Case History Trichogramma Wasps

Because Trichogramma wasps are the most widely augmented arthropod natural enemies, they make a good example to study mechanisms by which companies produce and consumers receive biological control products from commercial suppliers. The development and sale of Trichogramma products in western Europe and the U.S. differ dramatically, and provide an interesting comparison, with the European situation serving as a good model for future commercial development of augmentation biological control.

Most Trichogramma used in western Europe are for suppression of the European corn borer, Ostrinia nubilalis (Hubner). Currently, approximately 58,000 ha of corn are treated annually with Trichogramma brassicae Bezdenko, 84% of which is supplied by BIOTOP in Valbonne, France (F. Kabiri, personal communication). In 1998, between 400,000 and 500,000 ha of corn in France were treated with some type of pesticide product for O. nubilalis suppression, approximately 10% (45,000 ha) of which was T. brassicae (F. Kabiri, personal communication). Sales of T. brassicae by BIOTOP have consistently increased each year from 1988, when T. brassicae first appeared on the market in France as a crop protection product.

There are several reasons for this success. High product quality is maintained each year through careful selection and maintenance of founder populations of parasitoids, and sophisticated quality controls are employed throughout the host and parasitoid production process (Frandon et al., 1991; Bigler, 1994). The encapsulated formulation of T. brassicae was registered as a crop protection product with 10 years of efficacy and quality control data available for the registration process (Anonymous, 1988; F. Kabiri, personal communication). A single pest species, O. nubilalis, was targeted initially and efficacy data collected prior to commercial sales demon strated suppression equal to pesticides (Kabiri et al., 1990; Frandon and Kabiri, 1998). Efficacy data is collected annually by BIOTOP and its research partners and release methods have been constantly improved so that consistent suppression of an O. nubilalis generation can now be achieved with a single release rather than the original three releases at a cost that is comparable to pesticides (Kabiri et al., 1990; Frandon and Kabiri, 1998). This efficacy data is advertised publicly, in a manner similar to pesticide products. Distribution of product to customers is tightly controlled by BIOTOP. All orders for T. brassicae within a given season are processed well before the beginning of the season. Prior to product shipment, new customers are provided with extensive technical information on T. brassicae biology, rearing, handling, and release, in order to maximize their understanding of the product, and their chances for success. The company monitors temperature data and O. nubilalis population development in all areas where releases will take place to ensure synchrony between O. nubilalis oviposition and T. brassicae releases. Customers are informed in advance of their delivery and release dates. All material is shipped to customers by overnight delivery in double-boxed Styrofoam containers ice packs, or in refrigerated trucks.

In contrast to the western European situation, an estimated 140,000 to 350,000 ha of various crops are treated with Trichogramma annually in the U.S. (Li, 1994). Trichogramma in the U.S. have traditionally been sold as general parasitoids, often for home garden use, with the target pest commonly listed in supplier catalogs as "caterpillars." Often there is little efficacy data to support the use of Trichogramma, and no efficacy data appears in advertising. For example, one of the target pests Trichogramma sold in the U.S. is the cotton bollworm (usually a mixture of two species, Heliothis virescens (F.) and Helicoverpa zea (Boddie)) (Knutson, 1998). In contrast to most pest/crop combinations for which Trichogramma are sold in the U.S., a considerable amount of field research has been done in cotton to determine appropriate release methodologies and assess efficacy. Results from large-scale Trichogramma releases in cotton have been quite variable, with some suggesting good pest suppression and others indicating poor suppression (e.g., Ables et al., 1979; Jones et al., 1977; Stinner et al., 1974; King et al., 1985). A recent reevaluation of Trichogramma releases in cotton (Suh et al., 1998) demonstrated that even though parasitism significantly increased egg mortality of bollworms, density-dependent mortality in the larval stages compensated for this mortality resulting in no reduction in cotton damage. These authors concluded that the egg stage of bollworms is an inappropriate target for biological control efforts in cotton.

Despite the availability of considerable technical knowledge and institutional support (Leppla and King, 1996), there appears to be little implementation of quality control procedures in U.S. production of Trichogramma. Delivery to customers also is not carefully controlled. Schmidt (1998) reported quality and shipment data for Trichogramma ordered covertly from 12 U.S. suppliers, for H. zea suppression in tomatoes. The average number of days material spent in transit was 2.06 ± 0.64 days. Packaging ranged from padded envelopes to cardboard boxes with newspaper packing to Styrofoam boxes with cold packs. Approximately 41% of shipments contained no product information or instructions, 52% of shipments contained basic information on biology and release, and 7% of shipments contained detailed information on biology, release, host, and general information. Of the 24 shipments sampled for species composition, 46% had a mix of species or had species other than that which was claimed. There was no difference in sex ratio between endemic and insectary-produced Trichogramma. However, there was an approximately 14-fold increase in brachyptery of female Trichogramma in insectary-reared Trichogramma when compared to endemic (field-collected) specimens. Although actual prices ranged from $19.50 to $126.99 per 100,000 Trichogramma (both sexes), when quality parameters were included, the cost to obtain 100,000 releasable macropterous females ranged from $81.37 to $3,694.16.

This example highlights the need for more widespread implementation of well-documented quality control procedures throughout production and delivery of Trichogramma products in the U.S., and the need for strong data to support the use of products prior to their reaching the market. Because consumer awareness of quality and efficacy issues in the U.S. may not be high, it also suggests the need for much more stringent regulation of the U.S. biological control industry, either through a major modification of the current voluntary approach, or legislated through public agencies. Long-term success of the industry may depend on this change.

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