Age-related changes in the chemical composition of female pheromone gland of the Egyptian cotton leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae)

Abstract

The Egyptian cotton leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae) is a serious pest that attacks a wide range of crops in Egypt. To relate the age with the chemical composition of the pheromone gland of the female S. littoralis, the chemical components of the gland were analyzed using gas chromatography coupled to mass spectrometry (GC-MS). The pheromone glands of the females were excised at four different ages: newly emerged (D0v), one-day-old (D1v), two-day-old (D2v), three-day-old (D3v) and three-day-old mated females (D3m). Altogether the pheromone glands contained 54 compounds in the hexane extract. The compounds identified were 1 ketone, 1 acetate, 2 fatty acids, 3 esters, 6 aldehydes, 12 alcohols and 29 hydrocarbons. Their presence and relative amounts in the gland varied with age. Few compounds were observed in the glands of D0v, increased in D1v, D2v, and D3v, and remained almost constant in D3m. Fifteen compounds were previously identified as sex pheromone components in other Lepidoptera; the major compounds were the two hydrocarbons, hentriacontane, and heptacosane. Another fifteen components were previously identified from different insect orders other than Lepidoptera. The other twenty-four compounds were identified for the first time in insects. Determination and identification the sex pheromones of S. littoralis may present safe biologically active compounds that could be used in the management programs for this pest in Egypt.