The intensive use of agricultural soils reveals the massive
application of agrochemicals. There is no follow-up of the
presence of pesticide residues in soil or their toxic effects
on organisms that are beneficial for agrosystems, such
as earthworms (
Lumbricus terrestris
L.) The objective
of this study was to evaluate the effect of pesticides used
in horticultural orchards on earthworms, and the use of
earthworms as an indicator through carboxylesterase (CbE)
activity, which is an enzyme involved in the detoxification
metabolism of organophosphorus, carbamates, and
pyrethroids. Eight individuals were place in each
polyethylene container and the container were buried
under the soil surface in two apple orchards, one
under organic management and the other under
conventional management. The experiment was carried
out in triplicate. A control treatment was conducted in the
laboratory. The experiment was repeated in autumn, winter,
spring, and summer of the 2014-2015 study period. Three
internal gut tissues of the earthworm were measured for
CbE activity in the laboratory. Results showed higher CbE
activity in the crop-gizzard of the control treatment with
14.22 ± 1.00
μmol min
-1 mg
-1 in winter; the lowest activity
was recorded in soil under conventional management in
summer with 6.15 ± 2.77 μmol min
-1 mg
-1 (p ≤ 0.05). There
was a seasonal difference in enzymatic activity that was
higher in winter and autumn with 14.22 and 13.93 μmol
min
-1 mg
-1, respectively, and lower in summer and spring
with 6.15 and 6.31
μmol min
-1 mg
-1 (p ≤ 0.05), respectively;
enzymatic activity was associated with higher pesticide
application. It can be concluded that CbE activity is sensitive
to the inhibitory action of pesticides and can therefore be
used as a biological indicator of agrochemicals.
