We turn our attention this month to the Dallas-Fort Worth Metroplex, which has been beset by bugs of vastly different origins and effects. One attacks – rather, it attaches itself to – crape myrtle. The other hatches in water, lurks in foliage and emerges primarily at dawn and dusk to attack humans. Relentlessly.

Scale has infested crape myrtles in the Dallas Fort Worth Metroplex, and ongoing research will determine whether it’s a new introduction of an Asian pest.
Photo by David Morgan

Eriococcus lagerostroemia?

First, it appears that crape myrtles throughout the region are bespeckled with a scale of unconfirmed lineage. So far the damage has primarily been aesthetic; although the plants are stressed, there have been few reports of tree death as a result of the infestation.

The scale’s not exactly new, having been spotted first in Richardson, Texas, in 2004, when it was tentatively identified as azalea bark scale (Eriococcus azaleae). But azalea bark scale wasn’t known to affect crape myrtle, and so in 2010 samples were sent to Dr. Dug Miller (yes, his name is spelled Dug; it’s short for Douglass), a research entomologist in the Systematic Entomology Laboratory at USDA’s Agricultural Research Service facility in Beltsville, Md. This is the man you want on the case: he’s a coccidologist with nearly 30 years of experience.

Miller determined that the scale affecting crape myrtle in northern Texas could be a new introduction of Eriococcus lagerostroemia, crape myrtle bark scale, previously known only in Asia. The jury’s still out, though, because even Miller was unable to detect obvious physical differences between the two scales, and so the next step is a DNA analysis.

In the meantime, Dr. Michael Merchant, professor and extension urban entomologist for TAMU’s Texas AgriLife Extension Service, is working to help crape myrtle owners and growers battle the bug. His lab received a grant in 2008 to study the effectiveness of various insecticide treatments, and his research concluded that significant control could be realized with drench applications of acetamiprid, clothianidan, dinotefuran and/or imidacloprid, all of which are available commercially. Longevity of control remains to be determined.

Other control options include washing the trunk and other limbs with a soft brush and a mild solution of dishwashing soap, which removes many of the female scales and egg masses. This also helps to increase the effectiveness of insecticidal control. Such scrubbing (gently, please) will remove that nasty black mold that appears on infested bark. Beneficial predators, such as lady beetles, may also work.

Horticultural oil hasn’t proved effective, but Merchant says that a winter application of dormant oil may help. A higher application rate during winter can be used without damaging the plant – thorough coverage is recommended.

This scale has not yet been confirmed outside the north Texas region, and it’s hoped that adequate management can prevent it from spreading.

West Nile virus, spread by infected mosquitoes, is at record levels this season, according to the Centers for Disease Control. The Dallas Fort Worth Metroplex has been particularly hard hit, with Texas logging nearly half the number of cases reported in the U.S.
Photo courtesy of Jim Occi, BugPics; Bugwood.org

Mosquitoes and West Nile virus

This summer is on pace for logging a record outbreak of West Nile virus – according to the Centers for Disease Control, we stand at three times the number of cases reported for this time of year, with one expert stating it’s “one of the largest outbreaks” since the virus was first reported in the U.S. in 1999. As of late August, 1,118 illnesses had been reported (in an average year, fewer than 300 cases occur); 41 deaths have been recorded.

Forty-seven states have reported West Nile virus infections in people, birds or mosquitoes; approximately 75 percent of the cases are in five states – Texas, Mississippi, Louisiana, South Dakota and Oklahoma. In Texas, the state reports that 586 cases have been reported; of those, 340 are in Dallas and Tarrant Counties. However, local health department officials counted 474 cases in those counties as of August 21.

We keep using the word “reported” because West Nile is difficult to track. Many who experience symptoms recover quickly without intervention; some who may be infected never experience symptoms at all. Those who are affected by a full-blown case, however, may be left with life-altering nerve damage. Or worse.

Landscapers, growers, you know the drill. You’re out at dawn and don’t finish the job till after dusk. Dawn and dusk are prime time for bites, so protect yourself. Cover up, apply DEET, avoid standing water. It’s easy to get bit; it’s easy not to know you’ve been bit. But if you begin to experience flu-like symptoms, get tested right away. Better safe than sorry.