Chemical assessment of seed oil extracted from Rhanterium epapposum Oliv. and its insecticidal efficacy against oleander aphid, Aphis nerii

A biopesticide from the seeds of the most abundant desert plant of the Arabian Peninsula, Rhanterium epapposum Oliv., was attempted in the current investigation against Aphis nerii, a common pest of oleander an ornamental shrub, in laboratory bioassays and its chemical components were profiled through gas chromatography-mass spectroscopy (GC-MS). The oil yielded an average of 2.40 % and its bio efficacy revealed its potency as a bio-pesticide efficient to manage the aphids. While in the bioassay for contact toxicity, the highest concentration of the investigated oil (500 ppm) revealed a 96.70 % mortality on the 3rd day of treatment; in the bioassay for oral toxicity, it was 93.33 %. The trend of mortality was declining for diminishing concentrations of the oil. Further, the toxic regression lines of the highest dose of R. epapposum oil provided the LC50 and LC95 values of 8.67 and 61.78 ppm respectively for oral toxicity and 14.07 and 85.48 ppm respectively for contact toxicity showing the chief toxicity for the highest dosage of R. epapposum oil in aphid management. The GC-MS chromatogram exhibited the existence of 17 compounds with 16 possessing insecticidal properties representing 98.72 % of total oil content, extenuating its efficacy to be formulated as a commercial pest control product. 9, 12-octadecadieonic acid (Z, Z)-methyl ester is the compound detected with the highest percent holding 33.19 % followed by 2-methoxy-4-vinylphenol (29.45 %) and hexadecanoic acid (22.57 %). The safety of the oil for both human health and the environment requires further investigations. The study is a baseline that reflects the insecticidal property of the native treasure of Kuwait, R. epapposum seeds. Further research to isolate the compound affecting the biopesticidal activity and chemo olfactory investigations on the aphids, to sense out the compounds responsible for the toxicity to be formulated as commercial biopesticides is in demand.