The objective of this work was to study the physiological selectivity of deltamethrin, fenitrothion, malathion, and permethrin to nymphs (third and fifth instars) and adults (females and males) of the predator Podisus rostralis. The insecticides were used in concentrations corresponding to 50 and 100% of the concentration used for control of eucalyptus-defoliating caterpillars. Deltamethrin was selective to third and fifth instar nymphs and adults of the predator (1.94, 0.00 and 7.87% of mortality, respectively). Permethrin was selective in favor of fifth instar nymphs (3.55% of mortality), and showed median selectivity in favor of third instar nymphs and adults of the predator (28.22 and 32.08% of mortality). Malathion was medially selective to fifth instar nymphs (49.38% of mortality), but was not selective to fifth instar nymphs and adults of the predator (95.34 and 88.99% of mortality). Fenitrothion was not selective to any instar of P. rostralis (100% of mortality). The high toxicity of fenitrothion to this predator did not decrease when the lowest concentration was used, but the impact of malathion (to third instar nymphs and adults) and permethrin (to females) of P. rostralis was reduced when these instars were exposed to half of the concentrations of these insecticides. The impact of deltamethrin was not affected by the concentration. Finally, third instar nymphs and adults were less tolerant to malathion and permethrin than fifth instar nymphs of the predator; females of P. rostralis were more tolerant than males to the recommended concentration of malathion and to half permethrin.
Predator bug; deltamethrin; fenitrothion; malathion; permethrin
