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United States Department of Agriculture

Agricultural Research Service

Title: Chemicals Useful for Separating Egg Masses of the Screwworm

Authors
item BERKEBILE, DENNIS
item SKODA, STEVEN

Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2002
Publication Date: September 1, 2002
Citation: Berkebile, D.R., Skoda, S.R. 2002. Chemicals useful for separating egg masses of the screwworm. Southwestern Entomologist. 27: 297-299.

Interpretive Summary: Screwworms are important economic pests of warm-blooded animals, including humans, in the tropical and subtropical regions of the Western Hemisphere. They were one of the most important pests of livestock in the U.S. until the highly successful eradication program eliminated the screwworm from the U.S., Mexico, and most of Central America. Active eradication campaigns against the screwworm are ongoing in the Caribbean and Central America. Also, active exclusion programs exist in the countries where screwworms have been eradicated. The eradication efforts are valuable to the countries where screwworms are still pests and also help to reduce the chances of screwworm becoming reestablished in the U.S. To remain successful, research efforts that enhance the eradication program are essential. Here we used sodium hydroxide solutions to separate screwworm egg masses. We saw no negative impact on embryo survival or egg hatch when egg masses were submerged in 1% or 2% solutions of sodium hydroxide for ten minutes. Separating the egg masses allows easy handling of individual eggs and increases accuracy in monitoring life parameters in screwworm colonies. We now use this technique routinely in our research colonies. The mass rearing facility of the eradication program, that rears hundreds of millions of flies weekly, should be able to use sodium hydroxide to separate egg masses and then more accurately seed eggs to rearing media by using a volumetric dosifier. This technique could save money for the eradication program by enhancing the mass rearing effort, a costly part of the program.

Technical Abstract: The eradication program against screwworms, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae), using the sterile insect technique has been very successful because of continuous research efforts to enhance the efficiency of the program. Here, we evaluated the effectiveness of three concentrations (0.5, 1, and 2%) of sodium hydroxide (NaOH) for separation of screwworm egg masses. The lowest concentration was slower in separating the egg masses and survival of the embryos was not any greater than for those exposed to the 1% or 2% concentrations. The longer the eggs were in a NaOH solution, regardless of concentration, the more detrimental to embryo survival. Eggs that were allowed to incubate for as much as 6 h before treatment with NaOH did not survive better than newly-laid eggs. No difference was found in the hatch of NaOH treated and untreated eggs. Both the eradication program and research program could benefit from this method of separation of egg massees by facilitating the handling of eggs at the mass rearing facility and allowing research to be conducted on individual embryos.

Last Modified: 7/28/2014