Christmas trees are vulnerable to dozens of different pests. Many times these pests are dormant in the cold weather or their eggs are present and when the tree is brought into a warm structure the dormant insects become active and the eggs begin to hatch. The insects then become a nuisance when they are seen crawling on the tree and the presents underneath. Most of the pests are small and may only be visible in large numbers. Aphids are common pests of evergreen trees, and the warm conditions of the home may cause overwintering aphid eggs to hatch. Cinara aphids are large brown, or almost black aphids that resemble small swollen ticks (ticks, by the way, are almost never found on Christmas trees). These aphids do not bite or spread diseases and they will not feed on regular house plants.
Some trees may contain adelgids, which produce cottony secretions over their bodies. The tree may look quite festive since the adelgids resemble a dusting of snow. Spider mites also inhabit Christmas trees. They appear as tiny red and brown dots when shaken out of the tree and they produce very fine webbing. They can create small red stains on carpets, ornaments, or furnishings. Spider mites only feed on the tree and quickly die after the tree is cut. Larger Christmas tree insects include beetles and praying mantids. Adult mantids will be long gone from the cold temperatures, but mantid egg cases can hatch when introduced to the warmth of the home and there may be hundreds of tiny mantids wandering in search of food. Christmas trees often harbor various species of non-threatening spiders as well.
None of the insects or spiders that emerge after being carried in on a fresh-cut tree will cause any harm or damage to the tree, the house, the furnishings or the occupants. They cannot bite or sting and they will not live long enough to grow or multiply. Low levels of sap in the tree mean an inadequate food supply for aphids and other sap-sucking insects. They will quickly die of starvation or desiccation (dry out), whichever comes first. Similarly, spiders will not find adequate food for growth and development, so they too will wander about for a brief period before they expire. Dead and live insects can be removed with a vacuum cleaner. Do not spray Christmas trees with pesticides, as they may do more harm than the insects themselves.