Effects of essential oils from the Brazilian pepper tree, eucalyptus and citronella on brassica aphids Brevicoryne brassicae and Myzus persicae (Hemiptera: Aphididae) and their parasitoid Diaeretiella rapae (Hymenoptera: Braconidae)

Abstract

Essential oils (EOs) are alternatives to synthetic insecticides used to control aphids that attack brassica species. However, the effects of species such as the Brazilian pepper tree (BPEO) Schinus terebinthifolius (Raddi), lemon eucalyptus tree (LEEO) Eucalyptus citrio-dora (Hook), and citronella grass (CGEO) Cymbopogon winterianus (Jowitt) on these organisms, as well as on beneficial insects, has been poorly studied. This work was aimed to evaluate the activity of BPEO, LEEO, and CGEO, at concentrations of 0.5% and 1%, on aphids Brevicoryne brassicae (Linnaeus) and Myzus persicae (Sulzer) (Hemiptera: Aphidi-dae) applied on leaf discs and/or cabbages, as well as the chemotaxic effects on its natural enemy Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae). The results showed that the essential oil of C. winterianus had a higher mortality rate for B. brassicae (100%) (0.5%, 48 h) and M. persicae (98.99%) (1%, 48 h). The average number of aphids (both species) found on cabbage leaf discs treated with 0.5% and 1% of the three essential oils (separately) was always lower than those found on leaf discs treated with water. Essential oils at 1% presented significantly higher mortality rates for B. brassicae and M. persicae than the con-trol treatment. Females of D. rapae were attracted to plants of green cabbage with essential oil (0.5%) of S. terebinthifolius , but did not respond to E. citriodora and were significantly responsive to plants sprayed with water when contrasted with those in the presence of C. winterianus oil.