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Cliff Sadof, Entomologist and Peggy Sellers, Purdue University
Pine needle scale crawlers have been observed in Terra Haute; the needles were loaded with pine needle scale crawlers! Be on the look out for these and other armored scale crawlers such as euonymus scale and oystershell scale.
Scales thrive on trees and shrubs that are under stress. Maintaining plant health and conserving natural enemies are the best ways to prevent or minimize populations of scales. Reduce stress of trees and shrubs by planting in a suitable site and water and fertilize appropriately. Be on the lookout for small holes in the scales that show where parasitic wasps might have emerged. Also look for the larvae and adults of lady beetles that feed on scales.
Always look for signs of natural-enemy activity before deciding to treat with a pesticide. Summer oil treatment will smother actively crawling and recently settled crawlers. Look for crawlers by either examining twigs with a hand lens or by tapping a branch over a white sheet of paper. Crawlers vary in color depending on species. They are usually the size of a spider mite. Treat when you have a live scale population. Apply at the end of the crawler activity stage when scale covers are still clear. A 2% rate of ultra-fine horticultural oil is the best management option for homeowners. Although not labeled for homeowner use, professionals can use Distancẻ, an insect growth regulator with a high degree of success. When using any pesticide, read and follow label directions.
Refer to E-29W Scale Insects on Shade Trees and Shrubs (PDF 110K), for a complete list of scales and their hosts and several color photos.
Also, you can view a Euonymus Scale Crawlers Movie.
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Information listed is valid only for the state of Indiana.
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The Plant & Pest Diagnostic Laboratory at Purdue University.