Abstract:
The effect of aqueous neem leaf extract on the survival of second-stage juveniles at four
different age groups, i.e., one, three, five and seven-day-old, second and the egg
hatchability of Meloidogyne incognita was determined at five concentrations, i.e., standard
concentration (SC) (1.2 (w/v)) and four dilutions, i.e., 20%, 40%, 60% and 80% of S.
Sterile distilled water (SDW) was used as untreated controls and all the treatments and
untreated controls were replicated five times. The J2S at the each age group in 1 ml SDW
were exposed to 1 ml of test extract for 48 h and fourteen days, respectively, at the ambient
temperature (30°C±2).
In untreated controls, 100% mortality was recorded with respect to three age groups of J^s.
The nematicidal potential of aqueous leaf extract of neem varies with tne concentration
tested, age of the juveniles ana their combined effects. The highest mortality 96%, was
detected with one-day-old M. incognita juveniles at the concentration of SC. In addition,
higher juvenile mortalities ranging 75-85%, were recorded at 3-and 5-day-old juveniles at
SC. In general, mortalities of juveniles at all the age groups significantly increased with the
increasing concentration. However, mortalities of juveniles at all the age groups
significantly decreased up to the concentration 60% SC. At all the five concentrations
tested, mortalities of M. incognita juveniles decreased with the increasing age of the
juveniles. At SC, mortality of juveniles significantly decreased with the increasing age of
the juveniles. At 60% ana 80% SC, mortalities in 7-day old juveniles were significantly
lower than one, three and five-day old juveniles. Moreover, at 80% of SC, one day-ola
juveniles had significantly higher mortality compared to the remaining age groups, fn
contrast, at 40% and 20% of SC, no significant differences in juvenile mortalities were
detected among the four age-groups. L C 5 0 values for 1,3 and 5-day old juveniles were
found as 66.5%, 67.72%, and 75% of SC while for the one-day-old juvenfles L C 5 0 value
lied beyond the test concentrations. This study shows the requirement of repeated
applications of aqueous leaf extract of neem for the better management of these nematodes.
