Some diseases and pests of pines are native to the region while others are exotic (also known as introduced pests). A few examples of exotic pests include Grosmannia huntii, Bursaphelenchus xylophilus (Table 10.5) and Sirex noctilo.

On a global basis, more pines die from stress and subsequent beetle infection than die from diseases [11]. Landscape-scale beetle mortality has occurred after stresses in Belize, Canada, China, Germany, Nicaragua and the United States. Dendroctonus spp. and Ips spp. are considered to be the most destructive insects of pines in North America. The risk of injury from these pests increases with age and stocking. Overstocked stands result in stressed pines that emit volatile compounds that attract beetles. Another beetle that may cause problems is Monochamus spp.

In some regions, regeneration weevils do not exist and, therefore, pines are planted just after the harvesting operation. However, in the United States and parts of Europe a delay occurs between harvesting and planting. This delay reduces the risk of injury from certain weevils (e. g. Hylobiuspales). For a regime harvesting pines when 17-years old, a one year delay in planting reduces the amount of energy captured by about 5%.

In some cases, early growth rates have been increased by controlling certain insects. For example, reducing the level of weed competition can increase both the number of shoots per tree and the number of shoots that are affected by the insect Rhyacionia frustrana. Some believe that applying insecticides to pine plantations during the first two years will be economically beneficial (Table 10.6).

Nematodes (unsegmented roundworms) are present in nearly all forests but most soils in the southern hemisphere do not have species that are adapted to feed on pine roots. The growth of pine is affected by the stubby-root nematode (Trichodorus christiei) and the lance nematode (Hoplolaimus galeatus). Some nematodes (Bursaphelencus spp.) can kill pines when they are planted as exotics.

Numerous fungi can affect the growth of pines. The most common disease of pines in the United States is Cronartium fusiforme f. sp. fusiforme, which can affect the stems and branches of several pines. In a few stands, over half of the trees are infected with this fungus.