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ARS Home » Southeast Area » Fort Lauderdale, Florida » Invasive Plant Research Laboratory » Research » Publications at this Location » Publication #247641

Title: A Simple, Efficient Method for Extracting Neochetina eichhorniae and N. bruchi (Coleoptera: Curculionidae) from Waterhyacinth (Eichhornia crassipes: Pontederiaceae)

Author
item Center, Ted
item Dray, F Allen

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2010
Publication Date: 6/10/2010
Citation: Center, T.D., Dray Jr, F.A. 2010. A Simple, Efficient Method for Extracting Neochetina eichhorniae and N. bruchi (Coleoptera: Curculionidae) from Waterhyacinth (Eichhornia crassipes: Pontederiaceae). Florida Entomologist. 93(2): 315-316.

Interpretive Summary: The weevils Neochetina eichhorniae Warner and N. bruchi Hustache were released in Florida to control the floating weed waterhyacinth but results were variable, with excellent control occurring in some cases but not in others. We have have found that poor host quality seems the most likely explanation for low weevil populations and the failure to achieve adequate control in some areas. One approach to overcoming this difficulty might therefore be to mass rear large numbers of reproductively viable weevils on high quality plants and use them to supplement field populations after reducing plant biomass using other means (e.g., herbicides or mechanical removal). This could render greater permanency to more traditional control methods. We have developed the means to rear large numbers of weevils on plants grown in outdoor tanks but hand removal weevils from live plants is a slow, tedious process. We therefore developed a simple, efficient method of extracting the weevils by submerging the plants and collecting the weevils as they surface. About 93% of the resident weevils are recovered within 3 hrs. Most come to the surface within 10 min and 90% surface within 30 min. Thus, large numbers can be produced and easily collected to augment poorly performing field populations.

Technical Abstract: The weevils Neochetina eichhorniae Warner and N. bruchi Hustache were released in Florida during 1972 and 1974, to control the floating weed waterhyacinth. Populations established readily but results were variable, with excellent control produced in some cases whereas poor control was manifested in others. We have been examining the relationship between weevils and plant quality over the past few years to investigate this and have found that poor host quality (i.e., low tissue N levels) seems the most likely explanation for low weevil populations and the failure to achieve adequate control in some areas. One approach to overcoming this difficulty might therefore be to mass rear large numbers of reproductively viable weevils on high quality plants and use them to supplement field populations after reducing plant biomass using other means (e.g., herbicides or mechanical removal). This could render greater permanency to more traditional control methods. We have developed the means to rear large numbers of weevils on plants grown in outdoor tanks but hand removal weevils from live plants is a slow, tedious process. We therefore developed a simple, efficient method of extracting the weevils by submerging the plants and collecting the weevils from floating Styrofoam sheets as they surface. About 93% of the resident weevils were recovered within 3 hrs. Most surfaced with 10 min and 90% surfaced within 30 min.