Littleleaf of pine, caused by _Phytophthora cinnamomi_, is the most
serious disease of shortleaf pine in the Piedmont region of the South.
Loblolly is also affected, usually where associated with infected
shortleaf pine. The disease is most evident in older age classes, rarely
attacking stands under 20 years old.
[Illustration: Needle symptoms and damage of littleleaf on shortleaf
pine.]
[Illustration: (cont.)]
The disease is caused by a malfunctioning of the root system due to a
combination of biological and physical factors. A fungus, _Phytophthora
cinnamomi_ attacks and kills the root tips. When conditions of moisture,
fertility, and drainage are adverse, they reduce tree vigor and prevent
the tree from rapidly replacing the destroyed root tips. Trees on good
sites are reportedly also attacked by the fungus, but their vigor is
such that they quickly overcome the disease by producing new root tips.
The disease usually progresses rather slowly. Some trees may persist
fifteen or more years after the appearance of initial symptoms. In
general, trees live only five or six years after attack, but they may
die in as little as one year. Symptoms are those typical of trees in
stress due to a malfunction of the root system. In the early stage of
the disease the foliage may turn yellow-green and the current year’s
needles are shorter than normal. Later stages of the disease are
sparsely foliated crowns with short needles (reduced from three to five
to only one-half to three inches in length) and dead branches. Abundant
foliage sprouting on the hole of infected shortleaf is common.
Losses are minimized by salvage cuttings and by favoring loblolly and
hardwoods in regeneration plans.