Posted by: Jessica Wong, Master Gardener Coordinator, Broomfield County Extension
Spiders may be one of the most important and abundant biological control agents in our gardens. They are generalist predators that feed almost exclusively on arthropods, including many we consider pests. Spiders will kill as many as 50 times the number of prey they actually eat. And, relax, they are not at all interested in biting humans.
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| This female wolf spider (Tigrosa helluo) was recently brought into our office by a Broomfield employee. She was about 3 inches long! I released her into our Xeriscape Demonstration Garden where, I'm sure, she is providing effective pest control. Photo credit: Jessica Wong |
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| Dysdera crocata, commonly known as sowbug killer, woodlouse hunter, and “roly-poly killer.” Photo credit: iNaturalist.org |
Spiders provide pest control, day and night, on the ground, on all above-ground parts of a plant, and even in the air. Wolf spiders (Lycosidae) are excellent hunters of pests on the ground, including ants, earwigs, and caterpillars and grubs found at the soil surface. Sowbug killers (Dysdera crocata) are another ground hunting spider that prey on, you guessed it, sowbugs and pillbugs.
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| This spider is aptly named bold jumper Phidippus audax. Photo credit: Jessica Wong |
Jumping spiders (Salticidae) are small hunters can be found in a variety of habitats, from tree trunks to leaves to under rocks. These small spiders hunt for small prey like mosquitoes, aphids, and midges. Crab spiders (Thomisidae) are ambush predators that can be found waiting for prey on flowers. Orbweavers (Araneidae) are the spiders that spin the familiar vertical webs with concentric rings. They catch anything that flies by, such as winged aphids, wasps, and moths.
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| Goldenrod crab spiders Misumena vatia can change from white to yellow and back to white for better camouflage. Photo credit: Charley Eiseman, Ohio State University Extension |
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| Banded orb weaver Argiope trifasciata. Photo credit: David Cappaert, Michigan State University, Bugwood.org |
Spiders can provide the most effective pest control when there are many species present in your garden. To support spiders in your garden you will need to provide habitats for them. Apply a layer of mulch or leaf litter for the ground spiders. Reduce tilling to prevent the disturbance of spider nests and burrows. Intercrop varying height plants to create microclimates and web anchor points. Diversifying your landscape can increase the diversity and abundance of spiders in your garden, which will increase the potential for pest control. By creating abundant habitat for spiders in your garden you will also make it more attractive for them to stay outside rather than come inside your house.
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| Various groups of spiders occupy different parts of a tree. Figure from Patrick Marc & Alain Canard 1997 “Maintaining spider biodiversity in agroecosystems as a tool in pest control.” Agriculture, Ecosystems and Environment 62:229-235. |
I love spiders. Spiders are always welcomed in my garden. I don’t even mind them in my house since they are doing a great job of killing flies and ants. I don’t expect you to love spiders now too, but I hope you at least have a greater appreciation for them in your garden.