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Areas in Argentina, Bolivia, Brazil and Paraguay were searched for the cassava mealybug, Phenacoccus manihoti Matile-Ferrero. The mealybug was located in the Paraguay River basin in the Santa Cruz de la Sierra area of eastern Bolivia, the Mato Grosso do Sul state in South-Western Brazil and in Paraguay east of the Paraguay River. Mealybug populations were extremely low in all areas but there was a period of increase from August to December. Eighteen species of natural enemies were found attacking P. manihoti: the most abundant and also most important were a solitary, internal parasitoid, Epidinocarsis lopezi (DeSantis) (Hymenoptera: Encyrtidae), Hyperaspis notata Mulsant and Diomus spp. (Coleoptera: Coccinellidae), and Ocyptamus spp. (Diptera: Syrphidae). Collections of a closely related mealybug, Phenacoccus herreni Cox & Williams yielded two additional encyrtid parasitoids, Epidinocarsis diversicornis (Howard) and Aenasius sp. nr vexans Kerrich, but they did not survive on P. manihoti. Four parasitoids (£. lopezi, E. diversicornis, Parapyrus manihoti Noyes and Allotropa sp.) and four predators (H. notata, Diomus sp., Sympherobius maculipennis Kimmins, and Exochomus sp.) were sent for quarantine. With the exception of Parapyrus manihoti, all mentioned natural enemy species were forwarded to the International Institute of Tropical Agriculture at Ibadan, Nigeria for mass rearing and subsequent release.

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This study assessed the potential economic impact of the introduction of Diadegma semiclausum, an exotic parasitoid of the diamondback moth (Plutella xylostella, DBM), on cabbage production in Kenya. The study first established yield losses caused by DBM through two methods: measurements from farmer-managed fields and through farmers' interviews. Crop losses were calculated at 31% from farmer-managed fields, and at 36% from farmer interviews. With a crop loss of 31%, yield loss was estimated at 6.8 tons/ha or US$ 452.9/ha, and at US$ 7.9 million per year for the whole country. Control costs as provided from the interviews, amounted to US$ 118.9/ha. The project costs amount to a net present value of US$ 1.2 million. Based on an annual cabbage production of 256,524 tons, a cabbage price of US$ 66.3/ton, a 30% abatement of yield losses, a 7.9% reduction in cost of production, a supply and a demand elasticity of 0.9 and −1.4 respectively, and an annual increase of consumption of 2.6%, the economic surplus produced by the release of the parasitoid was estimated at US$ 28.3 million for 25 years. Consumers were estimated to get 58% of the benefit and producers 42%. The benefit-cost ratio was estimated at 24:1, with an internal rate of return of 86%, indicating a high return to the investment.

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