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Florida Lake Management Society Annual Conference, Naples, Florida, June 4 – 7, 2007

USE OF BIOCONTROL INSECTS TO CONTROL INVASIVE AQUATIC PLANTS

Charles E. Ashton U.S. Army Corps of Engineers Jacksonville, FL

Alligatorweed (Alternanthera philoxeroides) was introduced into the United States from South America in the late 1800’s and became problematic in the southeastern United States. This sprawling emergent plant formed dense floating mats which once grew across many narrow rivers and canals. In 1959, cooperative efforts on biological control of aquatic plants were initiated between the U. S. Army Corps of Engineers and the Agricultural Research Service, U. S. Department of Agriculture. Overseas searches began for potential biological control insects to

control alligatorweed in the 1960’s.

These searches produced three insects, which have proven

to

be

very

successful

in

controlling

alligatorweed

in

much

of

the

southeastern

U.S.

All

biological control insects go through can be released. The alligatorweed (Amynothrips andersonii), and the

an extensive screening and quarantine process before they flea beetle (Agasicles hygrophila), the alligatorweed thrip alligatorweed stem borer ((Vogtia) Arcola malloi) were

released in established

Florida in 1964, 1967 and 1971 respectively. These insects have been successfully in most of the southeastern United States and successfully control alligatorweed.

Three

years

after

the

introduction

of

the

alligatorweed

flea

beetle

in

Florida,

the

U.S.

Army

Corps of Engineers Jacksonville District stopped herbicide spraying for alligatorweed The insects have not eliminated alligatorweed but they have keep populations at a low

in Florida. level.

In 1980, a freeze in northern Florida depleted the alligatorweed flea beetle population to such an extent that alligatorweed populations began to be a problem again on the St. Johns River. Staff was sent to South Florida to collect and repopulate the St. Johns River with alligatorweed flea beetles. In a short time, the insects brought the problem weed back under control. Due to this successful effort, it was determined that it may be possible to expand alligatorweed biological control efforts into colder climates by introducing alligatorweed flea beetles in the spring. In 1981 a program was established to provide alligatorweed biocontrol insects to states where the insects did not over-winter. The collection and distribution of the alligatorweed flea beetles was the primary focus of the effort.

The adult alligatorweed flea beetles are black with yellow stripes. The adults have well developed flight muscles and travel to new areas in search of food. All life cycles feed on alligatorweed. A female can lay approximately 1000 eggs in her lifetime. The entire life cycle including adult, egg, larvae, pupae, and adult is completed within 30 days. In 1964, the beetles were released on the Ortega River in Jacksonville, Florida, and by 1965 the alligatorweed had been controlled. Unfortunately alligatorweed will grow further north than the biocontrol agents. The beetles will not survive freezing weather, so beetles do not over-winter in these climates.

Headquarters, U.S. Army Corps of Engineers, established the APCOSC located in the Corps of Engineers Jacksonville District to serve as the Corps-wide center of expertise in the operational aspects of aquatic plant management. As part of these services, the center provides alligatorweed biocontrol insects to public agencies that have alligatorweed problems. The U.S.

Session 6A – Page 2

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