With the Christmas season coming there is nothing better than the fresh smell of pine needles. But when you bring a tree home, you might also be bringing some diverse hitch-hiking insects on it.
Pine and fir trees grown for the purpose of being used as Christmas trees are vulnerable to a wide range of pests, weeds and diseases. Some infestations, like that of the Balsam woolly adelgid might even lead to death. Pre-harvested trees are also vulnerable to fungal pathogens.
Even larger animals, such as mammals, also pose a threat to harvests and are considered pests. Among these are deer, gophers and ground squirrels which damage roots and buds. In addition, some species of birds are considered pests as well, like the Pine Grosbeak – a bird which feeds on conifer buds.
- Balsam woolly adelgid (Adelges piceae) is the biggest threat to the Christmas tree industry. It can cause huge cosmetic damage to the tree, which is of great importance for the customer. The Balsam woolly adelgids are small soft-bodied insects which usually infest firs. White, woolly spots on the tree are how these insects appear and if left untreated consequences can be fatal.
- Balsam twig aphids (Mindarus abietnus) are another type of common tree pests, affecting fir and spruce trees in spring season. Heavily infested trees’ growth is stunted, causing losses to the industry. Other species of adelgids like the pine bark adelgid, the Cooley spruce gall adelgid and the Eastern spruce gall adelgid also attack fir trees.
- Bagworms (family Psychidae) are another serious pest. These insects are able to defoliate a tree completely if they are large in numbers. More so, the damage their silk causes can last for years.
- Pine shoot beetles (Tomicus piniperda) and gypsy moths (Lymantria dispar) are an invasive pest species which also threaten Christmas trees. In Canada, infestations of gypsy moths reached such large scales that the government assigned moth eradication programs.
- Four major types of conifers are cultivated for the use as Christmas trees – pines, Douglas-firs, true firs and spruce trees. All of them are vulnerable to different types of insect pests. Douglas-firs are most vulnerable to the Cooley spruce gall adelgid. The true firs are vulnerable to insects like the Balsam gall midge and the Balsam twig aphid. Spruce trees are most susceptible to White pine weevils, Cooley spruce gall adelgid and Pine needle scales. Finally, pines face infestations from Pine root collar weevils, Zimmerman pine moths, pine needle scales and white pine weevils.
Reforestation fields and Christmas tree plantations often suffer from the significant destruction caused by small mammals. Conifer plantation seedlings suffer damages from voles (Myodes glareolus) or meadow mice (Microtus pennsylvanicus). Especially when sites are on old pasture where there is a lot of grass and undergrowth. Losses of importance are caused by the pocket gopher (family Geomyidae), which attacks root systems as well as strips the bark off the base of conifer seedlings. Other common mammal pest of these trees are porcupines, rabbits, deer and the thirteen-lined ground squirrel.
Arachnids are pests which infect tree populations, such species are spruce spider mites (Oligonychus ununguis) and rust mites (Nalepella).
Christmas tree farmers also consider birds to be another species of animals that are pests to the industry. Examples of such birds are the Pine Grosbeak (Pinicola enucleator) and the Yellow-bellied Sapsucker (Sphyrapicus varius). The Pine Grosbeak diet includes the buds on conifers, including Christmas trees. Such damage causes deformations, stunts tree growth and thins the foliage. The Yellow-bellied Sapsucker generally attacks Scots and Austrian pine trees. The sapsucker bird pecks holes in sapling bark, causing the sap to bleed out, thus killing the tree and inviting insects and pathogens to develop.
However, Christmas tree pests need a special environment and adequate food to survive. Therefore, you do not have to worry about them infesting your property. Soon after moving indoors most Christmas tree insects die out completely due to insufficient humidity and loss of habitat.