Toxicological interactions between Spinosad and essential oils on the Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae

CORTEZ VEGA; JOFRE BARUD,; ANDINO; GOMEZ; SEGURA; LOPEZ, LIZA

Congreso; 6th Congress of ALAEQ 2021; 2021

Ceratits capitata is considered one of the most harmful pest species among fruit flies of economic importance. Historically it was controlled with insecticides but these products have negative impacts, such as pest resistance development. The present study aims to evaluate the toxicological interactions between toxic essential oils (EOs) (Baccharis spartioides, Eucalyptus cinerea and Schinus areira) and the bioinsecticide Spinosad on adults of C. capitata, in order to decrease the concentration of active ingredient bioinsecticide and prevent resistance development. We dispensed 2 µl of each tested solution on each fly (EOs doses 10, 25, 50 and 100 µg/insect; Spinosad doses 25, 50, 100, 200 and 400 ng/insect). According to these results we then prepared 4 formulations of mixtures (EO and Spinosad) considering the Loewe additivity model (⅛, ⅙, ¼ and ½). Mortality was recorded after 24, 48 and 72 h of treatment. We calculated lethal dose for 50% of mortality (LD50) and isobolograms were used to determinate toxicological interactions between mixtures of EOs and Spinosad. LD50 at 48 h were: for B. spartioides: 62,48 and 34,76 µg/insect; for E. cinerea: 107,25 and 53,02 µg/insect; for S. areira: 51,25 and 38,11 µg/insect; and for Spinosad: 826,68 and 266,57 ng/insect; for females and males, respectively. Synergistic activity was found for B. spartioides-Spinosad on females and for S. areira-Spinosad on both sexes; whereas antagonistic activity was found for B. spartioides-Spinosad and E. cinerea-Spinosad on males. Finally, additive activity was found for E. cinerea-Spinosad on females. We highlighted that the ½ S. areira-Spinosad ratio registered higher mortality? than the highest dose of the insecticide (400 ng) administered alone. This mixture could be the basis for a new tool or for the integrated pest management of C. capitata.