Physiological selectivity of insecticides from different chemical groups and cuticle thickness of Protonectarina sylveirae (Saussure, 1854) and Brachygastra lecheguana (Latreille, 1824) (Hymenoptera: Vespidae)

The use of insecticides more toxic to pest than to natural enemies may favor the conservation of these beneficial organisms. This study aimed to evaluate the physiological selectivity of insecticides from different chemical groups to Vespidae Protonectarina sylveirae (Saussure, 1854) and Brachygastra lecheguana (Latreille, 1824) and cuticle thickness in order to evaluate the tolerance between the two species to the same insecticides. We immersed maize leaves (10 x 10 cm) in insecticide solution in dose (100%), subdose (50%) and distilled water (control) for 5 seconds. We dried the leaves in the shade and subsequently packed them in Petri dishes. The 20 wasps, per plate, received 10% honey and the plates were closed with fine organza fabric and elasticated. After 24 hours, we evaluated the percentage of dead wasps. Alpha-cypermethrin insecticide was highly toxic to P. sylveirae and B. lecheguana in dose (100%) and subdose (50%). Novaluron, chlorantraniliprole, spinosad and indoxacarb insecticides were poorly toxic to P. sylveirae and B. lecheguana in dose (100%) and subdose (50%). The high toxicity of insecticides methomyl + novaluron, chlorantraniliprole + lambda-cyhalothrin and deltamethrin to P. sylveirae corresponded to a smaller cuticle thickness. Therefore, novaluron, chlorantraniliprole, spinosad and indoxacarb insecticides showed physiological selectivity to P. sylveirae and B. lecheguana.