The cobweb spider is the homeless vagrant of the spider world. Rather than build and repair a strong, long-term dwelling in a good location as does the classic orb weaver, it builds and camps in a small, quick, weak web anywhere it can find a surface to sling it, preferably out of the rain, but anywhere in dry weather, like now.
As soon as its web gets dirty, visible, and therefore useless, it moves on and builds another nearby. The dirty webs actually steer its prey into the invisible new web. And they can make even a pretty shrub or house look neglected in short order.
I saw this effect on one of my most beautiful properties, when a mister showed up the cobwebs that had appeared on the ground cover overnight. Approaching the door, I saw a piece of litter, a gas receipt, crumpled and thrown on the ground cover by someone who had actually been at her door. Unconsciously, the person saw the cobwebs and threw his trash into the ugliness of the webs, despite the beauty of the rest of the property. A few webs are all it takes to turn on the unconscious urge to litter.
Cobwebs are all over town, particularly infesting hedges and certain shrubs that they favor, like juniper and rosemary, but also every neglected inward corner of a building, particularly under the eaves.
I’ve been petitioning door-to-door lately, and the cobwebs around the front doors make one shudder. Your gardener or landscape maintenance man cannot visit often enough to clean these up; it is up to residents.
The way to actually discourage these spiders is to sweep their webs before you see them, while they are still useful to the spider. If you only sweep the visible webs, you aren’t even bothering the spiders.
Sweep every corner where they might build, particularly where you see a spider but no web. When you sweep them off a building, it pays to stick around for a minute or two while they start climbing right back up where they were, and sweep them down again. This will often make them go somewhere else.
Another way to clean up cobwebs is with a hard jet of water; this is probably more effective than a web duster in shrubs, which are invaded only in dry weather, and where it is impossible to sweep all the webs.