John Cannon, Manager of Stiles Landscape Company’s lawn and ornamental pest control division, stopped a potentially devastating pest to trees and shrubs in several areas of Broward County, FL. But lobate lac scale, a native of South Asia, isn’t likely to go away, especially in Florida.

It took a sharp eye to detect the tiny lobate lac scale (top). The difference between the treated and untreated trees (below) is dramatic.

Cannon, an ISA Certified Arborist as well as a Certified Pest Control Operator, first noticed the “unbelievable devastation” of the scale in January 2002 in Palm Beach, FL. Overnight, the pest coated the stems and small branches of several of his wax myrtles, silver and green buttonwoods, coco plums and ficus trees.

The problem: How to control it?

Cannon sent a sample to the Florida Department of Agriculture and Consumer

Services. Two weeks later, lobate lac scale was confirmed.

“This scale was different than anything I had seen before, not only in terms of the sheer number covering the plants but that it was feeding on stems, not leaves,” says Cannon, a 16-year industry veteran. “I was hesitant to invest in a treatment that I wasn’t sure would work.”

Cannon reached out to Dr. Avas Hamon, an entomologist with the Florida Department of Agriculture and Consumer Services, Division of Plant Industry, and Jorge Moreno, a field sales representative with Bayer Environmental Science. They decided to try using imidacloprid (Bayer’s Merit WP 75 insecticide).

The team started with a test on eight medium-sized (12-ft. high) wax myrtles. They sprayed a Merit solution at labeled rates directly on the leaves, and allowed runoff to soak the roots. Three weeks later, the black sooty mold seemed less prominent.

The solution: soil drenching, root injections

Cannon and Moreno moved on to six 40-ft. ficus trees, now almost encased in black soot, with only 50% remaining leaf cover.

The height of the trees meant they wouldn’t be able to spray. They decided to test both soil drenching and deep root injections (6-in. deep in a grid pattern). On April 11, 2002, they deep root injected three trees, soil drenched three others and left one per treatment as the control. The labeled amounts applied to each tree were based on the diameter of the trees at breast height (DBH).

The application was made two feet away from the trunk and extended out to the dripline. A pound of 20-20-20 fertilizer per tree was also added to the mix to help with solution uptake.

Cannon and Moreno checked back on the trees every 30 days. On their first return visit, they saw a reduction in scale.

Without reapplying, Cannon reports that all six of the treated trees are “clean as a whistle” 12 months later. The untreated control tree continues to be plagued with sooty mold. All treated trees have regained their lush growth. He continues to use imidacloprid on other accounts when any sign of the scale is present.

For more information on the trials explained in this story, contact John Cannon at 954/781-0247 or Brian MacCurrach, Bayer Environmental Science, at 863/678-3100. lm