Villains of the Spring Garden

You don’t need a calendar to tell you that spring has arrived, and along with it – bugs.  A portion of a tree, suddenly stripped of its leaves that’s now home to a wiggling clump of fuzzy caterpillars. A pulsating mass of tiny pests cloak the new growth on your roses, elderberries or peach trees, or seedlings just beginning to develop, disappear overnight.  Who are these marauders and how does one deal with them? 

A few of the major villains in the spring garden are aphids, caterpillars (particularly tent caterpillars), snails and slugs, and scales. Some are easy to recognize and manage while others require more monitoring and rigorous control measures.

One of the most prevalent and recognizable spring pests is the aphid. These small, pear-shaped, often green soft-bodied insects suck the juices out of a wide variety of plants. Frequently seen in masses covering new growth on plants, they can weaken a plant, cause leaves to yellow, curl or drop early or distort plant stems or fruit.  As they feed, they produce honeydew that attracts ants that in turn, protect the aphids from various predators. Any honeydew the ants don’t consume can end up supporting the growth of black sooty mold.

The best method of control is prevention. Aphids love rapidly growing supple new growth on plants that get a lot of nitrogen fertilizer, so switch to a slow-release organic material. Aphids are the favored food of many natural enemies including lady beetles, soldier beetles, and lacewings, so encouraging beneficials into your garden can often keep aphid populations in check. A blast of water is usually enough to knock them off the plant. 

The tent caterpillar, a rather furry-looking reddish brown, with blue spots and tufts of orange to white hairs, is also easy to recognize. Generally seen in huge numbers within their silken webs, they feed on deciduous trees and shrubs including ash, birch, fruit and nut trees, madrone, oak, poplar, redbud, toyon, and willow. Their damage can be slight to serious on individual trees depending on the level of infestation. Inspect plants regularly, and if you see these voracious pests, prune out the infested branches and dispose of them.

You may not see snails and slugs, but you can sure see their damage.  These slimy mollusks emerge from hiding at night and chew holes in leaves and flowers of many garden plants and fruit. Slugs (the ones without an external shell) and snails move by gliding along on their muscular “foot” that constantly secretes mucus forming their trademark silvery trail.

Check out your plants very early in the morning, and you’ll likely find them moving back to their daytime hiding places – ivy, weedy areas, debris, boards or other dark, moist, protected locations. An integrated management approach that includes reducing moisture and hiding places, trapping, barriers, and handpicking is the most effective.

Scale looks like bumpy, crusty bark or fine ash on branches of trees and shrubs. They are another insect that sucks sap from the plant, weakening it and causing dieback of twigs and stems.  They produce that sticky honeydew the ants love, that supports black sooty mold.  Your best bet is to prevent infection through good garden sanitation, monitoring susceptible plants and treating any visible signs immediately.  Prune away and destroy infected canes. 

For more information on any of these springtime pests or garden problems, contact the Master Gardener Help Desk at

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