Effect of aqueous leaf extract of neem (Azadirachta indica) on different age groups of second stage-juveniles of Meloidogyne incognita

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.