Induction of resistance in cotton (Gossypium hirsutum) against Helicoverpa armigera and Earias vitella by environmentally safe chemicals

Induced resistance was studied in cotton against bollworm (Helicoverpa armigera Hub.) and spotted bollworm (Earias vitella Fab.) by treating the plants with Salicylic acid, Bion (Benzo (1,2,3) thiadizole-7-carbothioc acid (S) methyl ester) and Jasmonic acid. At flowering stage, a set of plants were sprayed with different concentrations of Salicylic acid (1.0, 1.5 & 2.0 mM) and Bion (0.4, 0.8 & 1.2 mM). The mortality of H. armigera was measured by placing the third instar larva in Petri dishes containing leaves (old & young) from each treatment. At boll formation stage another set of plants were sprayed with Salicylic acid (1.5mM), Bion (0.8mM) and Jasmonic acid (0.1mM) for induced resistance against spotted bollworm (E. vitella). Control plants were sprayed with water only. E. vitella were released on the plants three days after induction treatments and percentage infestation was recorded. Results indicated that Bion and Salicylic acid- induction on H. armigera was systemic (young leaves) and local (old leaves) in cotton plant. Little decrease in spotted bollworm was observed with all the chemicals tested, while decrease on Jasmonic acid treated plants was higher than other treatments. There is need for detailed studies with biochemical analysis of defense compounds accumulated or produced after induction treatments.