Variation in biological parameters of Trichogramma spp. purchased from commercial suppliers in the United States

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The efficacy of biological control obtained through releases of commercially supplied Trichogramma is influenced by both abiotic conditions in the field during and following release and an array of biological attributes of the released Trichogramma. This study was undertaken to assess the degree of variation that existed among commercially supplied Trichogramma in an array of biological parameters that potentially may influence the level of control that can be expected in a Trichogramma release program. Shipments of Trichogramma were obtained from 12 commercial suppliers of beneficial insects over a 2-year period and the following parameters were measured: percentage of emergence during shipping, total percentage of emergence, percentage of females, percentage of brachypterous females, percentage of brachypterous males, adult female longevity, and species composition. In addition, we estimated the percentage of macropterous females that had not emerged prior to the time the shipment was received, based on the first four parameters. Results indicate a high level of variation in each of these parameters among suppliers of Trichogramma and among shipments by individual suppliers. The proportion of non-emerged macropterous female wasps was low for all suppliers (range 2.5–27.7%). This was primarily attributable to the high incidence of brachyptery among female wasps. However, variation among suppliers in the incidence of emergence during shipping and the proportion of female wasps in a shipment also contributed to the low proportion of non-emerged macropterous female wasps. In addition, in 11 of 24 shipments received during the 2-year study, the Trichogramma species differed from that specified by the shipper or the shipment contained a mixture of Trichogramma species.

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