RESPONSE OF SUSCEPTIBLE AND RESISTANT PEACH-POTATO APHIDS MYZUS-PERSICAE (SULZ) TO INSECTICIDES IN LEAF-DIP BIOASSAYS

The response of susceptible (S), moderately resistant (R1) and strongly resistant (R2) peach‐potato aphids, Myzus persicae (Sulz.) to organophosphorus, carbamate and pyrethroid insecticides was tested by a leaf‐dip bioassay. The aphids were placed on potato leaves (dipped in insecticide solutions 1–2 or 24 h before infestation) and their mortality examined 48 h later. R1 aphids were virtually susceptible to most of the carbamates, demephion and acephate, but were slightly to moderately resistant (2.1–9.4 times) to permethrin, cypermethrin and (S)‐α‐cyano‐3‐phenoxybenzyl (1R)‐cis‐3‐(2,2‐dibromovinyl)‐2,2‐dimethylcyclopropanecarboxylate (I), (NRDC 161), to 5,6,7,8‐tetrahydro‐2‐methylquinolin‐4‐yl dimethylcarbamate (II), (Hoechst 25 682) and demeton‐S‐methyl. R2 aphids resisted more strongly or very strongly (between 65 and 1280 times) the pyrethroids, demeton‐S‐methyl (×94), II (×83) and demephion (×9), and were slightly to moderately (2–5 times) resistant to acephate, pirimicarb, ethiofencarb and 2‐(dimethylcarbamoyloxyimino)‐3‐methoxyimino‐N,N‐ dimethylbutyramide (III), (DPX 3853). Both resistant strains were susceptible to nitrilacarb [4,4‐dimethyl‐5‐(methylcarbamoyloxyimino)pentanenitrile] complex (1:1) with zinc chloride (IV), (AC 85 258). The implications of these results in terms of practical aphid control are discussed. Copyright © 1978 John Wiley & Sons, Ltd