Methods:
Field tests were conducted in 1998 and 1999 to compare the effectiveness of acaricides against spider mites in Arkansas.  The tests were conducted in commercial cotton fields that had heavy spider mite infestations.  Plots were seperated from adjacent plots by 4 rows of cotton on the sides and 15 feet on the ends.  Treatments were arranged in a RCB design with 4 replications.  Acaricides were applied using a 6-nozzle CO2-charged backpack sprayer calibrated to deliver 10.5 gpa at 40 psi with TX-6 nozzles.  For these tests, samples of 10 mainstem leaves, 6 nodes beneath the terminal,  were randomly selected from cotton plants in the center rows of each plot.  A 10x hand lens was used to count the number of mites and eggs in a 1.5 cm2 area of each leaf, to the left of the mid-vein.

Results:
1998:  All acaricides significantly reduced mite numbers at 3 and 7 DAT compared with the water-treated check plots. By 14 DAT mite counts were lowest in the Kelthane and Zephyr plots and mite counts were significantly higher in Curacron-treated plots than check plots. Overall, Kelthane, Zephyr, and Comite all provided good control of spider mites on cotton, with Capture providing intermediate control, and Curacron appearing to flare mite numbers. The data indicate that if spider mites are the only target an acaricide should be used rather than a broad spectrum pesticide.

1999:  All acaricides except Trilogy (neem oil) significantly reduced mite numbers at 3 and 7 DAT compared with the water-treated check plots. The 14 DAT mite counts were made but are difficult to understand.  The grower reported that he had treated the field with Kelthane, but had carefully avoided treating the test area.  There is some evidence that the mite specific fungus, Neozygites floridana, may have wiped out the mite population.  The 14 day data is included, but should not be used to compare the miticides given these uncertainties.  The mite egg data showed no significant differences between miticide treatments by day, and the data provided little useful information.  Overall, Kelthane, Comite, and Zephyr provided excellent control of spider mites on cotton, with Capture providing intermediate control.

Conclusions:
In both tests, the acaricides Kelthane, Comite, and Zephyr provided good control indicating that resistance does not appear to be a problem in Arkansas at present.  It is strongly recommended that acaricides, especially Kelthane, be rotated during a season to reduce the development of resistance in mites.
In California the use of pyrethroids and organophosphates for mite control on cotton is not recommended (2).  They report that these materials frequently result in short-term population reductions followed by rapid resurgence of mite populations that can exceed pretreatment levels.  Because Capture (bifenthrin) is a pyrethroid and Curacron (prophenofos) is an organophosphate, these materials may have a similar effect in Arkansas. These materials should not be used for mite control unless the field is being treated for multiple pests.