By Laura Jesse
Iowa State University Extension
My favorite part of the holidays has always been the Christmas tree. There is just something magical about bringing a real, live, fresh-cut evergreen tree into my living room and decorating it with pretty colored lights.
However, on occasion, a little more “real” world comes in than I bargain for. It is not uncommon to also bring in some insects or spiders that were on the tree while it was growing outdoors. Fortunately, these “accidental invader” insect and spider pests are harmless. Plus, if you have a budding entomologist in the house, insects are the best presents you can find under the tree!
Spiders and Aphids
The two pests most commonly found on fresh-cut trees are aphids and spiders. In both cases, adults that were on the trees back in late summer or fall laid eggs on the stems or foliage. These eggs would have remained dormant through the cold weather of winter, but you keep your house nice and warm and they think it is spring and hatch. Hopefully it is just a few, but occasionally several hundred baby insects or spiders can be on a single tree.
These newly hatched insects and spiderlings are very small (approximately 1/16th inch). Only when they are present in large numbers do they even make sufficient impact to be noticed. In many cases, the newly-hatched insects and spiders wander only a very short distance before drying out and dying.
One aphid that is most likely to hitchhike into the house in the egg stage is the white pine aphid. This is a relatively large aphid that feeds on sap from needles and stems of the eastern white pine. During the fall, females lay large, shiny black eggs end-to-end along the needles. Five to 25 eggs may line up like a row of oblong beads on a single needle. After several days at room temperature, these eggs begin to hatch into very, very small, dark gray to black aphids.
A similar situation occurs with several species of spiders. Eggs laid in a marble-sized, silken sac can hatch after several days indoors, and literally hundreds of very tiny, dark gray spiderlings may emerge in dense clusters.
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, whichever comes first. Similarly, spiders will not find adequate food for growth and development, so sadly they too will wander about for a brief period before they expire.
Aphids and spiders from Christmas trees are an annoyance because of their presence. But this does not justify use of any insecticides to combat their existence. Simply pick or vacuum them up and throw them away for the only necessary “control.”
Do not spray insecticides on fresh cut Christmas trees. There is almost no benefit, and while household insecticides are not a serious health threat, why expose your family to pesticides that aren’t needed?
The slight threat of a close encounter with these harmless, tiny “bugs” while you gather around the tree should not deter you from the tradition of using a live tree in your holiday decorations.As pest problems go, this is a minor annoyance at worst and shouldn’t keep anyone from enjoying a fresh-cut tree.
The Tick Hoax
A few years ago a popular radio personality recommended dusting your Christmas tree with “flea and tick powder” (the brand sold by his sponsor, by the way) as a prevention against ticks and the Lyme disease they may carry. This is an especially galling and nasty hoax playing on people’s fears of ticks (“blood suckers!”) and the highly publicized Lyme disease.
As we must remind often, there are no ticks in trees. Never. The widespread misconception that ticks live in trees appears to be deeply ingrained in the common folklore. There are no ticks in Christmas trees, nor in any other kind of tree.
Dusting your Christmas tree with “flea and tick powder” is a worthless misuse of pesticide that again, exposes your family to unnecessary pesticide residue with no possible benefit in return.
Spraying or dusting Christmas trees in not necessary. Period.
Laura Jesse, Plant Pathology, (515) 294-0589, firstname.lastname@example.org
Jean McGuire, Extension Communications and Marketing, (515) 294-7033, email@example.com