EFFECT OF THE HOST PLANT ON SUSCEPTIBILITY OF THE TWO-SPOTTED SPIDER MITE, Tetranychus urticae KOCH, (ACARI: TETRANYCHIDAE) TO SOME ACARICIDES

The two-spotted spider mites, Tetranychus urticae Koch, reared on kidney bean plants were moved to eggplant, cucumber and new kidney bean plants (the latter being as control) and estimated after one month for changes in susceptibility to some acaricides and in levels of some related detoxification enzymes.
The largest consistent changes were observed in mites feeding on eggplant and cucumber. Susceptibility of mites on kidney bean were significantly more than susceptibility of mites on eggplant and cucumber after feeding on the respective hosts to the all tested acaricides. The LC₅₀ values of mites that feeding on kidney bean plants were 12.3, 35.9, 76.1, 56.6, and 6.7 mg/L. for the tested acaricides; abamectin, dicofol, dinobutone, ethion, and fenbropathrin, respectively. Whereas, it were 32.5, 190.8, 247.3,192.1, and 21.5 mg/L. to mites that feeding on eggplant and 21.7, 279.4, 297.5, 215.3, and 10.5 mg/L. to mites that feeding on cucumber plans for the same above tested acaricides, respectively. 
Susceptibility was inversely related to activities of both general esterase and glutathione-S-transferase (GST) in mites on eggplant and cucumber; general esterase and GST activities were (1.9 to 3.1-fold) and (2.7 to 3.5-fold), respectively, than their activities of mites feeding on kidney bean. Both of the enzyme groups examined, general esterases and GST appeared to be involved in the changes in susceptibility and play a role in the detoxification of the two-spotted spider mite to the all tested acaricides.
Thus, plant-induced changes in general esterase activity in combination with GST activity; in the two-spotted spider mite appear to be possibly responsible for changes in susceptibility of the two-spotted spider mite to several acaricides. In addition to probably allelochemicals associated with host plant may induce changes in the general detoxification enzymes of spider mites.
These changes may have a significant impact on the ability to control spider mites with some acaricides. Better understanding of the biochemical interactions between the two-spotted spider mite and the host plants will need to develop better IPM programs on different hosts.