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Spiders

Also known as Araneae, Jumping spiders, Wolf spiders, Crab spiders, Orb weavers

Beneficial or harmlessBeneficial
A jumping spider (Carrhotus viduus) photographed in Laos Photo: Basile Morin · CC BY-SA 4.0

In short

All spiders are predators, and they are often the most important natural control of garden pests. Most are generalists that eat almost any insect of a suitable size, including beetles, caterpillars, leafhoppers and aphids. Spider control is rarely needed.

How it looks

Two main body parts, eight legs, no antennae and usually six or eight eyes. Sizes range from a few millimetres (jumping spiders are about 4–12 mm) to several centimetres (wolf spiders about 13–50 mm). Web builders such as orb weavers sit in or beside silk webs; jumping spiders are compact, often hairy, and hop between leaves; wolf spiders run over the soil; crab spiders wait motionless on flowers and leaves. Spiderlings look like small adults.

Signs

No plant damage. Webs, egg sacs or small spiders on foliage and pots.

What favours it

Plantings with structure and shelter, such as perennials, grasses and mulch, and gardens where broad-spectrum pesticides are not used.

Prevention

  • Nothing to prevent in the garden.
  • Indoors, catch stray spiders and move them outside.

Treatment

Start with the first step and move down only if the problem persists.

  1. Leave them alone; killing spiders should be avoided where possible.
  2. Avoid broad-spectrum insecticides; choose cultural and mechanical pest controls so spiders survive.

Pros and cons

Pros

  • Generalist predators of many plant pests, including beetles, caterpillars, leafhoppers and aphids.
  • Hunt pests both indoors and outdoors.
  • Need no releases or purchases; avoiding broad-spectrum insecticides and leaving shelter such as grassy perennials or straw helps them.

Cons

  • A few species are dangerous to people (for example widow and brown recluse spiders in parts of North America); learn the local ones.
  • As generalists they also eat other spiders and beneficial arthropods.
  • Webs can be unwelcome indoors.

Look-alikes

Spider mites
Spider mites are tiny plant-feeding mites (under 1 mm) that make fine webbing on damaged, speckled leaves; true spiders are much larger and eat insects.

Sources

  1. Predatory Spiders — University of Maryland Extension
  2. Spiders — Colorado State University Agricultural Biology

Written in our own words from these sources. Check a product label before using any treatment.