Entomology and Plant Pathology, Oklahoma State University
127 Noble Research Center, Stillwater, OK74078
Vol. 11, No. 29
May 24, 2012
Kermes Scale Causing Problems for Oklahoma Oaks
Eric J. Rebek, Extension Entomologist Horticultural Insects
The Plant Disease and Insect Diagnostic Lab has received several reports of oak leaf/twig drop across Oklahoma in the past few weeks. From post oak samples we’ve collected in Logan County, the culprit appears to be a kermes scale called pubescent leaf kermes, Nanokermes pubescens. Populations of these scales are swelling on white oaks, especially post oak. We suspect this population explosion is the result of a very dry growing season in 2011 followed by somewhat wetter conditions this year. This report describes how to identify pubescent leaf kermes, its
life cycle, preferred hosts, associated damage, and management. Keep in mind that infestations of kermes scales are not likely to cause tree mortality, but excessive leaf drop will cause some concern among homeowners and landscape professionals.
Adult females measure approximately 1/8 to 1/4 inch in diameter. They are globular, immobile, hard-shelled, and reddish-brown to nearly black with brown specks. In general, they appear gall like and are found clustered around the leaf base and petiole. Many times these can be mistaken for buds or developing acorns. Adult males are gnat-like, have only
two wings, and are short lived so they are not commonly seen.