Abstract:
The Evaluation of Azadiracta indica (Neem), Annona reticulata, (Custard
apple) and Annona squamosa (Sugar apple) under laboratory conditions
showed their potential as antifeedants and insecticides for the control of
Epilachna vigintioctopunctata. Methanol extracts of all three plants elicited
a highly significant reduction in food consumption from the Epilachna larvae.
When compared with the other two plant extracts, .A. squamosa produced a
very strong antifeedant effect on the larvae at all concentrations tested. At
the highest concentration (20.0gll)., none of the larvae consumed leaf disks
treated with A. squamosa extract at all, but all larvae died immediately after
they were introduced to the test medium, indicating a strong contact toxic
effect on the larvae. With all the plants, the food consumption decreased
with the increase of the concentration. Among the three plants tested, A.
squamosa was the most effective against the Epilachna larvae causing
significantly very high mortality even after 24 hours. A. indica extract on the
other hand, elicited a much more delayed toxic action in the larvae. When
treated with extracts of A. indica, a positive relationship was observed
between larval mortality and concentration of extracts and also between
larval mortality and time. Larval mortality increased with the increase of
concentration and also with time. However, no larval deaths were recorded
for 4 days with any concentration tested and 100% mortality was recorded
on the 12thday after treatment at the highest concentration (20.0g/l).
