We can’t see most of the soil-dwelling creatures in our garden, but we can see some without magnification. Most of us know what earthworms look like, and that they’re beneficial (apparently video game addicts do not) and harmless to humans.
Earthworms churn the soil, enabling the incorporation of oxygen and water penetration, their excrement enriching the soil. They eat decaying roots, leaves and some living organisms such as bacteria, nematodes and fungi. Their feeding further shreds and breaks down organic material so smaller creatures can consume it. There’s plenty there for all, since one teaspoon of healthy soil contains a million to a billion bacteria plus fungi, protozoa, nematodes and arthropods (creatures with jointed legs, many of which are visible without magnification).
We’re usually not sure of the helpfulness of arthropods (creatures with jointed legs) in our soil. There are sowbugs and the closely related armadillidiidae, or pillbugs, that youngsters touch to get them to roll into a ball. These are not insects, but isopods, having evolved from sea- to land-dwelling creatures. They’re also known as roly-polies, slaters, wood lice or, in the Pacific Northwest, “potato bugs.” Since they lack the hard carapace (shell) of insects that retains moisture, they inhabit moist dark spaces to retain body liquids and are active mainly at night. They appear as segmented creatures, two legs per segment.
Their avoidance of bright light enables students to study their learning ability in mazes, substituting these widely available creatures for more expensive lab animals such as rats or mice. Sowbugs are often accused of plant destruction, but their actual damage is fairly rare. Another creature has started the plant injury and moved on, and then the sowbug moved in to feed on the now-decaying plant, and it becomes the “deer in the headlights,” the one surprised in the act.
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There are poison sprays available that kill sowbugs, but unless you have strawberries hanging to the ground that sowbugs will eat, their damage is so slight it’s not worth the cost in terms of money and soil damage. All pesticides can kill microscopic soil-dwelling creatures as well as those destructive insects you’re targeting.
We also have numerous millipedes in our soil. Some look like earthworms, but move differently, alerting you to look for their many legs. They have two pairs of legs per body segment. They also have a glossy “shell,” whereas earthworms are soft and moist. Millipedes mainly eat dead plant matter, but will chew on live roots if there’s insufficient plant matter for them. Fruit fallen to the ground is quickly occupied by millipedes. Their idea of “dead” differs from ours.
Another visible creature is the symphylan, and it looks like a whiter and smaller version of a centipede. In large numbers it can be a destructive plant pest, since it feeds on plant roots. Click beetles, those whose bodies are straight and slender, are parents of wireworms, those segmented yellow legless worms that damage potatoes, onions, carrots and beets. The adults spend most of their time above soil, and so do earwigs, after they’ve matured, leaving their offspring underground.
what’s up, hellebores?
Have you taken a good look at your hellebores lately? A devastating disease has appeared in this area, called helleborus black death. Its cause has not been discovered, but experts suspect it’s a virus. It’s appeared in the Pacific Northwest, some Eastern states and some other countries. Some references report it has not been observed on H. niger (blooms white or soft pink) or H. argutifolius (aka H. Corsican) that blooms green. It mainly appears on H. orientalis, now known as H.x hybridus, that blooms white, and pink to purple, with spots and yellow stamens.
Symptoms are black veins on leaves, brown or black streaks on petioles, black streaks on flower bracts and stunted, brittle new growth. It mainly appears on new foliage of older established plants. Infected plants do not recover, so should be dug and removed. Do not add to compost pile.
Send garden questions to firstname.lastname@example.org or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.