The insecticidal and repellent activities of fruit extracts of
Xylopia aethiopica
(Dunal) A. Rich. and
Dennettia tripetala
(Baker f.) G.E. Schatz belonging to the family Annonaceae was studied against
Sitophilus oryzae
(L.), an economic,
primary post-harvest pest of rice, and other cereal products. Infested rice grains (100 g) treated with 1, 2, 3, 4, and 5%
(w/w) powders of both plants were evaluated for toxicity against
S. oryzae every 24 h for 3 d, and during F
1 progeny
emergence. The essential oils of both plants were also applied at 0.5, 1, 1.5 and 2 mg cm
-2 filter paper in Petri dishes for
toxicity bioassays at 24 h exposure. Repellence bioassay with 10 μL solution of essential oils on filter paper was performed
in a Y-Tube airflow olfactometer. Results indicate that powders of both plants significantly (
P < 0.001) caused adult weevil
mortality and a reduction in F
1 progeny emergence than the control. Essential oils were also significantly (P < 0.001)
adulticidal to
S. oryzae after 24 h with the highest dose (2 mg cm
-2) producing 100% mortality respectively. Similarly,
both male and female weevils significantly avoided the test arm compared to the control arm in the Y-Tube olfactometer
repellence tests. These results suggest that
X. aethiopica and
D. tripetala natural extracts have potential for use as part of
integrated pest management of stored product protection against
S. oryzae.
