Abstract

Pure (98%) cucurbitacin A, which is active ingredient of Nemarioc-AL phytonematicide, reduced egress and increased mortality of Meloidoygne incognita secondstage juveniles (J2). However, in vitro information on how J2 egress and mortality would respond to Nemarioc-AL phytonematicide had not been documented. The objective of this study was to determine in vitro the response of M. incognita J2 egress and mortality to increasing concentrations of Nemarioc-AL phytonematicide, maximum inhibition concentration and possible reversibility of J2 egress inhibition and mortality when the phytonematicide was diluted. Eggs and freshly hatched J2 of M. incognita were exposed to phytonematicide concentrations of 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5 and 5.0% in distilled water. Three independent experiments with three replications each were conducted in an incubator set at 25±3°C and counts were made at 24, 48 and 72 h exposure periods. Relative to untreated control, J2 egress inhibition and mortality increased with increase in phytonematicide concentration. Relative impact values of J2 egress inhibition and mortality when plotted against increasing phytonematicide concentrations exhibited density-dependent growth (DDG) patterns with the inhibition effects being irreversible. Maximum inhibition concentration for J2 egress could not be established, whereas for J2 mortality it was 3.49%. In conclusion, the irreversible suppressiveness of the product on both nematode developmental stages makes it an ideal alternative in nematode management.