Overuse of synthetic pesticides causes problems for humans and the environment or leads to
insect resistance to insecticides, so plant extracts and essential oils have gained popularity as an
environmentally acceptable alternative to chemical pesticides. This study investigated the toxicity
of Delonix regia leaf and seed extracts, protein patterns, and genetic distance analysis against the
5th instar larvae of cotton leafworm, Spodoptera littoralis Boisaduval. Methanol, petroleum ether,
and acetone extracts of leaves and seeds of D. regia were used to coat castor leaves for ingestion by
the 5th instar of S. littoralis larvae. The seeds’ methanol and petroleum ether extracts were the most
effective (100 and 98 Mortality%), with LC50 values of 0.887 and 1.795 g/L, respectively, 24 h posttreatments.
Data showed that D. regia extracts affected consequences of protein changes compared to
untreated S. littoralis larvae resulted in genetic changes, as well as inhibition of the insect’s important
α-amylases, forming protein complexes, and influencing normal growth and development. GC-MS
analysis of the chemical composition of the seed extract revealed 18 compounds with high levels
of stigmasterol, 2-methyl-4-vinylphenol, benzoic acid, 3-hydroxy, and squalene with percentages
of 43.07%, 21.33%, 14.51%, and 14.12%, respectively. As a result, we concluded that D. regia seed
extracts had the potential to control Spodoptera littoralis larvae.