We have a Christmas Tree Farm in Montgomery County. Lately we have had a big...
We have a Christmas Tree Farm in Montgomery County. Lately we have had a big problem with pine oak gall on Scotch Pine. Can you cut the galls off? In some cases the tree needs to be removed. I wondered how effective removal of the gall was without cutting down the tree.
Thank you for your question to eXtension.
According to this Minnesota publication (http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/pine-oak-and-pine-pine-gall-rusts/ ), this gall is caused by a fungal rust disease. As with most rust diseases, control is very difficult, and Minnesota suggests pretty much ignoring it in landscape situations. Clemson Univ. in S. Carolina also does not recommend controls: http://www.clemson.edu/extension/hgic/pests/plant_pests/trees/hgic2008.html .
Penn State offers some more suggestions, but doesn't list specific fungicides: http://extension.psu.edu/pests/ipm/agriculture/christmas-tree/pest-fact-sheets/shoot-and-branch-inju...
The US Forest Service recommends removing trees identified with having the gall: http://www.na.fs.fed.us/spfo/pubs/howtos/ht_stemrusts/ht_stemrusts.htm
An article from Michigan State (http://treedoctor.anr.msu.edu/Feb12_GallRustofPines.pdf ) recommends trying to find and remove nearby oak trees, which are the alternate host for this rust disease. Generally, I've found that removing alternate hosts doesn't work well for other rust diseases, like cedar-apple rust...the spores blow too far for this to be effective.
I hope this helps.