Scores of trees will be chopped down on Tuesday after contracting a bacterial canker.
The 200 black hybrid poplar trees at Rushcliffe Country Park near Ruddington in Nottinghamshire are less than 15 years old but are already dying.
The problem was discovered after rangers noticed a number of trees were shedding branches, possibly caused by waterlogged ground.
The work is expected to last up to two weeks.
The trees form part of a nature trail opened last year.
Rushcliffe Borough Council spokesman Rick Simpkin said: "The trees are tall and there is a risk of someone getting hurt by a falling branch or even a tree blowing over if the wind gets up too much.
"Sadly there is no option other than to close this part of Gibbies Wood while we cut the trees down.
"Poplar trees grow very fast. At this time of year they are of course heavy with leaves, but the bases are not strong enough - the disease is killing them and the risk of injury is too great."
The trees' timber will be used in the park - some will be left on site to benefit wildlife with the rest wood chipped for path surfaces, made into fuel or used on small construction projects.