It's A Bug-Eat-Bug World: UF Researcher Imports Wasps From Caribbean To Control Destructive Root Weevils In Florida

December 27, 2001

HOMESTEAD, Fla. — When it comes to stopping one of the most destructive insect pests in Florida, it’s a bug-eat-bug world.

To control the Diaprepes root weevil on various crops, a University of Florida entomologist has imported three tiny wasps from the Caribbean and released them in five South Florida counties. Early tests indicate the wasps are providing effective control of the weevil without pesticides.

“Since its accidental introduction into Florida from the Caribbean more than 30 years ago, the Diaprepes root weevil has been impossible to eradicate and difficult to control,” said Jorge Pena, professor with UF’s Institute of Food and Agricultural Sciences.

The exotic weevil attacks citrus, ornamental plants, root crops, tropical fruit crops and grasses. Estimates show the weevil infests more than 100,000 acres of citrus and causes more than $70 million in damage annually.

“Despite all the damage, there is some good news,” said Pena, who has started a biological control program that uses wasps to attack the eggs of the Diaprepes root weevil. The wasps prevent weevils from reproducing.

“Biological control is appealing as a pest management tool because it relies on natural predators instead of pesticides. It’s nontoxic and often is self-sustaining,” Pena said.

Since the wasps already attack Diaprepes root weevil eggs in Puerto Rico, Guadeloupe and other Caribbean countries, Pena’s first goal was to import the wasps from the islands to see if they would become established in Florida. He brought three different wasp parasites into the state, placed them under quarantine conditions and then released them in test plots. The three parasites are identified by the following scientific names: Quadrastichus haitiensis, Ceratogramma etiennei and Aprostocetus vaquitarum.

Pena, based at UF’s Tropical Research and Education Center in Homestead, Fla., said female Diaprepes weevils lay their eggs in concealed sites, usually in the space between two adjacent leaves. Weevil egg masses are deposited in a gelatinous cement that seals the leaves together, protecting the eggs. Diaprepes eggs also are laid on broad-leafed plants, grasses and palm fronds. The parasitic wasps deposit their eggs into Diaprepes weevil eggs, preventing the Diaprepes weevils from emerging.

Working with the Florida Department of Agriculture and Consumer Services and various grower organizations, Pena has released more than 363,000 wasps of the species C. etiennei since 1998, more than 160,000 Q. haitiensis since 1999 and more than 50,000 A. vaquitarum since 1999.

He said the wasps were released in Florida citrus groves, ornamental plantings and undisturbed areas. C. etiennei wasp parasites have attacked Diaprepes eggs in Miami-Dade County. Q. haitiensis parasites have been found in weevil eggs in Miami-Dade, Glades, Hendry and Polk counties, and A. vaquitarum parasites have been recovered from weevil eggs in Indian River County. Pena said the findings indicate wasp parasites are becoming established in the state.

In fact, since their introduction, the wasps have begun to parasitize 35 percent to 100 percent of Diaprepes root weevil eggs in different crops.

“Although we’re finding more and more of the wasp parasites in citrus groves — which is good — we need some additional studies to measure their effectiveness. We also need to learn how pesticide application affects the survival of the imported wasp parasites,” Pena said. “We will continue releasing the wasp parasites in Florida and document how well they control Diaprepes root weevils.”