Spider egg sacs represent a concentrated future infestation, as a single sac can hold hundreds of developing spiderlings. Finding these silken nurseries attached to the exterior of a home, shed, or deck signals the need for prompt action. The risk of hundreds of tiny spiders emerging makes timely and effective eradication a priority for maintaining a comfortable outdoor environment. This guide provides practical methods for safely eliminating existing spider sacs and modifying the surrounding habitat to prevent future egg-laying activity.
Identifying Outdoor Spider Egg Sacs
Spider egg sacs are typically constructed from silk, but their appearance varies widely depending on the species. Most sacs are spherical or oval, ranging in size from a few millimeters up to two centimeters in diameter, roughly the size of a pea to a quarter. Freshly laid sacs often appear white, cream, or pale yellow, though they may turn tan or brown as they age or weather. The texture of the silk covering can be smooth, fuzzy, papery, or spiky, which often helps distinguish between different spider types. Female spiders place these sacs in protected, sheltered locations outside, such as under eaves, attached to window frames, deep within dense foliage, or tucked into the corners of sheds and garages. Some species, such as wolf spiders, carry their egg sac attached to their spinnerets, while others like orb weavers suspend them within their webs.
Immediate Physical Removal Methods
The most direct and reliable way to eliminate an existing egg sac is through physical destruction and safe disposal. If the sac is located on a solid, easily accessible surface like a patio floor or a step, it can be crushed using a hard object, such as a shoe or a brick, ensuring the contents are fully destroyed. When dealing with sacs in hard-to-reach or elevated areas, a vacuum cleaner equipped with a long hose attachment is often the best approach.
Vacuuming the sac instantly removes it, along with any surrounding webbing and the adult spider if present. The vacuum bag or canister contents must be disposed of immediately outside the home, as the silk sac provides protection that may allow the eggs or newly hatched spiderlings to survive the suction. For bag vacuums, place the sealed bag into a lidded outdoor trash bin. For bagless models, empty the contents into a sealable plastic bag, seal it tightly, and then discard the bag to ensure containment. If the sac belongs to a potentially venomous species, freezing the sealed bag for several hours before final disposal can neutralize the contents.
For sacs on walls or ceilings, a stiff brush or a putty knife can be used to scrape the sac directly into a wide-mouthed container or plastic bag. Avoid squeezing the sac during this process, as this could cause spiderlings to burst out. Once contained, the bag or container should be sealed immediately and then destroyed, either by crushing or placing it in an outdoor trash receptacle. High-pressure water from a garden hose can dislodge sacs from structures, but this method rarely results in the destruction of the sac itself, requiring a follow-up step to neutralize the eggs.
Using Sprays and Residual Treatments
Chemical and non-chemical applications can serve as both a direct method of destruction and a residual treatment for future hatchlings. Contact insecticidal sprays specifically labeled for spiders or their eggs should be applied directly to the sac to penetrate the silk and kill the contents. Since the silk is tightly woven and water-resistant, oil-based pesticides are generally more effective than water-based formulas because they more easily compromise the sac’s protective layer.
For sacs found on or near plants, horticultural oil or insecticidal soap offers a less toxic treatment option. These oils work by physically coating the sac, penetrating the egg’s soft outer shell, and disrupting cellular development, preventing hatching. The application must be thorough to ensure the entire sac is covered, leading to suffocation and death of the eggs.
Diatomaceous earth (DE) provides a non-chemical residual defense against spiderlings that manage to hatch or migrate into the area. This fine, powdery substance is made from the fossilized remains of diatoms, which are microscopic, sharp-edged particles. When spiderlings crawl over the dust, the particles abrade their outer waxy layer, causing them to lose moisture and dehydrate. Applying a thin, barely visible layer of food-grade DE into cracks, crevices, and along foundations can help manage new spider activity.
Long-Term Habitat Modification
Preventing spiders from laying new egg sacs requires modifying the outdoor environment to make it less hospitable. Spiders are drawn to areas that offer shelter and a plentiful food source, so reducing clutter is the first step. Removing wood piles, old pots, excess debris, and dense vegetation near the house eliminates preferred nesting and hiding spots. Trimming back shrubs, vines, and tree branches so they do not touch the structure limits the pathways spiders use to access protected areas like eaves and window frames.
Managing exterior lighting also plays a significant role in reducing spider populations. White and blue-toned lights attract flying insects, which are the primary food source for outdoor spiders. Switching to yellow, amber, or warm-colored LED bulbs (2700K or lower) is recommended because these longer wavelengths are less visible to insects. Finally, sealing any gaps, cracks, and entry points into sheds, garages, and the foundation of the home denies spiders the protected, dark corners they seek out for laying their egg sacs.