts left inside the juniper branch.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.


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