Predator thwarts cycad scale

King and queen sagos are extremely susceptible to attack by Asian cycad scale. At its worst, an infestation can completely coat a medium-sized sago within months and kill it within a year. But Researchers at the University of Florida’s Tropical Research and Education Center in Homestead have introduced two natural enemies to help combat this pest. But these predators are not completely effective.

The natural enemies are a predaceous beetle and a parasitic wasp. The adult beetle feeds primarily on adult female scale. The beetle lays her eggs among the scale eggs underneath the scale armor covering. After hatching, the beetle larva feeds on all stages of the scale. The wasp attacks and kills female scale by laying its egg inside the female scale where the developing wasp larva feeds and grows.

“Both of these natural enemies have become established in many areas of South Florida and contribute to the control of the scale,” said Catharine Mannion, assistant professor of ornamental entomology at UF’s Institute of Food and Agricultural Sciences.

“However, because of the explosive nature of the scale insect, neither one of these natural enemies can provide complete control.”

The Asian cycad scale was accidentally introduced to the Miami area from Southeast Asia, she said.

“Within a few years, 80 percent of the king and queen sago palms in South Florida were killed, and the pest has killed almost half of the king and queen sago palms in Central Florida. The cycad nursery industry has been devastated, with economic losses in the millions,” she said.

Horticultural oils and/or insecticides can be used to manage Asian cycad scale, she said. Thorough coverage of the plant is extremely important when applying a spray and repeat applications may be necessary, she said.

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For more: Catharine Mannion, University of Florida, (305) 246-7001, Ext. 220; cmannion@ufl.edu.