The chanterelle, a type of wild mushroom, grows
beneath host trees such as the Douglas fir, which
provide it with necessary sugars. The underground
filaments of chanterelles, which extract the sugars,
in turn provide nutrients and water for their hosts.
Because of this mutually beneficial relationship,
harvesting the chanterelles growing beneath a
Douglas fir seriously endangers the tree.

Which of the following, if true, casts the most doubt
on the conclusion drawn above?
(A) The number of wild mushrooms harvested has
increased in recent years.
(B) Chanterelles grow not only beneath Douglas firs
but also beneath other host trees.
(C) Many types of wild mushrooms are found only
in forests and cannot easily be grown
elsewhere.
(D) The harvesting of wild mushrooms stimulates
future growth of those mushrooms.
(E) Young Douglas fir seedlings die without the
nutrients and water provided by chanterelle
filaments.

I suppose, option (E) would be the correct choice, but according to the answer sheet (D) has been proffered over (E)
Please help me to understand.