Submitted to: Meeting Abstract
Publication Type: Other
Publication Acceptance Date: May 1, 2001
Publication Date: N/A
A precise staging system for tracking the development of, and for identifying physiologically synchronous 3rd and 4th instar/pharate adult greenhouse whiteflies (GHWFs) has been developed. The 3rd instar was divided into eight stages based on body depth, and the 4th instar/pharate adult was divided into nine stages based on body depth and the color and appearance of the developing adult eye. GHWF pharate adult eye and wing development are initiated just prior to the time that the eye pigmentbegins to become diffuse, in Stage-4 and -5 whiteflies, respectively. By Stage 6, wing buds are deeply folded, and by Stage 7, spines were observed on the new cuticle. Whole body ecdysteroid in the levels were high at the beginning of each instar and then decreased in the latter half of the instar (for 4th instars, at Stage 6, i.e., shortly after pharate adult formation). The tiny parasitoid wasp, Encarsia formosa, has been used successfully as a biological control agent to control GHWFs in many countries throughout the world. Wasp development rates differed significantly based upon the whitefly host instar parasitized. Development was fastest and most synchronous when 3rd and 4th instar greenhouse whiteflies were parasitized. In addition, adult wasp longevity was greatest and emergence was most synchronous when these older host instars were selected for oviposition. It is signficant that no matter which GHWF instar ws parasitized, the wasp never molted to its last instar until the host had reached Stage 5 of its 4th instar. Thus, a condition(s) associated with host pharate adult formation appears to be required for the parasitoid's final molt. Results should facilitate the development of artificial rearing systems for E. formosa.