A cage experiment with four trophic levels: cassava plant growth as influenced by cassava mealybug, phenacoccus manihoti, its parasitoid epidinocarsis lopezi, and the hyperparasitoids prochi- loneurus insolitus and chartocerus hyalipennis

Goergen, G. & Neuenschwander, P. (1992). A cage experiment with four trophic levels: cassava plant growth as influenced by cassava mealybug, Phenacoccus manihoti, its parasitoid epidinocarsis lopezi, and the hyperparasitoids Prochiloneurus insolitus and Chartocerus hyalipennis/Käfigversuch mit vier trophischen stufen: Das wachstum von maniok unter dem einfluß der maniokschmierlaus, Phenacoccus manihoti, ihres parasitoiden epidinocarsis lopezi sowie der hyperparasitoiden prochiloneurus insolitus und chartocerus hyalipennis. Zeitschrift für pflanzenkrankheiten und pflanzenschutz/Journal of Plant Diseases and Protection, 99(2), 182-190.

Different combinations of insects belonging to three trophic levels were released in large cages with hydroponie cultures of cassava in a greenhouse. The cassava mealybug (CM)' Phenacoccus manihoti Matile-Ferrero (Horn., Pseudococcidae) was applied at two initial infestation densities to cassava, some of which was grown at different fertilizer levels. Some cages received Epidinocarsis lopezi (De Santis) (Hym., Encyrtidae), the CM specific parasitoid, and/or the hyperparasitoids Prochiloneurus in solitus (Alam) (Hym., Encyrtidae) and Chartocerus hyalipennis Hayat (Hym., Signiphoridae). Plant survival and dry matter production were used to assess the hyperparasitoid's effect via the food chain. All plants infested with CM alone died, while their final dry weight was 34-65 % of the uninfested control. In the presence of E. lopeziy dry matter ranged from59 to 100 % compared to uninfested plants and depending on the initial CM density. Adding either of the hyperparasitoids did not significantly reduce E. lopezi s efficiency in preventing plant damage. In the presence of both hyperparasitoids and at low initial CM infestation levels, however, dry matter was 58 % of the control, and plant survival was reduced from 93 % to 76%. The generally mild impact of hyperparasitoids in the cage experiments confirms results from the field. Verschiedene Kombinationen von Insekten dreier trophischer Stufen wurden in Käfigen mit hydroponischer Maniokkultur freigelassen. Die Maniokschmierlaus (CM) Phenacoccus manihoti Matile-Ferrero (Horn., Pseudococcidae) wurde in zwei Befallsdichten auf Maniok-Pflanzen, welche zum Teil verschie den gedüngt wurden, ausgesetzt. Ein Teil der Käfige wurde mit dem CM-spezifischen Parasitoiden Epidinocarsis lopezi (De Santis) (Hym., Encyrtidae) und/oder den Hyperparasitoiden Prochiloneurus insolitus(Alam) (Hym., Encyrtidae) und Chartocerus hyalipennis Hayat (Hym., Signiphoridae) beset