Molecular Diagnostic for I.D. of Crape Myrtle Bark Scale Insect
The Problem
Crape myrtle bark scale is an insect pest of crape myrtle, one of the most popular flowering shrubs in the U.S. Since first detected in Texas in 2004, this pest has spread to 12 states, including Arkansas, causing economic losses and aesthetic injury. An effective genetic tool was needed that could identify crape myrtle bark scale eggs and adults.
The Research
Allen Szalanski, a Division of Agriculture entomologist, led a team of researchers to develop a molecular diagnostic technique to identify crape myrtle bark scale from other scale insects using a PCR primer specific for this pest in a multiplex PCR reaction using a region of the mitochondrial DNA cytochrome oxidase I gene.
Egg and adult samples were obtained from Arkansas, Texas, and Virginia. Samples were first subjected to DNA sequencing of a region of the mitochondrial DNA COI gene and verified with sequences deposited in GenBank. Based on the DNA sequence data, a new PCR primer specific for crape myrtle bark scale was developed.
The multiplex PCR molecular diagnostic technique was performed on four unknown scale insect samples collected from Texas, as well as an unknown egg sample from Virginia. The diagnostic test confirmed that all unknown samples were crape myrtle bark scale.
Szalanski in collaboration with Dr. Peter Schultz, Virginia Tech University, was able to identify crape myrtle bark scale on St. Johns Wort and American beautyberry, the first record of these hosts for this insect in the United States.
The Bottom Line
The development of a molecular diagnostic technique using PCR to identify crape myrtle bark scale eggs and adults from other scale insects will enhance monitoring of this invasive species in Arkansas and other states. It is especially useful when only eggs are found since the pests cannot be identified by morphology at this stage. The developed genetic tool also verified a previously unidentified host plant for the pest, helping to close a previously unknown avenue for the spread of the invasive species.
The Researcher
Allen L. Szalanski
Professor; Department of Entomology and Plant Pathology since 2006.
Szalanski earned his bachelor’s degree in entomology from the University of Manitoba, his master’s degree in entomology from Kansas State University, and his Ph.D. in entomology from the University of Nebraska-Lincoln. Research interests include molecular diagnostics of economically important invasive insects and genetic variation of termites and honey bees.
»