Botanical extracts fromDodonaea viscosa(Sapindales: Sapindaceae) reduce hemocyte counts fromSpodoptera exigua(Lepidoptera: Noctuidae) with potential insecticidal synergism withIsaria fumosorosea(Hypocreales: Cordycipitaceae)

摘要

Some botanical extracts affect the cellular immune system of insects by interfering with normal hemocyte function. This gives rise to diminution in cellular immunity and causes a decrease in insect defense. This investigation evaluated the effect of acetonic (AcEDv) and methanolic (MeEDv) extracts ofDodonaea viscosa(1000, 2000, and 4000 ppm) on the total hemocyte count (THC) present in the hemolymph ofSpodoptera exigua, as well as on its insecticidal activity, on its own and in combination with the entomopathogenic fungusIsaria fumosorosea. Water and Tween (R) were used as negative controls and Lorsban (R) as a positive control. Second instarS. exigualarvae were separately fed an artificial diet incorporating both extracts. THC was significantly lower inAcEDvtreatment at 1000 ppm andMeEDvtreatment at 1000 and 4000 ppm compared with negative controls. The insecticidal action of the individual extracts and those in combination with the conidia ofI. fumosoroseamanifested from day 21, while at day 28, theAcEDvat 1000 and 2000 ppm and theMeEDvat 4000 ppm applied with the fungus revealed mortality percentages higher than 50% and a significantly higher mortality compared with the negative controls. In conclusion, the extracts ofD. viscosareduced the total THC ofS. exiguaand suggest that the application of this plant extract presents a synergistic effect on the mortality ofS. exiguaexposed to entomopathogenic fungusI. fumosorosea.