Biological control of Bemisia argentifolii (Hemiptera: Aleyrodidae) on poinsettia with inundative releases of Eretmocerus eremicus (Hymenoptera: Aphelinidae):: does varying the weekly release rate affect control?

The effectiveness of varying weekly release rates of the parasitoid Eretmocerus eremicus Rose & Zolnerowich for control of Bemisia argentifolii Bellows & Perring on poinsettias was determined. Two variable release rate strategies for E, eremicus were evaluated: a low-high and a high-low release regimen. In the low-high treatment, one female parasitoid was released per plant per week for seven weeks, then the release rate was increased to five female parasitoids per plant per week for the remaining seven weeks of the trial. In the high-low treatment, five female parasitoids per plant per week were released for the first seven weeks, then the release rate was reduced to one female parasitoid per plant per week for the final seven weeks of the trial. Both release rates averaged three female parasitoids per plant per week. Life-tables were made for B, argentifolii in the presence and absence of parasitoids. In the absence of E, eremicus, egg to adult survivorship for B, argentifolii was 65%. In low-high release greenhouses, average egg to adult survivorship for B. argentifolii was 6% and parasitism was 28%. In high-low greenhouses, average egg to adult survivorship for B. argentifolii was 5% and parasitism was 16%. Average net reproductive rates for B. argentifolii in the absence of parasitoids was 17 indicating a rapidly increasing population. Net reproductive rates were 1.46 and 1.24 for low-high and high-low release greenhouses, respectively, indicating substantially reduced B, argentifolii population growth. At week 14 of the trial, densities of live nymphs and pupae were lower in high-low greenhouses when compared to low-high greenhouses. Better whitefly control is achieved with inundative releases of E. eremicus when this natural enemy acts as a predator as opposed to a parasitoid.