INSECTICIDES USED IN THE TRANSMISSION OF THE RINGSPOT VIRUS OF Carica papaya L., THROUGH Aphis nerii (Boyer de Fonscolombe)

Abstract

The papaya ringspot virus (PRSV-p) is transmitted in a non-persistent way by females of Aphis nerii and other aphid species (Hemiptera: Aphididae). The effectiveness of the application of insecticides to reduce viral transmission has been questioned. Viral transmission tests have been performed with adult females of A. nerii in the laboratory, on papaya plants (Carica papaya). One, two, five and ten winged and wingless female adults of A. nerii were used. The presence of the PRSV-p was determined through the ELISA test. The effect of six insecticides/acaricides with different modes of action was evaluated (malathion, deltamethrin, imidacloprid, fenbutatin oxide, pymetrozine and rotenone), on the viral transmission and mortality of aphids. The products formulated were applied at the lowest recommended dose; later, they to papaya trees were exposed to the inoculating aphids for 24 h. The phytotoxicity was recorded visually in the laboratory. No significant differences were found (p<0.05) in the viral transmission between winged or wingless aphids. The greatest transmission (75 % to 80 %) was obtained with 10 adults and the lowest (15 % to 20 %) with one adult. The significantly lowest transmissions were obtained by using pymetrozine (19 %) and rotenone (29 %), while the highest were with deltamethrin (81 %) and malathion (66 %). Imidacloprid and malathion caused 100 % mortality at 24 h, while pymetrozine and fenbutatin oxide produced the lowest mortality (46 %). Rotenone caused phytotoxicity in papaya leaves. Pymetrozine has potential in the prevention of non-persistent viral transmission.