The Other Guys

Features - WOOD-DESTROYING PESTS

One PMP solves several obscure mysteries of wood-eating insects.

Subscribe
October 18, 2021

Granary weevil (Sitophilus granarius)
Bugwood.org

In my 20 years in the industry, I have been involved with many cases involving wood-eating insects. The majority involved termites or LABO (Lyctinae, Anobiinae, Bostrichidae, old house borer) wood-infesting beetles. Then there are a few insects that damage wood but do not consume it, such as carpenter bees and carpenter ants. They simply use wood as a nesting medium. (Like us.) Once these nests are abandoned, secondary pests move in, giving the impression that they are the ones causing damage.

Giant resin bees (Megachile sculpturalis) are known to displace carpenter bees from their holes and build their own nests inside them. They can look similar to a carpenter bee to someone who has not studied them, and they will push out the old debris left behind by the previous tenants, giving the appearance that they are causing damage. Acrobat ants (Crematogaster spp.) also are known to occupy wood members previously damaged by termites, carpenter ants, beetles or wood decay, and they too will clean out debris from galleries and drop it in piles. The homeowners, and even some PMPs, may see this behavior and assume that carpenter ants are the culprit. Looking closely at the debris they drop in piles will tell you otherwise. Bits and pieces of dead acrobat ants will be mixed in with it, rather than parts of carpenter ants. Seeing this will change your control strategy.

Another example of misidentifying a wood-eating culprit is finding large beetle larvae occupying severely rotten wood. I’ve had samples of different scarab beetle larvae sent to me that were dug out of a rotten garage door frame or piece of wood siding buried under mulch, with the question of what kind of wood borer it is and what to do for treatment. In these cases, treatment was simple. Replace the rotten wood and correct the conditions that caused it to get that way. Some stored product pests also can superficially damage wood when their larvae bore into it near the infested food source to pupate. Cockroaches can cause damage to wooden items in severe infestations where food is limited. They are survivors and will attempt to get nutrients from anything they can. Remember, they share an ancestor with termites.

We are all familiar with the common wood-destroying beetles that are known to damage and reinfest wood in structures. However, there are some outliers that you may not be familiar with. These are “the other guys.” They include insects like wharf borers, telephone pole beetles and wood-boring weevils. You may have seen them in your NPMA Field Guide, the Mallis Handbook of Pest Control or some other reference book. You may have even heard mention of these from a presenter at your state conference. But have you ever dealt with them? Perhaps you have, but just didn’t know it.

SOAKING SPRINKLER. So far in my career, I have seen two cases of wood-boring weevil infestations. Both occurred in slab homes near Charleston, S.C. In the first case, a PMP contacted me and said a customer’s kitchen cabinets were being destroyed by something, and there were several weevils present. At first, having not dealt with these before, I thought the weevils he was seeing were incidental. Probably, there was some stored product that was infested with rice or granary weevils nearby. He sent some samples to me, and sure enough, they had the anatomical features to be wood-boring weevils as outlined in the NPMA Field Guide.

After reading up on their behavior, life cycle and control recommendations, I made a trip to visit the account. The PMP was not wrong. A section of the kitchen cabinets was being absolutely destroyed and reduced to a very fine powder, with sections of the wood crumbling in my hands when touched. According to the literature I read, wood-boring weevils only infest wood with a very high moisture content. So, I pulled out my trusty moisture meter and began poking around. The strange thing is, even though it was dry and powdery to the touch, the infested wood had very high moisture readings. The wall next to the cabinet also had high readings. As I moved the meter further from that point, the readings dropped dramatically. This told me that something was supplying the water needed to keep this area wet for a long period of time. In this section of the kitchen cabinet, there were no plumbing lines. All plumbing lines for the sink and dishwasher were located on the other wall and away from the damaged area.

As we were scratching our heads trying to figure out what the source of the moisture could be, in a stroke of luck, the customer’s sprinkler system in the yard turned on. Then we heard a strange rustling noise coming from the outside wall directly behind the kitchen cabinet. We looked outside, and lo and behold, a sprinkler head was facing the wrong direction and dousing that side of the house with water. There you go. The solution: fix the sprinkler head, allow the area to dry, then replace the damaged cabinet.

Flat oak borer (Smodicum cucujiforme)
Robert Webster / xpda.com / CC-BY-SA-4.0

The second case occurred several years later. A customer found damage to her hardwood floors next to an exterior wall in the bedroom. Weevils were collected and identified, and I headed down again with my moisture meter in hand. Sure enough, there were high levels of moisture in the infested area. Remembering the first case, I asked about a sprinkler system, but they did not have one. We inspected the outside wall where the inside damage was occurring and noticed a large mud hole next to the foundation. The customer said every time it rained, water collected there, and there had been lots of rain recently. Similar solution: fix the grading issue, let it dry out, replace the damaged wood.

A WHAT? Sometimes, you run into something way out in left field and it becomes an interesting learning experience. A homeowner noticed damage and holes appearing in the hardwood floors of her newly built home near Hilton Head Island, S.C. The pest management professional contacted me saying the damage was very similar to that done by an old house borer, but the emerging beetles did not look anything like them. He sent me samples, and at first, I was stumped. They looked a bit like wharf borers, but with some different features.

Digging further, I identified them as flat oak borers (Smodicum cucujiforme) and had it confirmed by Clemson University. What the heck is a flat oak borer? Apparently, it is another species of longhorn beetle (Cerambycidae) that infests wood. Doing some research, I learned that not much is known about them. There was conflicting information about whether or not they actually reinfest seasoned wood. I presented the homeowner with the information I found and some treatment recommendations. I also suggested she contact her builder, since this was occurring in a newly built home, to see if they could do anything. Last I heard, she was involved in a lawsuit with the builder.

CONCLUSION. Running across unusual situations makes things interesting and is part of the job that I love. It also reinforces the notion that identification is important, especially if something feels different about the situation. Don’t forget, sometimes it is “the other guys.”

The author is technical director at Terminix Service, Columbia, S.C.