It is because of Oak Wilt.
Here in MN, we do not touch oaks trees in the spring (April, May and June), because the oak wilt fungus is highly active at this time. Any injury made to an oak during these months can be a potential entrance point for the fungus carried by the picnic beetle. Once you get into July, Aug, and Sept the risk is lower but it is standard practice here to only prune oaks during dormancy.
I will start pruning Oaks for my clients no sooner than mid October and will prune right thru until April 1st.
So this does put a bit of a crimp on the availabilty of trees to use for such events like TCC during the spring. A few years back we held our first fall event and it was a treat to be able to compete in huge Oaks.
Now if we dont have a TCC this fall, we'll be forced to have one in spring if we want to send a rep to the Internationals next summer.
Ive always said we should have one in January (just once), competing in the TCC when it maybe 5 degrees outside /forum/images/graemlins/grin.gif thats how you seperate the men from the boys /forum/images/graemlins/grin.gif I doubt it will ever happen though /forum/images/graemlins/smirk.gif