Pressure could be applied by petitioning the committee. If a substantial fraction of the residents request it, it would be hard to ignore.
Alternatively, you could put a motion to a general meeting by which the OC would resolve to maintain its common property trees by annual pruning. Make sure you give notice to get it on the agenda well before your next general meeting and have someone to second the motion. Provide a supporting statement to accompany the motion explaining that it used to be done annually and why that is necessary. Resist the temptation to include blatant criticisms of the current SC. It will be obvious enough that you are implying that they have been slack. If the OC resolves to do something, then the SC is compelled to act on that.
You might want to include funding in your motion. Eg. Motion: That the owners corporation resolves to engage an arborist to undertake form pruning of the trees adjacent to the building on an annual basis to prevent them from contacting the building and to maintain views from and ventilation and light into the units, and that the proposed budget and levies for 2020-21 be increased by $X to fund this work.