It's time to talk about scales. Not the dusty one in your bathroom but the ones lurking in your landscape. Scale insects have no discernable head or legs, live under a waxy covering and suck plant juices. Despite their resemblance to helmets, their feeding can weaken and even kill trees and shrubs. The tricky part about scale is they often go unnoticed until they reach high populations. In addition several different scale species are possible.

Scale start out as eggs. The eggs hatch into crawlers that move along stems or leaves. Scale are not going to win any insect races. You can't expect much speed when the mobile stage of their life is called a crawler.

Once the crawlers locate a place to settle, they form a waxy coating then use their piercing mouthparts to suck out plant juices. Feeding causes leaf yellowing, plant stunting, and possible death of stems or entire plant.

Adult scale don't move for the most part and therefore look like part of the plant. To find out if your plant really has scale, take out your trusty horticultural tool, your thumbnail, and scratch the suspect bump on the plant stem or leaf. If it pops off then it may be scale. If it doesn't easily pop off, then it may be a lenticel or some other normal part of the plant.

A common scale is oystershell scale. It looks like, you guessed it, tiny grey or brown oystershells. Oystershell scale can be found on many plants including ash, redbud, birch, dogwood, elm, hemlock, lilac, maple, poplar, privet, walnut, and willow.

Euonymus scale is common on euonymus such as wintercreeper. Pine needle scale makes scotch and mugho pine look like white flocked Christmas trees.

As with many insect problems, stressed plants are more susceptible to attack than healthy plants. Therefore keeping plants healthy with proper watering and fertilizing will help. Prune out branches heavily infested with scale to quickly reduce populations.

Timing is very important with scale control using insecticides. Adult scale are difficult to control. They are most susceptible to insecticides in the young crawler stage.

Accurate identification of which scale is present is crucial. Once the scale is known then the timing for young crawler presence can be predicted.

One method of scouting for scale crawlers is to wrap a piece of black electrician's tape around a branch with the sticky side out during the time the crawlers are predicted to be present. Crawlers will get stuck on the tape as they try to crawl across it. Pine needle scale crawlers are dark red, euonymous scale crawlers are yellow, and oystershell crawlers are whitish. All of these colors can easily be seen on black tape.

The Vanhoutte spirea (Spiraea x vanhouttei) shrub can be a good indicator as to when to scout for oystershell, pine needle or euonymus scale crawlers. Drive down any older neighborhood now and you will see the arching branches of these large spireas covered in white flowers. Infested plants should be sprayed with an insecticide as Vanhoutte spirea is in full to late bloom. The gray-banded race of oystershell scale crawlers on ash, lilac, and maple are sprayed when Vanhoutte spirea has completed blooming. Spray oystershell brown race again in late June-early July.

There are several pesticides labeled for scale control such as acephate (Orthene), insecticidal soap, and horticultural summer oil. Generally multiple sprays ten to twelve days apart are needed.

Dormant season oil sprays are not effective for oystershell scale control. Scale control requires vigilance. Be sure to read and follow all pesticide label directions.