The red palm weevil (RPW) Rhynchophorus ferrugineus is a
main pest of date palm in a number of the Arabian Gulf States which
includes Saudi Arabia. This work aimed to evaluate the efficacy of nano
chitosan and Spinosad against mortality, some biological aspects, some
enzymes & histological, different haemocyte counts and total haemocyte
counts of 9th instar larvae of R. ferrugineus.
Nano chitosan and Spinosad concentrations of (0.5, 0.1 and 0.05
%) had been tested against these mentioned insects' 9th instar larvae at
different exposure times ranging from 1 to 7 days. The mortality
percentage increased with the increase in exposure times at all tested
concentrations. The results revealed that LC50 (0.11) for nano chitosan
and (0.30) for Spinosad.
Nano chitosan affects some biological aspects of R. ferrugineus
as it led to an increase in the longevity of larvae, pupa and adults (male
and female). The female didn’t put any eggs so, the sterility was 100%
compared with Spinosad and control.
Nano chitosan decreased changes in enzyme activity of ALP,
PO, GPT and GOT recorded (-13.31, -20.88, -10.02 and -35.0%),
respectively compared with control. Spinosad decreased changes in
enzyme activity of ALP was recorded -35.62% compared with control.
While it increased changes in enzyme activity of PO, GPT and GOT
were recorded (40.79, 45.05 and 21.43%), respectively compared with
the control. As well as, nano chitosan and Spinosad decreased the total
protein and total carbohydrates recorded (13.3, 11.67 and 9.03, 10.66
mg/g.b.w.) respectively, in comparison to the control (20.4 and 13.13
mg/g.b.w.), respectively. Results showed that treating 9th instar larvae of
R. ferrugineus with nano chitosan and Spinosad significantly decreased
different haemocyte counts and total haemocyte counts when compared
to the control. Also, appeared some abnormalities in haemolymph cell
morphology.
The histological changes in the midgut of the 9th instar larvae of
R. ferrugineus showed great abnormalities and destruction compared
with the control.