Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2000
Publication Date: N/A
Citation: N/A Interpretive Summary: The Colorado potato beetle (CPB), an important pest of potato, tomato and eggplant crops, causes hundreds of millions of dollars in crop losses in North America, Europe and other countries throughout the world. Mass releases of the parasitic wasp Edovum puttleri has kept damage (from CPB) to eggplant fields below the economic threshold level and has almost eliminated the need to spray chemical pesticides. However, the cost of producing large numbers of wasps on CPB eggs is high because of the huge numbers of plants required to rear the beetles for egg production. A system in which wasps could be reared on artificial diet would be more cost effective. Our laboratory has developed an artificial diet which will support the growth of the parasitic wasp through the pupal stage, but which requires insect products. In order to improve the diet and to eliminate the need for insect components, this study undertook to identify those amino acids and carbohydrates which would provide a favorable environment for the growth and development of the wasp. The effects of 20 carbohydrates and 13 amino acids were evaluated both singly and in combination. We report here that in the absence of insect components, certain combinations of amino acids and sugars will support the development of E. puttleri through the pupal stage. Our results contribute to the development of a successful, cost effective artificial rearing system for E. puttleri as well as for other insect parasites. In regard to the selection/combination of amino acids and sugars required for parasite development, the field has been considerably narrowed. Of the 13 amino acids tested, only two in combination with five of the 20 carbohydrates tested provided the appropriate medium for parasite pupation.
Technical Abstract: Previous studies have demonstrated that E. puttleri, an egg parasitoid of the Colorado potato beetle, can be reared through the pupal stage in an artificial diet containing either hemolymph from Manduca sexta or CPB embryonic cell line-conditioned medium. In order to improve the diet and reduce production costs, i.e., eliminate the insect-derived components, the eeffects of 13 amino acids and 20 carbohydrates on the growth and development of the parasitoid were determined. In the presence of any one of five of the amino acids (arginine, glutamine, lysine, threonine and valine) at a concentration of 1%, or eight of the carbohydrates (cellobiose, fructose, gentiobiose, glucose, lactose, melinbiose, sorbitol and threhalose), also at a concentration of 1%, more than 75% of the larvae molted to the second instar. Amino acids (each at 3%) or all 20 carbohydrates (each at 3%), 36 and 39%, respectively, of the parasitoids formed prepupae. At lower concentrations, reduced percentages of prepupal formation were observed. Since the amino acids, glutamine and threonine, and the sugars, fructose, gentiobiose, glucose, lactose, sorbitol and trehalose, when added individually to the diet (at a concentration of 3%) were most effective in promoting prepupal formation, the effect of one of these two amino acids in combination with each of the six sugars was tested. Glutamine in combination with lactose or sorbitol was able to promote pupation, and threonine in combination with any one of five of the sugars (lactose or sorbitol were most effective) supported pupal formation. Our study demonstrated that E. puttleri can be successfully reared from the egg through the pupal stage in an artificial diet devoid of insect materials.