Influence of parasitism by encyrtid parasitoids on the feeding behaviour of the cassava mealybug Phenacoccus herreni

Three encyrtid parasitoids Apoanagyrus (Epidinocarsis) diversicornis, Aenas ius vexans, and Acerophagus coccois (Hymenoptera: Encyrtidae) are used to c ontrol the cassava mealybug Phenacoccus herreni Cox & Williams (Sternorrhyn cha: Pseudococcidae), an important pest of cassava in South America. The in fluence of parasitism on the feeding behaviour of mealybugs was studied by observing honeydew secretion and by the electrical penetration graph techni que (EPG, DC-system). Honeydew secretions were observed after parasitism un til mummy transformation. No strong EPG parameter differences were found be tween parasitised and control insects. All results indicated that parasitis ed mealybugs keep feeding on the phloem sap after parasitism until mummy tr ansformation. The main influence of parasitism on EPG parameters is the app earance of a new pattern resembling the E2 pattern at the extracellular lev el and labelled H. This pattern was also produced with control insects loca ted on an unfavourable feeding site and could be associated with a stress r esponse. It might be related to the still unclear E(c) pattern of aphids. T he relationship of H to stylet activities is discussed.