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 argentifolii 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 Howard (California) and 3 populations of Eretmocerus mundus Mercet (M92027, M92014, and M93005) responded positively to odors emitted from whitefly-infested foliage, whereas populations of Encarsia formoso Gahan (M93017 and M92030), Eretmocerus staufferi (Rose & Zolnerwich) (M94002), Eretmocerus tejanus (Rose & Zolnerwich) (M94003), and E. mundus (M92019) did not. None of the populations differentiated between odors emitted from poinsettia versus cotton. E. pergandiella located whitefly-infested plants the quickest, followed in decreasing order by E. mundus (M92014), E. formosa (M92030), E. tejanus, and E. mundus (M92019 and M92027). Once within a patch of whitefly, parasitoid functional responses varied significantly among populations and between host plants. Although host feeding, parasitism, and total whitefly killed by each parasitoid population tended to be greater on poinsettia than on cotton, there was no concordance in performance ranks among the 9 parasitoid populations, 3 performance traits, and 2 host plants. The percentage of parasitoids successfully developing to adults was greatest for Encarsia sp. populations compared with Eretmocerus spp. populations independent of host plant. Results from the host habitat and host location studies suggested that E. mundus (M92014) should be relatively effective in suppressing B. argentifolii populations, whereas E. mundus (M92019) should be relatively ineffective. Population level studies conducted in cage enclosures verified these predictions. Releases of E. mundus M92019 significantly reduced whitefly population levels below whitefly population levels observed in the no-release cages. Moreover, releases of E. mundus M92014 significantly reduced whitefly population levels below whitefly densities observed in the E. mundus M92019 release treatments.