Managing ammonia emissions from screwworm larval rearing media

Authors: SAGEL, AGUSTIN - Us Embassy, Panama; Phillips, Pamela; Chaudhury, Muhammad; Skoda, Steven

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2015
Publication Date: 10/14/2015
Citation: Sagel, A., Phillips, P.L., Chaudhury, M.F., Skoda, S.R. 2015. Managing ammonia emissions from screwworm larval rearing media. Journal of Economic Entomology. 109(1):478-483.

Interpretive Summary: Screwworms were one of the most important pest of livestock and other animals, including humans, before they were eradicated from the U.S., Mexico and Central America using the sterile insect technique. The sterile insect technique requires mass production of healthy screwworms that are sterilized and released, leading to eventual elimination of the native population. Protein rich diets required for larval screwworms can lead to ammonia liberation, sometimes at high levels, in the mass production facility. Until recently a gel bulking agent was used for the larval media; this gel adsorbed much of the ammonia. A need to replace the gel with an environmentally ‘friendly’ bulking agent, cellulose fiber, while not increasing ammonia levels led to a series of experiments to develop procedures that reduced ammonia emissions when cellulose fiber is used as the bulking agent in the larval media. Additives of ammonia converting bacteria, potassium permanganate and a Yucca powder extract were evaluated. Ammonia converting bacteria did not work. Addition of Yucca powder extract, potassium permanganate, and a combination of these two additives kept ammonia at similar levels as when larval media was bulked with gel. Potassium permanganate also had sufficient antimicrobial properties that addition of formaldehyde in the diet was not necessary. These results indicate that cellulose fiber, a less expensive and environmentally safe material, can be used as the larval bulking agent to the benefit the overall program.

Technical Abstract: Mass production, sterilization and release of screwworms (Cochliomyia hominivorax (Coquerel)) that were competitive in the field significantly contributed to the successful application of the sterile insect technique for eradication of screwworms from continental North America. Metabolic byproducts resulting from protein rich diets required for larval screwworms lead to ammonia liberation, sometimes at high levels, within the mass rearing facility. Until recently a sodium polyacrylate gel bulking agent was used for the larval media and adsorbed much of the ammonia. A need to replace the gel with an environmentally ‘friendly’ bulking agent, while not increasing ammonia levels in the rearing facility, led to a series of experiments with the objective of developing procedures to reduce ammonia emissions from the larval media bulked with cellulose fiber. Additives of ammonia converting bacteria, potassium permanganate and Yucca schidigera powder extract, previously reported to reduce ammonia levels in organic environments, were evaluated. Ammonia converting bacteria did not have a positive effect. Addition of Yucca schidigera powder extract (~1% of total volume), potassium permanganate (~ 250 ppm), and a combination of these two additives (at these same concentrations) kept ammonia at equivalent levels as when larval media was bulked with gel. Potassium permanganate also had sufficient antimicrobial properties that the use of formaldehyde in the diet was not necessary. Further testing is needed, at a mass rearing level, before full implementation into the screwworm eradication program.