INSECTICIDAL AND REPLLENET ACTIVITIES OF CITRUS PEEL OILS AGAINST MEALYBUG ICERYA SEYCHELLARUM (WESTWOD)

Abstract

essential oils extracted from peels of five citrus fruit species namely: navel and baladi oranges (Citrus sinensis L.), grapefruit (Citrus paradisi Macfad), lemon (Citrus limon L.) and mandarin (Citrus reticulata Blanco), belonging to family Rutaceae were tested for their insecticidal and repellent activities at three different concentrations (1000, 5000, 10000ppm) against nymphs and adults of mealybug Icerya seychellarum . Also, formulated compounds, navel orange oil (1%), limonene (1%) and two recommended reference products (2% insecticidal soap and 1.5% Super Misrona), were bioassayed against mealybug I. seychellarum. The results revealed that, the oil of navel orange achieved the highest toxicity against nymphs and adults of mealybug I. seychellarum with LC50 values of (406.97, 370.04 ppm), respectively, while, oil of mandarin recorded the lowest toxicity (LC50= 4148.80, 3435.99 ppm), respectively. Navel orange oil (1%) was more potent than limonene (1%) alone, while, limonene (1%) was more potent than the two reference products. Citrus species oils exhibited high repellency rate against the nymphs of I. seychellarum at the used concentrations. The highest repellency was achieved by navel orange oil, while, the lowest one was recorded with mandarin oil. The essential oils of five citrus species were isolated by hydrodistillation and the analysis of essential oil by GC/MS revealed the presence of 32 peaks, approximately all peaks were identified. The chemical composition showed that limonene was the main constituent in the five citrus oils and ranged from 67.50 to 91.20%. No phytotoxic symptoms were observed on Mango leaves treated by the citrus essential oils (Orange and baladi) and limonene. The results of the present study suggested that, orange oils (Navel and baladi) and pure limonene used as safe, potential natural products for control of I. seychellarum on Mango trees and may be used as alternatives to the reference products after application of these results in the semifield and field experiments.