Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 9, 2000
Publication Date: N/A
Interpretive Summary: The Colorado potato beetle (CPB) is an important pest of potato, tomato and eggplant crops in North America, Europe and other countries throughout the world. Each year beetle activity costs growers hundreds of millions of dollars. Mass release of the parasitic wasp, Edovum puttleri, in New Jersey eggplant fields prevented CPB damage. and eliminated the need for additional pesticide application. In addition, the eggplant fruit harvested was superior to that produced in fields which had been treated with chemical pesticides. However, the high cost associated with mass producing parasites on CPB eggs has prevented the effective use of this biological control agent. Development of an artificial diet composed of relatively low cost ingredients would help to alleviate this problem. In this study, the nature and concentration of amino acids and molting hormone in the Colorado potato beetle egg was determined. Physiologically-active molting hormone and its immediate precursor were found to be present at lo levels in 0 48 hour-old eggs, eggs which are preferred by the parasite. Of the nine amino acids present in significant quantities in these eggs, histidine, glutamine and proline were most prevalent. It is likely that the concentrations of amino acids and molting hormone reported here would be ideal for supporting the development of E. puttleri. Our results will contribute to the creation and utilization of a cost-effective rearing system for the parasitic wasp and will also be useful in designing artificial diets for predators and parasites that feed on eggs of pest beetles.
Technical Abstract: In order to identify components of the Colorado potato beetle egg which may be required by E. puttleri (a parasitic wasp that parasitizes the egg stage of the CPB) to complete development, ecdysteroid and amino acid content of CPB eggs were analyzed. Ecdysteroid titers were relatively low through day 2 post-oviposition and then increased sharply on day 3 post-oviposition. E Eand 20HE were the only prominent ecdysteroids present in eggs sampled on days 0 and 1 post-ecdysis, and E, 20HE and 3 peaks containing more polar ecdysteroids (metabolic inactivation products) were present in eggs sampled on day 2. Thus, at a time when parasitization of CPB eggs by E. puttleri is relatively high (0-48 h), physiologically-active ecdysteroid is present at concentrations between 50 and 200 pg/egg. Ecdysone and 20HE reached their highest levels in day-3 eggs indicating that CPB embryos probably synthesize ecdysteroid which is required for the beetle to complete embryonic development. Regarding amino acid composition of CPB eggs, nine amino acids (histidine, glutamine, proline, asparagine, serine, glutamic acid, threonine, lysine and tyrosine) were present in significant quantities in eggs sampled at various times between 0 and 48 h post- oviposition. The first three amino acids were present at concentrations that were approximately two - six times greater than the concentrations of the last six amino acids. This is the first report concerning the concentrations of ecdysteroids and amino acids in beetle eggs in general and CPB eggs in particular, information which should facilitate the development of diets for both parasites and predators of pest species of beetles.