Pest Alert: Uninvited Holiday Guests
Date: December 20, 2012
From: Steve Frank, Extension Entomologist
Uninvited Holiday Guests: Part 1
Christmas trees like other crops have many pests that feed on them. Also like other crops, they are grown outside. Thus, many insect species may be unfortunate enough to stop for a rest just as the tree is bundled up and trucked to your local box store. Every year people report arthropods that have hitchhiked into their house on a Christmas tree. Here are a few of the most common.
Cinara sp. aphids feed on Christmas trees and are sometimes present at harvest time (https://www.freshfromflorida.com/content/download/63248/1446784/PEST_ALERT_Aphids_on_Christmas_Trees_2015.pdf). These critters feed on tree sap and are often mistaken for ticks once inside a house. They are easily distinguished from ticks because they have 6 legs whereas ticks have 8. In addition they are round whereas ticks are flat. These aphids cannot survive long without a living tree and will soon fizzle out as the tree dries.
Spruce spider mites are another Christmas tree pest that could come in on your tree. You would have to be looking very hard to see these guys. They are very small.
Cooley spruce gall adelgids are Christmas tree pests and super interesting. They have a complex life cycle in which they alternate between two hosts. The produce galls that look like cones that actually contain hundreds of young aphids.
It is important to remember that all of these pests feed on live trees. The will not set up shop under your couch or on your dog. As the tree dies so will they. If there are more than you can handle then return the tree and pick a new one. It is very unlikely you would get another infested tree even from the same dealer.
Uninvited Holiday Guests: Part 2
We discussed arthropod pests of Christmas trees that people find once they bring trees into their home. In this article we will discuss arthropod hitchhikers that do not feed on Christmas trees but were unlucky enough to be on one when it was cut, bundled, and shipped. When you get home with your tree these critters may wander off and startle the kids or amuse your cat but will not cause harm to people or become permanent residents of your home. They do not want to be there any more (probably way less) than you want them there.
Many arthropods spend the winter as eggs that their parents laid in the fall. The eggs typically hatch when warm weather comes in the spring. However, if the eggs are on a tree that you place in front of your warm yuletide fire they will hatch (please don’t put your Christmas tree near a fire, yuletide or otherwise).
Spiders frequently lay eggs on trees and hitchhike into homes on Christmas trees. Spider hatchlings get around in nature by climbing to the top of plants and ballooning on silk threads. Essentially they get blown around and hope to land in a good spot. In your living room there is probably not much wind (though Grandpa always complains about the draft) but they will still string silk around the tree as they try to catch a breeze. Eventually they will give up and crawl off the tree where you might spot them on the wall.
Praying mantids are a fun insect to rear. The egg case looks like brown foam from which hundreds of small mantids emerge. The young mantids are an inch or so long and very quick. They climb all over and really freak people out who aren’t expecting them. Young mantids are hungry, voracious predators so maybe they will eat the other bugs you didn’t know you had. A lot of bugs live in your home no matter how clean it is. Our friends at http://www.yourwildlife.org can tell you all about this.
People also report adult and larval lady beetles or green lacewings. Of course people often find Asian multicolored lady beetles in their house that come in through vents and cracks to spend the winter. It is possible that adult or larval lady beetles of other species could be hunkered down for the winter on your Christmas tree along with green lacewings and their larvae. Green lacewings are beautiful delicate insects as adults and predators as larvae. They are very cool to watch and to feed if you happen to have some other bugs lying around.
As we mentioned, Christmas trees are a natural product grown outdoors. Any insect that happened to land on a tree and get bundled up will emerge in your living room. Other things we have found include bark beetles, psyllids, stinkbugs, weevils, and moths. Just vacuum them up. It is very unlikely any human pest, like ticks, or structural pest, like termites, would ever get transported on Christmas trees. So don’t worry. Watch the cat go crazy and enjoy the wildlife.