How about Cornops aquaticum (Orthoptera: Acriididae) in its native area in Del Plata wetlands? Ecology and biology of a new control agent of water hyacinth

C. FRANCESCHINI; A.J. SOSA; M. WYSIECKI

Buenos Aires

Congreso; Marine & Freshwater Invasive Species: Ecology, Impact and Management; 2016

Cornops aquaticum is a native grasshopper associated with Pontederiaceae, especially waterhyacinth, Eichhornia crassipes. This insect is being studied as a biological control agent of water hyacinth, which has become the most important aquatic weed aroaund the world. The aim of this research was: (a) assess the life cycle of C. aquaticum, to determine the number of nymphal instars of this species; (b) evaluate variation on abundance ant the age structure of C. aquaticum population living on two host plants: E. crassipes and E. azurea; (c) assess the performance and feeding preference of each age category of C. aquaticum in crops and wetland plants in relation to host plant E. crassipes; (d) discuss the risk and benefits of C. aquaticum as a potential biological control agent in the context of ecology an biology of this grasshopper in native areas. Our results showed that males of C. aquaticum had five instars whereas females had five or six instars. Monthly samplings of populations from February 2004 to April 2006 showed that adults were present during all sampling dates, whereas first instar nymphs were absent during the coldest months. Total abundance reached up to 96 captured insect/minute on E. azurea and 61 captured insect/minute on E. crassipes during summer months. Performance feeding test show that most individuals of C. aquaticum had higher survival on E. crassipes. In some non-host plants, high survival of grasshoppers was also observed, except for first instar nymphs. Ovipositions were registered in E. crassipes and in some non-host plants, but only eggs laid in E. crassipes were endophytic and viable. This grasshopper showed high feeding preference to E. crassipes during the choice tests. Our results confirm high specificity of C. aquaticum to E. crasssipes, hence this species has to be used as bio controller of water hyacinth.