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Title: IDENTIFICATION OF THE MOLTING HORMONE OF THE SWEET POTATO (BEMISIA TABACI) AND GREENHOUSE (TRIALEURODES VAPORARIORUM) WHITEFLY.

Author
item Gelman, Dale
item Blackburn, Michael - Mike
item Hu, Jing - Hu

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2004
Publication Date: 1/3/2005
Citation: Gelman, D.B., Blackburn, M.B., Hu, J.S. 2005. Identification of the molting hormone of the sweet potato (bemisia tabaci) and greenhouse (trialeurodes vaporariorum) whitefly.. Journal of Insect Physiology. 2005. v. 51. p.47-53.

Interpretive Summary: Worldwide, sweet potato and greenhouse whiteflies cause billions of dollars in crop losses each year attacking more than 500 different species of plants including food, fiber and ornamental plants. Damage is due to insect feeding on plant juices, the transmission of viruses and the production of honeydew, a sweet, sticky substance that supports the growth of sooty mold. Currently chemical pesticides are used most frequently to limit whitefly damage. The development of pesticide resistance, concern for environmental safety and pesticide-associated destruction of natural enemies has made the reduction of pesticide use a primary goal for agriculture. Considerable emphasis has been placed on the increased use of biological control agents and insect-specific biopesticides. The development of useful biopesticides and of artificial rearing systems for natural enemies, such as insect parasites, require information concerning the nature of hormones that regulate whitefly development and the ways in which these hormones work. This information is seriously lacking. In this study we collected thousands of whiteflies and used very sensitive detection equipment and assays to identify the molting hormone of whiteflies. Based on our results, we believe that the whitefly molting hormone is 20-hydroxyecdysone, a steroid-type molecule. This is the first report concerning the nature of the molting hormone of whiteflies and their homopteran relatives (e.g., plant hoppers, glassy winged sharpshooters and aphids). Information should be useful to scientists studying the regulation of homopteran life functions, tackling the development of artificial rearing systems for whitefly natural enemies and developing effective biopesticides for whitefly control.

Technical Abstract: In order to identify the whitefly molting hormone, whole body extracts of mature 4th instar and newly formed pharate adult Bemisia tabaci (Strain B) and Trialeurodes vaporariorum were prepared and subjected to reverse phase HPLC. Ecdysteroid content of fractions was determined by enzymeimmunoassay. The only detectable ecdysteroids that were present in significant amounts in whitefly extracts were ecdysone and 20-hydroxyecdysone. The concentration of 20-hydroxyecdysone in B. tabaci and T. vaporariorum extracts, respectively, was 40 and 15 times greater than the concentration of ecdysone. The identity of the two ecdysteroids was confirmed by normal phase HPLC. When ecdysteroid content of RPHPLC fractions was assayed by RIA, small amounts of polar ecdysteroids were also detected indicating that these ecdysteroids have a very low affinity for the antiserum used in the EIA. Although ecdysteroid administered by feeding did not stimulate whiteflies to molt, based on our results, it is exceedingly likely that 20-hydroxyecdysone is the whitefly molting hormone