Question
QUESTION: Dear Jack - I am trying to figure out what is on the underside of many of my shrubs' leaves this spring.  I live in the foothills of NC and have noticed an unusual white thing under many of the leaves near the upper part of my foundation shrubs (I do not know what shrubs they are - they were here when we moved in!)  The white substance almost looks like a worm's body, but it does not look alive and it also looks like a tunnel or a cocoon that an insect has come out of.  But these tunnels are very small(1/4 inch) and flattish and there are sometimes 10 of them on one leaf.  I am having trouble even knowing how to search for the identity of such a thing!  Any ideas?  Thank you!

ANSWER: Cari,

You may be describing a cottony scale. Take a look at this page http://www.livingwithbugs.com/sca_ins.html for a picture and google "cottony scale" for more pictures. If this seems right post a follow up and we can discuss what to do next.

Jack DeAngelis
http://www.livingwithbugs.com



---------- FOLLOW-UP ----------

QUESTION: Yes, thank you!  That is exactly it!  The very first picture was spot on.  What is your recommendation?

Answer
The cottony sac is made by a scale insect that lives beneath the cotton. Scale insects are related to aphids and feed on the sap of the plant. Scales make honeydew so the leaves may be covered with black sooty mold that is growing on the honeydew.

Scale insects can be difficult to control at this stage. Sometimes systemic insecticides like imidacloprid (Merit or Bayer Advanced) are effective (see http://www.livingwithbugs.com/merit_insecticide.html for a Merit label) but be sure that your particular plant is listed on the package label. You can also just physically remove the scales by washing the leaves with insecticidal soap if the plant is not too big. In any case scale insects are probably a long-term project that will require some type of treatment most years, especially on susceptible plants.

Good luck.

Jack DeAngelis
http://www.livingwithbugs.com