Efficacy of a horticultural oil + insect growth regulator mix (SuffOil-X + Molt-X) and two imidacloprid formulations (Bayer Tree and Shrub; Fertilome Tree & Shrub Systemic Insect Drench) were tested for control of bark scale (Eriococcus lagerostroemia) on crapemyrtles at LeTourneau University. There was a trend towards decreasing alive scales and decreasing alive:dead scale ratio with time, especially by the fifth week in all treatments (including the control). The systemic insecticides (imidacloprid) demonstrated a decrease in alive:dead scale ratio two weeks after treatment, whereas contact treatments showed a decrease one week after treatment (horticultural oil + insect growth regulator). Since the control also showed decrease in scale populations, in some cases before other treatments, the efficacy of the insecticides studied here are inconclusive.
On June 24th and 25th (2014), a number of Texas A&M AgriLife personnel set out to McKinney to collect data on susceptibility of different varieties of crape myrtles to the new invasive pest, crape myrtle bark scale (CMBS). McKinney is home to over 114 varieties of crape myrtles from all over the world, making it a great site to investigate the preference of CMBS for certain cultivars and varieties. Follow the gallery below to see how the research was carried out.
McKinney – home to the crape myrtle world collection park. Naturally a great place to look for crape myrtle bark scale infestations.
McKinney crape myrtle bark scale infestation assessment team (2014). From left to right, Dr. Mike Merchant, Neil Sperry, (front) Dr. Mengmeng Gu, (back) Erfan Vafaie, Laura Miller, Janet Laminack.
McKinney crape myrtle bark scale infestation assessment team (2014). From left to right, Dr. Mike Merchant, Susan Owens, (front) Dr. Mengmeng Gu, (back) Erfan Vafaie, Laura Miller, Janet Laminack.
Dr. Gu, Extension Horticulturalist from College Station, can barely stand the site of infested crape myrtles.
First step, assess overall infestation.
Using a scale from 1 (low) to 9 (high), researchers determined the level of scale infestation by visual observation.
In addition to level of infestation, level of sooty mold coverage is also assessed.
Water sensitive cards can be used to estimate the level of infestation. The excreted honeydew from the scales hits the card and turns it blue. This is an example of a highly infested tree.
Ms. Laminack measures the circumference of the trunks.
Dr. Gu recording the data.
A few branches were cut from each tree to assess infestation levels under a microscope.
Every branch has to go into a labelled bag!
Crape myrtle bark scale on the main trunk
Sooty mold on some cultivars gave them an appealing pattern.
High level of crape myrtle bark scale on upper branches. Two lady beetle larva are amidst the scales, presumably having a casual afternoon buffet.
Very high level of crape myrtle bark scale infestation.
Although many trees were infested, the blooms were still gorgeous.
The excreted honeydew can serve as a meal for wasps.
Classic thrips damage at the tips of the flowers.
Acrobat ant (Crematogaster spp.) swarm! The ‘swarmers’ are winged.
Queen acrobat ant takes a break. It’s been a long day for her.
Praying mantis eggs case? If it is, great! Praying mantids are predators of many unwanted pests.
Adult lacewing, a predatory insect that eats a lot of pests.
Wheel bug, a type of assassin bug (predatory) that apparently has a nasty bite. It’s pretty, but no touchy!
Crape myrtle trails span across the road medians in McKinney.
Looks a lot like the twice-stabbed lady beetle, Chilocorus stigma, a beneficial predatory insect!
We found a lot of these beneficials. They look like mealybugs, but they are actually a type of ladybeetle larva (possibly Scymnus or Hyperaspis lateralis) that feeds on scales. Some of the other species we saw included Chilocorus cacti and C. stigma.
A new invasive scale of crape myrtles has recently been detected. Current evidences suggest that the species is Eriococcus lagerostroemia, a native to the plant host to Lagerostroemia sp., also found in China, Japan, Korea, India, Mongolia, South Korea and United Kingdom.
Black sooty mold coloring the originally red-colored bark.
CMBS nymphs, sometimes referred to as crawlers, tend to be found in clusters.
Black sooty mold often covers the top part of the bark infested with CMBS