Focus on Spider Control: Spider-Man

Spiders, with a few exceptions, are innocuous pests, preferring to live their lives tucked away in the periphery of urban and suburban life. Most spiders remain unnoticed by a building’s occupants, only coming into focus when one decides to clean or a spider ventures out into the open running across a wall or the floor.

As do all arthropods, these fascinating arachnids live their lives for two purposes: to find food and to mate and pass along their genetic makeup. In accomplishing these two goals, spiders invariably invade our space — they cannot be avoided. This article will discuss how to minimize the presence of spiders both inside and out. The levels to which one might succeed depends on the surrounding environment — the habitat in which the building resides. For example, a home next to a lake or river is more likely to experience problems with web-building spiders than another house in the city surrounded by other buildings and concrete.

YOU CAN’T FIGHT THE WIND. Few people would associate air currents with spiders, but in the case of most web-building species, wind is important. Spiderlings climb up weed stems, shrubs, fences and other vertical objects to enact a process bred by instinct into every individual. At the top of the object, the spiderlings release a strand of silk that, when long enough, is caught up by the breeze and carries the spiderling off to its new life and home. Called ballooning, this act is how spiders disperse to new areas, areas where abundant food is hopefully available. Most spiderlings fail to survive the trip or end up in environments where they can’t find suitable web-building sites or food in the form of insects is lacking. Still, hundreds, possibly thousands, of spiderlings might bombard a home or other building over the course of the summer. If insects are abundant around such buildings, then more spiders survive and breed, thus resulting in a pest control issue for the building’s occupants.

TECHNIQUE #1: WHO TURNED OUT THE LIGHTS? A building located near a field or wooded area will likely serve as a landing pad for web-building spiderlings. Any right angle around the building will be suitable for web-building by spiders such as comb-footed spiders and orb-weavers. Sheet-web spiders and funnelweb (grass) spiders, as well as orb-weavers and some comb-footed species, will nest within vegetation and among piles of items located around a building.

Stopping the migration of these spiderlings to the building is impossible, but the numbers of spiders surviving and thriving may be reduced by limiting the presence of the insects on which they feed. In particular, such spiders rely on flying insects, especially the nighttime varieties. It is highly important, therefore, to control the lighting that attracts nighttime insects. It may be easy enough to convince homeowners to keep their outside lights turned off except when needed but in many cases, for security purposes, many homes and businesses need to have exterior nighttime lighting. Homeowners can be advised to switch to yellow "bug lite" bulbs while businesses should switch the fixtures on the building to low-pressure sodium vapor lamps, if possible. Location of bright lights, such as mercury vapor lamps, away from the building can draw insects from a structure’s vicinity. Such steps are important for those buildings located along lakes, ponds, rivers, creeks and fields where nighttime insects are abundant.

TECHNIQUE #2: HEY, WHERE’S MY HOUSE? Another contributing factor for the presence of spiders is abundant harborages. Chief among these is heavy ground covers, such as ivy and monkey grass (see photo at left). Such thick vegetation retains moisture and organic debris — two requisites for thriving insect populations. Minimizing thick ground cover, especially near the building, helps reduce the presence of wolf spiders and ground spiders — two types of spiders which are regular building invaders. Removal of piled items, such as lumber, rocks and bricks, eliminates potential harborages for all types of hunting spiders, brown recluse spiders and some web-builders, especially the comb-footed species, including the black widow. Indoors, in garages and basements, clutter reduction and organized storage practices minimize potential spider harborage sites.

TECHNIQUE #3: SWEEP 'EM OFF AND MOVE 'EM OUT. Because web-building spiderlings can’t be prevented from landing on a building, a regular schedule of spider web removal on the exterior can help keep such spiders to a minimum. Experience has demonstrated on countless residential homes that sweeping off spider webs using a broom or, better yet, a cobweb duster during every regular pest control service greatly reduces the numbers of web-building spiders and webbing on the outside of structures and within the garage. Although a few spiders will be present, frequent sweepings combined with changing of lighting brings the spider presence down to a level most customers can accept.

In cases where many web-building spiders are found, removal using a vacuum is beneficial because webs, spiders and egg sacs all are removed at the same time. During sweeping, spiders often aren’t killed and manage to drop to the ground where they can crawl back up and construct a new web. Treatment of corners and right angles where spider web-building is concentrated can further deter web-building.

TECHNIQUE #4: WE HEAR YOU KNOCKING BUT YOU CAN’T COME IN. Despite the best efforts involving the previously mentioned three techniques, some spiders will be found around every building and could manage to come inside. Sealing cracks and holes in exterior walls excludes spiders, especially hunting spiders, from entering. Keeping doors closed is important in screening out spiderlings floating on the breeze and adult spiders from wandering into the garage or through overhead doors. All foundation and attic vents should have tight-fitting insect screens. Although screens may not exclude the tiniest spiderlings, they will exclude many insects that spiderlings depend upon for food.

TECHNIQUE #5: SURE IS DRY IN HERE. Spiders thrive in moist or humid environments conducive to insect survival. Crawl spaces and attics with adequate ventilation have few spiders while those with little air movement may house dozens, if not hundreds, of spiders and their insect prey. Attics depend on a sufficient number of soffit vents and roof top vents to draw air through the soffits. Crawlspaces may have issues other than enough foundation vents, such as ground-to-floor clearance, standing water and drainage issues. Vapor barriers, pea gravel and sump pumps may be necessary for many crawl spaces to control moisture, thus making the space less hospitable for spiders.

SUMMARY. At least three of the five previously described techniques are necessary components of any structural insect control program. Minimizing insect populations through environmental methods is pivotal to controlling spiders around a structure. Ultimately, some treatment types may be necessary to resolve specific spider problems, especially where dangerous spider species are involved. By involving the customer to address the issues discussed here, the goal of a relatively spider-free home or building will be closer to reality.