The effect of Native Spirulina platensis on the Developmental Biology of Spodoptera littoralis (Boisd)

Spodoptera littoralis is considered to be one of the most dangerous pests that cause a significant reduction in the yield of different economic crops in both open and green house practices. The need for natural pesticides is one of the scientific research goals. The cyanobacterium, Spirulina platensis that proved to be a good source for different bioactive compounds, may be an excellent candidate as a natural pesticide against Spodoptera littoralis. Spirulina bloom that naturally grows in El-Khadra Lake in Wadi El-Natrun, Egypt was isolated and an axenic culture was obtained. The pure culture was identified as Spirulina platensis. The axenic culture was grown in liquid media and maintained at 24-±1 o C under 3000 Lux light intensity. The Spirulina culture yield reached 8.0g wet weight/ L after 15 days. Dried material of Spirulina culture cell content was obtained by ultrasonication and freeze-drying. Dipping solution was prepared using different concentrations of Spirulina culture cell content to test their effect on Spodoptera littoralis. The weight, percent mortality and malformation of larva and pupa were determined. Emergency and malformation of the moths were also observed. The cynobacteria Spirulina platensis cell content showed no significant effect on Spodoptera littoralis larvae at concentrations of 0.5, 1.0, 2.5 mg cell content dry weight / L dipping solutions. However, significant effect was observed on both pupae and moths at these low concentrations. At 5%concentration larval mortality and malformation increased and 100% mortality was obtained.