I am puzzled

[M.Green - SVTS]

Hello All,

I am sure everyone has seen a pine with a witches broom or maybe 10 or 20 witches brooms on it going all the way to the top. I learned when I was younger that it was a parasite that caused the pine to grow like that.

Can someone give me that parasites name, or list a few parasites that could possible cause the tree to grow in that way?

Thank you in advance.

 

[S Mc]

Dwarf mistletoe Arceuthobium, Viscaceae, is a parasite that affects pines in many areas including Newfoundland to southern Alaska which I would think could hit Maine, and throughout the coniferous forests of the West. (This according to Sinclair's Diseases of Trees and Shrubs.

Out here, in Montana, the pines affected with witches brooming are more often caused by the fungus Elytroderma deformans.



Sylvia

 

[groundsmgr]

Hello All,

I am sure everyone has seen a pine with a witches broom or maybe 10 or 20 witches brooms on it going all the way to the top. I learned when I was younger that it was a parasite that caused the pine to grow like that.

Can someone give me that parasites name, or list a few parasites that could possible cause the tree to grow in that way?

Thank you in advance.

It has been a while since i read anything on witches brrom, but I thought it was more of a disease lit rust or fungi.

 

[S Mc]

Witches brooming is more a description of a reaction than the disease itself. It can be caused by parasites, fungi, insects and herbicides.

Sylvia

 

[M.Green - SVTS]

Witches brooming is more a description of a reaction than the disease itself. It can be caused by parasites, fungi, insects and herbicides.

Sylvia

Yeah I knew that part. I knew witches broom wasn't the correct term for it but it's the term I use to describe it. I want to become more familiar with what is actually happening inside the tree that is causing the effect.

Thanks for the information, if any can be added that would be great also!

 

[S Mc]

Remembering that the definition of "witches' broom" is: "Proliferation of many shoots near the end of a branch in response to the death of the terminal bud." As defined in Costello's Abiotic Disorders of Landscape Plants, A diagnostic Guide helps explain the reaction of a tree due to insect damage and pathogens.

However a couple of direct quotes from Sinclair's book are:

Pg 446:

"Most species [dwarf mistletoe] also induce witches' brooms. Brooms are of two types, called systemic if the endophytic system keeps pace with apical growth of the branch, resulting in systemic infection within the broom; or nonsytemic if the endophytic system remains concentrated near the original site of infection. Aerial shoots develop along the branches of systemically infected brooms, but grow only near the original site of infection on nonsystemic brooms."

In describing witches' brooms created by fungi such as in Prunus sp., pg 6:

"Brooms are induced by perennial intercellular mycelium in twigs. Whether the fungus grows through petioles to stems or infects them directly is unclear. Once in a stem, however, Taphrina wiesneri causes localized swelling and twig proliferation that may continue for several years."

Sylvia