Diet preference of the different life stages of the aquatic grasshopper Cornops aquaticum (Orthoptera: Acrididae) and its implications for the biological control of water hyacinth

FRANCESCHINI, M.C; HILL, MARTIN; FUENTES-RODRÍGUEZ, DANIELA; GERVAZONI, P.B; SABATER, L.M; COETZEE, JULIE A.

La Plata

Congreso; XI Congreso Argentino y XII Congreso Latinoamericano de Entomología; 2022

SEA

Host specificity determination of weed biological control agents has historically relied on evidencegenerated through quarantine trials in the region of introduction. These trials are conservativeand where possible, more research should be conducted in the region of origin. The oligophagous,semiaquatic grasshopper, Cornops aquaticum (Orthoptera: Acrididae), was released in South Africa forthe biological control of Pontederia crassipes (Pontederiaceae). We conducted post-release laboratoryno-choice trials, using early instar nymphs (instar I and II), later instar nymphs (instar III to VI), adultfemales and males, to determine fundamental host range; and gut analysis from field collected C.aquaticum to determine the ecological host range of this insect. In no-choice trials, survival rates of C.aquaticum were similar on Pistia stratiotes (Araceae), Oxycaryum cubense (Cyperaceae) and P. crassipesfor later stage nymphs and adults. However, under field conditions, P. crassipes and the congenericP. azurea, were the only plant contents in the guts of early instar nymphs and the most abundant onesin later instar nymphs and adults. The results support the evidence that C. aquaticum is an oligophagousinsect in the genus Pontederia, and that life stages should be considered when conducting host-specificitytrials in externally feeding herbivore species. Diet composition of field-collected insects thus providesa better indicator of the field host range.