The susceptibility of Leptinotarsa
decemlineata (Say) adults to spinosad was determined by leaf disk and glass
jar techniques under laboratory conditions. The mortalities of the treated
adults were recorded 72 h post treatments. LC₅₀s values in leaf disk
and glass jar methods for adults were 98.50 and 108.34 mg a.i/L, respectively.  A significant linear relationship between LC₅₀
values of individual population across test methods was detected (r = 0.93,
P < 0.05). Both bioassay
techniques were suitable for monitoring resistance to spinosad in Colorado
potato beetle adult populations. Glass jar technique, however, exhibited less
variability in LC₅₀ estimates and showed a higher degree of
sensitivity than the leaf disk method. Filter paper and leaf disk techniques
for larvae were two bioassay methods used to determine spinosad susceptibility
in L. decemlineata population. Both bioassay techniques exhibited a different
level of susceptibility of the larvae to spinosad; however, the confidence
interval values from filter paper method were narrow than the leaf disk assay
technique. A significant direct relationship between LC₅₀ values of
individual population across test methods was observed (r = 0.96, P < 0.05).  The glass jar and filter paper testing
methods are simple and sensitive test techniques for measuring susceptibility
of Colorado potato beetle adults and larvae to spinosad, respectively. The
efficacy of spinosad can be conserved for a long period of time if it is
judiciously rotated with other suitable insecticides in a spray program and the
number of application is restricted.