Biological Control with Insects: The Waterlettuce Weevil

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Material Information

Title:
Biological Control with Insects: The Waterlettuce Weevil
Physical Description:
Fact sheet
Creator:
Center, Ted D.
Publisher:
University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication:
Gainesville, Fla.
Publication Date:

Notes

Acquisition:
Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
Publication Status:
Published
General Note:
"Revised: May 2002"
General Note:
"SS AGR 142"

Record Information

Source Institution:
University of Florida Institutional Repository
Holding Location:
University of Florida
Rights Management:
All rights reserved by the submitter.
System ID:
IR00004571:00001


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SS-AGR-142 Biological Control with Insects: The Waterlettuce Weevil 1 Ted D. Center, F. Allen Dray, and Vernon V. Vandiver, Jr.2 1. This document is SS AGR 142, one of a series of the Department of Agronomy, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Revised: May 2002. Please visit the EDIS Web site at http://edis.ifas.ufl.edu. 2. Ted D. Center, Research Entomologist, USDA Agricultural Research Service, Invasive Plant Research Laboratory, Fort Lauderdale, FL 33314; F. Allen Dray, Ecologist, USDA Agricultural Research Service, Invasive Plant Research Laboratory, Fort Lauderdale, FL 33314; and Vernon V. Vandiver, Associate Professor and Extension Aquatic Weeds Specialist, Fort Lauderdale Research and Education Center, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611. The Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension Service office. Florida Cooperative Extension Service/Institute of Food and Agricultural Sciences/University of Florida/Christine Taylor Waddill, Dean. ( Neohydronomus affinis Hustache Coleoptera: Curculionidae: Erirhinae: Stenopelmini) Host : Pistia stratiotes L. (Araceae) The genus Neohydronomus is comprised of three species whose native range is primarily South and Central America. All are semiaquatic, are covered with a layer of dense scales (not water-repellent), and feed on a single plant species, Pistia stratiotes in the family Araceae. Adult Neohydronomus affinis are small (3 mm long) and have a nearly straight rostrum that is strongly constricted ventrally at the base. N. affinis ranges in color from uniform bluish-grey to reddish-brown with a tan, chevron-like band across the elytra. The color pattern is associated with scales and may be difficult to distinguish if the scales are wet, dirty or missing. Females chew a hole about 0.5 mm in diameter in the leaf (usually on the upper surface near the leaf edge), deposit a single egg inside this puncture, and close the hole with a black substance. The larvae hatch within 4 days (at temperatures above 75F). The young larvae, which are very small, burrow under the leaf surface and work their way toward the spongy portions of the leaf at a rate of about 1.5 to 2.0 cm/day. The larval stage lasts 11 to 14 days. Under optimal temperatures, 4 to 6 weeks are required for N. affinis to complete the transition from egg to adult. Adults chew holes (about 1.4 mm in diameter) in the leaf surface and burrow in the spongy tissues of the leaf. The characteristic round feeding holes are easily observed when weevil populations are large (several hundred insects per square meter), but may be concentrated near leaf edges and more difficult to observe when populations are small. Self-perpetuating populations of N. affinis have established at several sites in southern Florida. The first experimental releases were made during 1987 at Torry Island and Kraemer Island at the south end of Lake Okeechobee. The weevils, in combination with native insects, subsequently caused dramatic declines in the waterlettuce populations at these two sites. The weevils have dispersed throughout the peninsular portion of the state and are impacting waterlettuce populations in other areas.