[Occassional Invaders] Alien Attack?

Ants, cockroaches and termites might make up the bread and butter of the average PCO’s work, but what about those other infrequent but annoying pests that undoubtedly also show up? These occasional invaders, as they are called, come in numerous types and varieties, and treating them effectively requires a sharp eye on the part of PCOs. The catch is, since PCOs don’t regularly come across these pests, they may find control to be surprisingly challenging.

The key to stopping occasional invaders, says Dr. Eric Benson, professor and extension entomologist at Clemson University, Clemson, S.C., is proper identification. Benson answers most all of the questions that come in from both consumers and PCOs regarding pests. He also co-hosts a popular radio call-in show on South Carolina Educational Radio called "Got Bugs?" When it comes to occasional invaders, Benson says, PCOs can be easily deceived.

"A lot of these pests that cause callbacks that are a problem I would say fall into the occasional invader spot because you don’t see them that often," Benson said. Because of this, he noted, gaining control can be challenging. It’s not uncommon, for example, for PCOs to mistake plaster beetles for pantry pests. However, control measures for these two pests differ greatly.

Simple laws of nature determine where occasional invaders end up, says Benson. "In theory, every creature…should be able to get anywhere," he says. If an insect can’t get to a certain location, it simply can’t get there, it can’t survive there, or when it does get there, it changes into something else.

PCOs need to consider the first two cases when controlling occasional pests, Benson says. However, many PCOs only concern themselves with preventing the invader’s survival once it gets inside. But, Benson says, that’s missing out on the most important factor. "I would say first and foremost, which we overlook a lot when we’re just treating, is you want to try to prevent the critter…from getting there in the first place," he said.

In addition, Benson says, knowing the species is absolutely critical to successful occasional invader control. By correctly identifying the pests, PCOs can be virtually certain that their treatments will end up in the right location. "If you don’t know the species, you don’t know the location, you don’t know where to treat," Benson said. Regardless of the product used, he says, "if you don’t put it in the right spot for the pests, you’re not going to get them, and that’s where we fall short a lot of times with occasional invaders."

Benson defines occasional invaders as a catch-all group of pests that invade structures, and he further divides the group into three major categories: incidental pests, seasonal pests, and minor pests. The incidental pests include such invaders as earwigs that just happen to wander in to a structure, but won’t establish there. Seasonal pests are those such as Asian lady beetles, which can become problematic at certain times of the year. And minor pests, such as plaster beetles, can become established in structures, possibly becoming problematic, especially in commercial accounts. The following is a rundown of some of the occasional invaders that Benson deals with regularly.

INCIDENTAL PESTS. There are many different incidental occasional invaders, Benson notes, and their presence is often related to moisture. However, the recommended control measures for these pests are, for the most part, minimal.

Topping the list in this category are pillbugs, sowbugs and scuds. These crustaceans all need moist environments to live. Therefore, they find ideal living conditions under excessive mulch, near decaying vegetation, and in damp basements or crawlspaces, Benson said.

The key to controlling these pests is finding and removing moisture sources. That, in addition to customer education about the pests and removing those that have entered should be all that is necessary. Chemical measures aren’t needed because these pests won’t typically survive indoors anyway. "Why spend a lot of time spraying when they’re going to die anyway," he notes. "What you want to do is stop them before they get in."

Two other groups of incidental pests that tend to like thick mulched or organic moist areas are springtails and earwigs. Again, exclusion, habitat alteration, moisture reduction and mechanical removal of the pests are the keys to control. "Maybe, in a rare occasion, if it’s really bad, you could do some insecticidal treatments of mulch outside, as long as you can penetrate the mulch or roll it back," he notes.

Millipedes, and in particular garden millipedes, are another common invader. These pests can grow to large numbers in yards, Benson explained, and they gain access to a structure via cracks and crevices under doors and thresholds. "They don’t have designs on going into the house," Benson said. "The problem is there’s just so many of them." Millipedes reach structures basically by accident, via their normal crawling behavior, although they will trail each other, Benson notes. "Again, not another critter I think you need to spray when it gets bad," Benson said. However, he added, because these pests do tend to have a bad odor, they should be swept or vacuumed up as soon as possible.

Benson added that it can be difficult to achieve chemical control of millipedes in outdoor areas, simply because many treatments don’t fully penetrate the mulch to reach them. "Other than that it is basically letting them ride out the season," he said. "They will eventually crash out. They’ll outstrip their resources and in the wintertime they should be knocked back."

Centipedes, although not as frustrating to control, tend to cause more alarm among homeowners. Unlike millipedes, centipedes are fast-moving, predatory creatures that can bite. While millipedes have two legs per body segment, centipedes have just one. Also, while millipedes survive off of organic vegetation, centipedes feed on other insects. "So if you have centipedes then you have plenty of insects around," Benson notes.

There are two main types of centipedes: the house centipede, an indoor pest, and the outdoor centipedes that come in under thresholds. Perimeter treatments may help to control the outdoor species. For indoor species, crack and crevice dust treatments or limited spraying may help, but mechanical control measures may be all that’s needed. Benson notes house centipedes aren’t typically found in great numbers. "They are the mountain lions of the insect world inside that house, so there can’t be that many of them," he said. However, if a structure has a large number of house centipedes, that would indicate a problematic entry point allowing other insects access to the structure.

Scorpions are another predatory occasional pest, however, most species are not dangerous. These pests can gain access to structures under doors and through garages. However, Benson said they can also come from the attic down. Sticky traps may help to pinpoint entry points, and perimeter treatments may help to control those scorpions that are entering from the outside.

Benson also characterizes some spider species as occasional invaders. He refers to these species as "ambush" spiders, such as wolf spiders, that simply wander in under doors. No chemical controls are needed for these types of pests. "A lot of the spiders, in my mind, especially the ground dwelling ones," he says, "are only incidental pests."

Crickets can also be characterized as incidental, and possibly seasonal, invaders, Benson says. There are two main types: field crickets and house crickets. The field cricket is a black, stout-bodied cricket that is not known to establish indoors. Exclusion is the best remedy, Benson said. If you perform any treatment, it would be outside. Meanwhile the house cricket, which is brown, can occasionally establish indoors, Benson notes, in such places as crawlspaces, basements and damp garages. Being closely related to cockroaches, house crickets can be controlled with well-placed cockroach gel baits.

SEASONAL AND MINOR PESTS. These days, the "mother of all seasonal invaders," as Benson refers to it, is the multi-colored Asian lady beetle. This beetle originated in Asia, and its spread is believed to be related to organized releases of the pest during the 1970s and 80s to control aphids. Today the beetle is widespread east of the Mississippi. It has become especially problematic during the fall when the beetles enter structures in great numbers in search of overwintering sites. Problems with these pests can become serious in such locations as doctors’ and dentists’ offices, Benson said.

While it looks much like your average ladybug, says Benson, this isn’t the species most of us have grown up with. One identifying characteristic is an M-shaped marking on their pronotum. "This species aggregates in huge numbers," Benson noted. "It can really overwhelm a structure."

Research indicates the multi-colored Asian lady beetle prefers older homes, which have more cracks and crevices to serve as overwintering sites. They also like to aggregate in higher locations, which means they prefer two-story houses. The beetles can bite if provoked, have a foul odor and can stain when crushed. Control methods include exclusion, caulking and sealing. Vacuuming works well to remove them, and insecticide treatments may be used if necessary in certain accounts. Benson said proactive treatments on exterior areas of a structure, particularly window frames, door frames and soffit areas, may help prevent them from gaining access.

A new seasonal pest that appears to be a growing problem is the marmorated stink bug. Discovered in Pennsylvania in 2001, this pest has begun to spread through the region. "They’re not a problem as far as a structure goes but they aggregate in huge numbers just like lady beetles," Benson said.

Boxelder bugs are also a problem in the fall, when these pests begin looking for overwintering sites. They feed on boxelder trees and silver maples. Control methods can be mechanical removal or spot treatments around entry points. Successful control also might involve a little sleuthing around the structure in question, Benson notes. "I would go out and find the boxelder [trees] or the maples and then start looking for the most logical, obvious cracks and crevices that they could come into for their overwintering sites."

Another common overwintering pest is the cluster fly, not to be confused with the house fly or the blow fly. Exclusion is the best control remedy. "Basically you want to try to prevent them from where they’re entering," he said, explaining that’s often high up on buildings. Benson also said that spraying the flies once they’re indoors can create secondary dermestid beetle problems if the dead flies aren’t removed.

Considered by Benson to be minor pests, mold and plaster beetles can be a problem in new building construction, especially where rainy weather has repeatedly dampened construction materials, leading to the growth of mold within wall voids. These beetles, which feed on mold spores, can then get into the structure and become established. Since their presence might go unnoticed for long periods of time, populations get huge. Then when a PCO is finally called in, many times the beetles are mistaken for pantry pests. Control will only be achieved, he notes, if the moisture condition is corrected, the structure dries out on its own, or the mold is knocked down with a borate.

SEEING IS BELIEVING. Pinpointing suspected occasional invader problems also means considering other causes, Benson points out. "Not only do you have to know what it is, you may also have to know what it is not," he said. This brings up the issue of parasitosis, which Benson said he encounters on a regular basis. Individuals with this condition believe that pests are biting them, but none can be found. In most cases, Benson says, there is an explanation for the irritation, however it’s not pests. Just a few common causes are allergies, dry skin and static electricity. Benson recommends that when parasitosis is suspected, PCOs should remain open-minded. "You could have an organism you’re just not seeing," he said. "Send them in, get them identified, because maybe there’s something there." As with all other areas of pest control, he adds, proper identification is key. "If something is biting people, disturbing people, you should be able to catch it and see it," Benson explained.

For best results against occasional invaders, says Benson, PCOs should try to categorize problems as either incidental, seasonal or minor. Doing this will help determine the proper treatment regimen. "You can’t do a whole lot about incidentals," he said. When it comes to seasonal and minor pests, a good rule of thumb is to consider what the pest is likely to do. "Try to do everything you can to make sure it can’t get there in the first place," he said. If you can’t do that, he added, "try to make sure it can’t survive there."

Editor’s note: Dr. Eric Benson can be reached at ebenson@clemson.edu.

The author is a frequent contributor to PCT magazine. She can be reached via e-mail at lmckenna@giemedia.com.