Beneficial Bugs: Spiders

(Updated: June 23, 2021)

I’m always excited to see spiders around because they tell me the environment is healthy. Spiders are what’s called an indicator species, similar to frogs, in that they happen to be very sensitive to pesticides and environmental toxins.

Indicator Species

Many species (plants included!) can be useful signposts to us about the quality of the environment. Example: the reason canaries were present in cages in coal mines was to give the miners a warning if toxic gasses were present in the shaft. If the birds died, workers evacuated the mine.

Birds are very sensitive to toxins and can die from gasses emitted from cooking with non-stick cookware or toxin buildup of pesticides that are commonplace in our lives now. Rachel Carson’s book Silent Spring warned us back in 1962 of the damages of unrestricted spraying. 

The Case against the -Cides

I don’t use pesticides, herbicides, or any kind of biocide, even natural ones. The use of both synthetic and natural pesticides eliminates not only the “pest” populations. Often these pesticides are non-specific and wipe out all insect life indiscriminately, including beneficial pollinators, such as butterflies and honeybees. These -cides also harm the natural predators of the “pest” species, such as many species of birds and bats, that are also highly important to a healthy ecosystem.

Consistent and preventative use of pesticides allows the “pest” to evolve faster than the control, leading to genetic resistance in pest populations. This causes a cyclical pattern where more and more pesticides must be used for control while the pests are simultaneously growing resistant to them. Coincidentally this is the same reason antibiotic resistance has become so widespread. But that’s a topic for another time.

Since our previous homestead was slightly upwind of a conventional farm, seeing abundant spiders, egg sacs, and webs meant our property was not suffering contamination from pesticide drift. This was especially important to me because that farm sprayed using a small single-propeller plane. If the spiders had ever disappeared, I would’ve known there was a problem.

Spiders and Balance

Spiders are also an indication that the ecosystem is stable and in balance. When the “pest” populations are out of control, that means there is something out of balance. Heavy pest pressures link to mono-cropped (meaning only 1 species of plant) fields. Many of these fields are thousands of uninterrupted acres or kilometers of a single crop, like wheat. Imagine, discovering an all-you-can-eat buffet that stretches as far as the eye can see. You’ll begin to understand the problem.

However, diversely cropped areas that emulate Nature give proper environments to multiple species of animals, including the natural predators of each “pest” population, encouraging a healthy balance. Not to mention the many options of companion plants to grow alongside your crops that naturally repel certain species. Some examples are marigold [Tagetes sp.], lavender [Lavendula officinalis], lemongrass [Cymbopogon citratus], and peppermint [Mentha x piperita].

“Pests” Have Purpose Too

Something we often overlook is that pests serve a critical purpose in the web of life. They can serve as population control by being predators of weak, sick, or over-fertilized plants. All are states of imbalance, two of insufficiency and the other of forced over-abundance, neither of which are healthy. Healthy and well-nourished plants are often able to resist pest pressures without succumbing. 

Spiders Welcome

Spiders act as a predator to “pest” insects like mosquitoes. They are also prey for larger wildlife like songbirds. Because of this, spiders are often welcome to be present on organic farms or gardens that use Integrated Pest Management (IPM). If they are present, that means a healthy balanced ecosystem exists for other types of wildlife as well. 

So next time you see spiders in the garden, don’t run in fear or grab something to kill them. Welcome them as our friends and helpers!

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