Interactions between two biological control agents of Eichhornia crassipes (Mart.) Solms-Laub (Pontederiaceae), the weevil Neochetina eichhornia Hustache (Coleoptera: Curculionidae) and the plant hopper Megamelus scutellaris Berg (Hemiptera: Delphaci

Interactions between two biological control agents of Eichhornia crassipes (Mart.) Solms-Laub (Pontederiaceae), the weevil Neochetina eichhornia Hustache (Coleoptera: Curculionidae) and the plant hopper Megamelus scutellaris Berg (Hemiptera: Delphacidae)
Nomvume PETELA1, Julie A. Coetzee1, Steve Compton2
1Biological Control Research Group, Department of Zoology and Entomology, Rhodes University, Grahamstown
2School of Biology, University of Leeds, Leeds, LS16JT,UK

Interactions between biological control agents may have important consequences for the control of target weeds.  In 2013 Megamelus scutellaris (Ms) was the latest of several biological control agents of water hyacinth released in South Africa.  Little is known about how it will interact with the agents already established, such as the weevil, Neochetina eichhornia (Ne), the most widely established and successful biological control agent of water hyacinth. The purpose of this study was to quantify interactions between the two agents and to record effects of the interaction on the control of water hyacinth under controlled conditions at the Waainek Research Facility at Rhodes University, Grahamstown, South Africa. Plants that had been exposed to extensive herbivory by N. eichhorniae were collected from New Year’s Dam to emulate conditions that the hopper would be exposed to upon release, while insect free plants acted as controls. Different combinations of Ne and Ms were maintained on the plants for 12 weeks, and plant growth and insect damage were recorded. The agents appear to complement each other.  The results will improve the management decisions for water hyacinth in South Africa.