HOST LOCATION AND UTILIZATION BY SELECTED PARASITOIDS OF BEMISIA-ARGENTIFOLII (HOMOPTERA, ALEYRODIDAE) - IMPLICATIONS FOR AUGMENTATIVE BIOLOGICAL-CONTROL

We examined the host-finding capabilities of 5 species of Bemisia arge ntifolii Bellows & Perring parasitoids from 9 geographical localities, and related these capabilities to each population's effectiveness as biological control agents. Responses from olfactometry studies varied significantly among parasitoid populations. Encarsia pergandielle Howa rd (California) and 3 populations of Eretmocerus mundus Mercet (M92027 , M92014, and M93005) responded positively to odors emitted from white fly-infested foliage, whereas populations of Encarsia formoso Gahan (M 93017 and M92030), Eretmocerus staufferi (Rose & Zolnerwich) (M94002), Eretmocerus tejanus (Rose & Zolnerwich) (M94003), and E. mundus (M920 19) did not. None of the populations differentiated between odors emit ted from poinsettia versus cotton. E. pergandiella located whitefly-in fested plants the quickest, followed in decreasing order by E. mundus (M92014), E. formosa (M92030), E. tejanus, and E. mundus (M92019 and M 92027). Once within a patch of whitefly, parasitoid functional respons es varied significantly among populations and between host plants. Alt hough host feeding, parasitism, and total whitefly killed by each para sitoid population tended to be greater on poinsettia than on cotton, t here was no concordance in performance ranks among the 9 parasitoid po pulations, 3 performance traits, and 2 host plants. The percentage of parasitoids successfully developing to adults was greatest for Encarsi a sp. populations compared with Eretmocerus spp. populations independe nt of host plant. Results from the host habitat and host location stud ies suggested that E. mundus (M92014) should be relatively effective i n suppressing B. argentifolii populations, whereas E. mundus (M92019) should be relatively ineffective. Population level studies conducted i n cage enclosures verified these predictions. Releases of E. mundus M9 2019 significantly reduced whitefly population levels below whitefly p opulation levels observed in the no-release cages. Moreover, releases of E. mundus M92014 significantly reduced whitefly population levels b elow whitefly densities observed in the E. mundus M92019 release treat ments.