I'm not an expert, but I've been successfully planting trees since early childhood and love every minute of it. What type of insect is it that causes the galls on my Pin Oaks? I started 2 years ago pruning off the infected branches and burning them, now this year there are considerably less galls (my Oaks are about 15-20 feet now, I started them from 12" saplings.) Plus now I've got about 15 Pin Oaks I started from acorns that I've got to get rid of soon.

Reply to post by CMiller, on March 25, 2000 at 17:31:40:

C.M.
To verify exactly what type of insect is contributing to your oak gall problem- find out what type of gall you are dealing with. If you have an Agricultural Experiment Station available they may be able to help identify the insect- usually a mite or gall midge. The Horned Oak gall is quite common on oaks in general, but rarely are the galls detrimental to the trees. It's more of an aesthetic issue.
Some chemicals have been tried, like Sevin and Mauget B, but the adults are out anywhere from may 1st to July 31. Pretty big window.
As you have been doing, pruning out infected branches will help but depending on your state, timing of the insect would also help.
Kim

Reply to post by Kim, on March 25, 2000 at 17:31:40:

The following site may be of interest. It is quite informative re: galls and insects.
http://www.vsv.slu.se/johnb/insects/gallmake.htm

Reply to post by Kim, on March 25, 2000 at 17:31:40:

I have a 24 inch pin oak in a mulched bed in my back yard with a few dozen horned oak galls on it. Across the street, my neighbor has one the same size, but which has been partly mangled by past utility crews; more recent work has improved significantly, but the tree has only half the crown mine has. It is severely infested… thousands of galls.
I wonder if this insect might be opportunistic?

Reply to post by Ed Milhous, on March 25, 2000 at 20:49:03:

Statement at the following site would seem to confirm the point of view that tree condition as well as other aspects of resistance are factors in gall insect attraction to individual plants.
http://hammock.ifas.ufl.edu/en/galls_s.html

Reply to post by Ed Milhous, on March 25, 2000 at 20:49:03:

I was recently on a university campus in the northeast where a parkinglot has been planted with pin oak, perhaps 75 trees established 15 years ago. By quick estimation, half of them were covered by horned oak galls and the other half fully untouched. They were all planted in medians under approximately the same conditions.

Reply to post by Wayne, on March 27, 2000 at 09:44:29:

Wayne, do you suppose the plant source (genetic inheritance) may have been different for the trees?
Were the trees affected grouped or scattered among the unaffected trees?
Could there have been differences in underlying soil or in irrigation?
Were there any other signs of stress in the trees that might be associated with the galls?

Reply to post by Kim, on March 25, 2000 at 17:31:40:

Kim, about 20 years ago we had quite good results with Mauget injections of Bidrin. (I have no idea if it's currently labeled for the pest in CT). It prevented new gall formation on a reasonably infested tree. End of first season there was a "halo" of clean, new twig growth all over the tree. By end of second season the older galls were drying out and the expanding twigs "popped" them off, resulting in a nearly clean tree. I can't tell you how the tree has fared since.

Reply to post by Mark Goodwin, on March 29, 2000 at 08:58:05:

Mark,

Its quite possible that the trees came from several nurseries. To provide as many as were in this lot would stretch the ability of the local nurserymen and so I would guess they were bought in from who knows where. The soils before construction on this site would have been a sandy-loam with a ph of about 5 to 5.5 with good drainage; after construction it was most likely some combination of original soil, cement, and a coating of "topsoil" about 6 inches deep.

The effected trees were scattered all over the lot which was what caught my attention. I parked in a space between one that was loaded and one that was totally clean. In this lot there is no irrigation system at all and although the campus has a nicely developed arboretum I dont believe there is a watering program for the parking lot trees at all. Given the last several summers we have had here, stress across the board could be expected but some may be worse off than others I suppose.

It appears that the galls have been on the effected trees for years. there are galls of differing sizes and apparent ages (guessing).


Wayne