I first wrote about crape myrtle bark scale three years ago in a column in fall 2017. The pest, discovered in Texas in 2004, popped up in Chesapeake six years ago, and later in Virginia Beach. Options for control for the new area pest included exclusion, plant selection, plant destruction, and chemical and biological controls. The pesticide treatments that looked most promising were soil-applied systemics that were costly and might be difficult for the homeowner to apply. Peter Schultz, emeritus professor of entomology at Hampton Roads Agricultural Research and Extension Centers wrote me to share that his research was yielding some encouraging signs of biological control — predation of bark scale by ladybugs.
A recent question from a Hampton reader regarding crape myrtle prompted me to revisit this topic and to catch up with Schultz for an update. While now “retired,” Schultz continues to study and monitor the movement of the pest in Hampton Roads. A couple of weeks ago he wrote:
“The CMBS is a fascinating story first seen in Chesapeake in 2014, and quickly had more reports mostly Chesapeake and Virginia Beach. Backing up, with your help from readers, I identified 163 locations in 2017, and then a dramatic decline to 44 in 2018, 10 in 2019, and 5 so far in 2020. The new reports are coming in from farther west, Hampton and Smithfield (first in 2018), Yorktown (this afternoon). I suspect some under reporting this year might be from our preoccupation with health and safety.”
Schultz continued: “Yesterday, I visited a new site in Virginia Beach (Thoroughgood), and found more ladybug larvae (Hyperaspis bigeminata) than live scale. This leads me to speculate that the population crash (decline) is due to the voracious appetite of these beetles who went wild with the high amount of food source from the scale explosions of a few years ago. Another factor — there are systemic insecticides applied as a drench or bark spray sold in garden centers that are very effective in killing the scale (and of course the predator ladybugs. Both methods worked to eliminate the scale. Obviously, the soil application is faster; however, those interested in control without insecticides have an ally in this small ladybug whose larvae are easy to differentiate from the scale (a previous article of yours went over this).”
Keep your sightings coming to Schultz and keep befriending those ladybugs. He can be reached at schultzp@vt.edu.
And one more thing
Last weekend was a milestone of sorts for me. I began my post-retirement, part-time job as The Virginian-Pilot’s “Gardening Q&A” columnist on Sept. 17, 2016. Last week’s column was my 210th consecutive. It has been a challenge to strike a balance between technical and practical — appeal to the layman, as well as those with some horticulture background. I sometimes wander into the weeds — it’s the old horticulture professor in me.
Not, by any means, does all of the correspondence I receive make it into print. Nevertheless, I do try to respond to everyone, and in as timely fashion as possible. If I’ve missed a response, it was certainly not my intent — some weeks my inbox gets full. Don’t be afraid to send me a reminder.
I truly appreciate The Pilot’s giving me this opportunity and the many readers who have written in with questions and gardening experiences (whether good or bad). I’m still enjoying the ride — thank you.
Send questions to wkspen@gmail.com.
