Carpenter ants – What are Carpenters doing in my garden?
By Gregory Covello, A.C.E.
While tending your garden you notice large black ants. You tell yourself that these ants can’t be Carpenter Ants, because Carpenter Ants eat wood, not my garden. However you notice these large ants crawling on plants and they seem to be interested in vegetable leaves. What’s going? You have Carpenter Ants.
How much wood does a Carpenter Ant eat?
While some people may still be trying to figure out how much wood a woodchuck can chuck, I would like to answer the question “How much wood does a Carpenter Ant eat?” The answer: None. Carpenter Ants are commonly referred to as carpenters due to their ability to chew wood, not their ability to eat it. Carpenter Ants (Camponotus species) will chew through wood to hollow it out in an attempt to create a nesting site. The galleries that these ants create in wood appear smooth as if sanded down with sandpaper by a carpenter. The neat work of the Camponotus ant contributed to its common name, the Carpenter Ant.
Why are they on my plants?
Now we know that these large ants don’t eat wood, so what are they eating? Why are they in my garden? Why are they on my plants? Honeydew. I’m not referring to the melon here; I am referring to the secretion. Honeydew is a sweet sticky secretion that is primarily made by aphids, however can come from other plant pests such as whiteflies as well. This honeydew supplies the Carpenter Ants with the carbohydrates that they crave and is most likely the reason that you have these ants in your garden.
There is another possible reason as to why these ants may be calling your garden their own. Carpenter ants will hollow out lumber, firewood, stumps, trees and other wood. If you are utilizing railroad ties or other lumber to construct raised beds, you may want to consider a close inspection. As noted earlier, Camponotus chew wood. As they excavate their galleries, the ants carry the chewed wood (often referred to as frass) to an open area. Often this excavated sawdust is dropped into a pile. Piles of unexplained sawdust near your lumber may now have an explanation; you have an active Carpenter Ant situation.
An active Carpenter Ant situation in your garden in itself is not necessarily bad however it may be an indication of other issues. If you notice what appears to be large ant (or any ant for that matter) resting on a leaf, you may want to take a closer look. Ants like honeydew. Their craving for honeydew has created a symbiotic relationship with the aphids that produce the honeydew. Therefor what may appear to be an ant resting on a leaf may actually be ant protecting some aphids. Check the underside of the leaves of your plants. You may need a magnifying lens, as aphids are very small. Aphids will damage and potentially destroy your plants, so the presence of Carpenter Ants on your plants may have actually helped you identify a real problem in your garden.
After conducting a thorough inspection, treatment should be considered. If the ant infestation is limited to plants only, consider treating the underlying problem: the aphids. If you identified sawdust and damage to wood you may want to consider treating the areas where the damage was noted with an appropriate pesticide (read the label before choosing or using the product). There are a variety of products on the market to help you achieve your treatment goal. Low impact products containing diatomaceous earth may help solve low-level situations. Another simple solution may be removing the infested wood (bedding lumber, firewood, that old wooden shed you have been meaning to demolish, etc.) If nests are located in firewood you should probably consider burning that wood outdoors (fire pits, chimineas, etc.). Do not bring infested wood indoors as doing so may risk infesting your home. Severe situations such as damaged trees and the presence of Carpenter Ants indoors may require a professional inspection and/or treatment.
Gregory Covello, ACE is an Associate Certified Entomologist and District Manager for Viking Pest Control based out of Warren, Somerset County. He is a back yard gardener and hobbyist bee keeper. He can be reached at 973-296-6523 or firstname.lastname@example.org.