Answer. Under ORS 90.100(21), a "hazard tree" is one that:
- Is located on a rented space in a manufactured dwelling park;
- Measures at least eight inches DBH; and
- Is considered, by an arborist licensed as a landscape construction professional pursuant to ORS 671.560 (Issuance of license) and certified by the International Society of Arboriculture, to pose an unreasonable risk of causing serious physical harm or damage to individuals or property in the near future.
Regarding hazard trees, ORS 90.727(3) (Maintenance of trees in rented spaces) provides that a landlord:
(a) Shall maintain a tree that is a hazard tree that was not planted by the current tenant, on a rented space in a manufactured dwelling park if the landlord knows or should know that the tree is a hazard tree. (Emphasis added.)
(b) May maintain a tree on the rented space to prevent the tree from becoming a hazard tree, after providing the tenant with reasonable written notice and a reasonable opportunity to maintain the tree; (Emphasis added.)
(c) Has discretion to decide whether the appropriate maintenance is removal or trimming of the hazard tree; and
(d) Is not responsible for maintaining a tree that is not a hazard tree or for maintaining any tree for aesthetic purposes.
ORS 90.727(5) provides as follows:
Except as provided in subsection (3) of this section, a tenant is responsible for maintaining the trees on the tenant's space in a manufactured dwelling park at the tenant's expense. (Emphasis added.)
So my take is that (a) if the trees qualify as hazard trees, the resident must maintain/remove them; (b) if the trees are technically not hazard trees (due to girth), the resident must still maintain them; and (c) if the resident declines to remove them, you should do so.
Given the recommendation of the arborist, you should contact the resident about having the trees removed at their expense. If the resident cannot afford the expense, you will have to work something out (e.g. cost sharing, or you remove them and seek reimbursement), since you cannot afford to allow this dangerous situation to continue, as it might endanger other residents.
ORS 90.740(4)(i) provides that it is the resident's responsibility to: "Maintain and water trees, including cleanup and removal of fallen branches and leaves, on the rented space for a manufactured dwelling except for hazard trees as provided in ORS 90.727." Thus, the resident's failure to do so in this case would constitute a basis for your issuance of a 30-day curable notice of termination under ORS 90.630(1).
If the resident declines to do the removal, and decides to move from the community, you will have to make sure that the buyer of the home is aware of the removal responsibility. You could write that into the new rental agreement. (If you do not make it a condition of the rental agreement, and they are "hazard trees," the new resident will not had a duty to remove - you will at your cost.) My guess is that with your advance notice to the prospective purchaser, the cost of removal would be deducted from the sales price.
As for your insurance agent's less than sage advice, I respectfully disagree. If a dangerous condition exists on a space in the community and it is not remedied, even though it is the tenant's primary responsibility, you will be held liable if you permit it to continue. It may be an "Act of God" in your agent's mind, but it is a foreseeable risk waiting to happen in the eyes of the law. (Henceforth, I promise not to give advice on insurance coverage, if your agent promises to refrain from practicing law.)
 "Diameter at breast height" i.e. 4.5 feet. See: http://www.phytosphere.com/treeord/measuringdbh.htm