It is obvious now that our widespread mysterious symptoms on crape myrtle trees were
due to herbicide injury, rather than an infectious causal agent, such as phytoplasmas.
Symptoms of both can be very similar. The far ranging occurrence of the symptoms
and time of year it happened, made it hard to believe that herbicides were the cause.
I had received assurances that no herbicides were used broadly like that in our city.
However, I had not then found the right City department to interview.
After many weeks of interviews with homeowners, and city workers, after getting the
results of the plant clinic at NC State University and USDA Laboratories in Washington, DC,
I have concluded the entire problem was due to widespread herbicide injury by city workers'
application of glyphosate to the curbs in certain neighborhoods on hot, perhaps breezy days,
in April 2012. We had some days in that month when the day time high temperature reached 89 F.
This was very unusual weather. Other neighborhoods which received identical treatments showed
little or no reaction from the crape myrtle trees in their vicinity.
I have educated staff of the City of Elizabeth City on drift reduction nozzles and drift reduction
adjuvants, useful for the spraying of herbicides, to keep them on-target. We also discussed the
relative volatility of various herbicide formulations. We've also discussed pre-emergence chemicals
which may substitute for, or augment glyphosate use, requiring less glyphosate to be needed.
I'm glad the crape myrtle trees will be fine." -- Margaret Pooler, research leader, USDA/ARS U.S. National Arboretum, Floral and Nursery Plants Research Unit
Meet the plant
Learn about the 29 U.S. National Arboretum crape myrtle introductions at: http://www.usna.usda.gov/PhotoGallery/CrapemyrtleGallery/index.html