The aim of the present study was to investigate the effect of three pesticides selection pressure on the protein banding of the
two-spotted spider mite Tetranychus urticae Koch by SDS-PAG electrophoresis comparing. In this experiment, four
batches of mite colonies reared for nine months away from any pesticide contamination were exposed for selection
pressure of the tested pesticides. The first batch was subjected to successive selection with chlorfenapyr, the second
patch was subjected to repeated selection of fenpyroximate, the third one for repeated selection of hexythiazox, whereas
the 4th patch was left without any pesticide treatment as a check. Selection pressure was carried out at LC50 level of
each of the tested toxicant. The selection was studied for 12 generations to follow up the development of resistance and
the resistance ratio (RR) values were calculated. The highest RR value of F12 selected generation was for
Fenpyroximate (14.32) followed by 12.06 for chlorfenapyr, while the lowest value was obtained by hexythiazox (4.22).
Comparing the protein banding pattern of chlorfenapyr fenpyroximate, and hexythiazox resistant strains with the
susceptible one, it was found that the protein bands with MW (54 and 36 KD) appeared only in susceptible strain, while
disappeared in the other tested resistant strains of the two-spotted spider mite T. urticae. The protein band with MW 44
KD was appeared only in Hexythiazox resistant strain. The protein bands with MW 53 and 34 KD were only found in
fenpyroximate resistant strain of T. urticae, whereas such bands were not found in the other strains. The protein bands
pattern with MW 146, 35 and 31 KD were found only in hexythiazox and chlorfenapyr resistant strains of T. urticae.
Such result may indicate that the mechanism of resistance strains is similar for both strains.