University of Maryland Extension

Monitoring Scale Insects: Focusing on the crawler stage

Since 2010, we have been monitoring Japanese maple scale populations to determine the life cycle of this scale insect in Maryland. In 2013, we added Indian wax scale, white prunicola scale and juniper scale to the monitoring list to better determine crawler periods. There are systemic insecticides available that can be used to control scale. And, when the scale goes to crawler stage, contact insecticides such as insecticidal oil and Distance can be used. These spray applications are most effective when timed at the height of crawler activity. We are correlating insect activity with growing degree days (base temperature of 50 °F) and plant phenological indicators if available.

* The charts show the number and timing of the scale crawler generations. A summary of the 2013 monitoring program will be posted when available.

Japanese Maple Scale (JMS)

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Japanese maple scale on stemThere are two overlapping generations of Japanese maple scale crawlers.  JMS overwinter as immature 2nd instar males and females. For more information.
Japanese maple scale

Indian Wax Scale

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Indian wax scale on stem
Overwintering female Indian
wax scale
Indian wax scale flipped over to show eggs
Eggs under the female cover
Indian wax scale crawlers
Crawlers and settled stages

2013 Monitoring at Columbia, MD Site:
June 17 at 854 DD - First crawlers
June 24 at 985 DD - Many crawlers and a few settled stages
July 2 at 1173 DD - A few crawlers, mostly settled early stages
July 8 at 1570 DD - All settled stages
There is one generation per year.

White Prunicola Scale

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White prunicola scale covering stem

This scale is commonly found on Prunus species and is also seen on magnolia, ligustrum, rhododendron, forsythia, boxwood, and lilac.

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