The objective of this work was to study the selectivity of the insecticides acephate, deltamethrin, dimethoate, methamidophos, methyl parathion, and pirimicarb to first, second, and third instar nymphs and adults of the predator Doru luteipes (Scudder) (Dermaptera: Forficulidae) in comparison with last instar nymphs of the prey Brevicoryne brassicae (L.) (Hemiptera: Aphididae). Pirimicarb and deltamethrin were highly selective to all developmental stages of D. luteipes; the same was observed with acephate except for first instar nymphs to whom it showed median selectivity. Dimethoate showed median selectivity, but methamidophos and methyl parathion were low selective to the predator. Second and third instar nymphs and adults of D. luteipes were more tolerant to acephate, methyl parathion and pirimicarb than first instar nymphs. First and second instar nymphs showed similar tolerance to deltamethrin, dimethoate and methamidophos. Concentration-response curves for dimethoate (to adults and first and second instar nymphs) and methamidophos (to third instar nymphs) showed steeper slopes indicating an homogeneous response of these developmental stages to these insecticides.
Insecta; Brassicae; cabbage aphid; earwig; insecticide toxicity
