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Mr. Smarty Plants - Insects along branches of cedar elm

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Thursday - April 14, 2011

From: Austin, TX
Region: Southwest
Topic: Trees
Title: Insects along branches of cedar elm
Answered by: Nan Hampton and Eric Beckers

QUESTION:

I have a 10 foot Cedar Elm planted three years ago. The smaller branches have what looks like incubating red pellet-like insects in a soft, putty colored glob--one insect per glob. They are all along the branches. It looks as if those branches will not leaf out although uninfested ones are doing so. Are these insects causing permanent damage and can/should I do anything to get rid of them? Thank you.

ANSWER:

I contacted Eric Beckers with the Texas Forest Service who agrees that your description sounds like lecanium scale insects.  University of California Integrated Pest Management (IPM) has a list of many scale insects (with links to photos of most) and their hosts.  Horticultural oil is a good treatment but it should have been applied in their overwintering stage to be most effective.   You can still do a summer weight oil application but you need to be very careful to avoid the new foliage when applying it.  Other possibilities for treatment are listed in the two links (above) about scales.  Eric reminds you that it is very important to maintain adequate moisture on those easily stressed new trees. 

 

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