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Nemarioc-AL and Nemafric-BL phytonematicides consistently reduced populations of plantparasitic nematodes. The contribution of juvenile hatch inhibition to the overall reduction of the nematode numbers by the two phytonematicides, with cucurbitacin A and B as active ingredients, respectively, remains undocumented. The objectives of this study were to examine (i) the response of Meloidogyne incognita second-stage juveniles (J2) hatch to increasing concentration of cucurbitacins A and B, (ii) the potential saturation of J2 hatch when exposed to cucurbitacins for extended incubation periods, (iii) the minimum inhibition concentration for J2 hatch and (iv) the reversibility of J2 hatch inhibition.. Eggs of M. incognita were exposed to a series of purified cucurbitacin A and B concentrations over five incubation periods of 24, 48, 72 h and extended incubation periods of 7 and 10 days. Methanol-dissolved cucurbitacin A and B were each diluted and pipetted into well-plates making 11 concentrations, ranging from 0.0 to 2.5 µg.ml −1 water solvent. Juvenile counts were made after 24, 48 and 72 h, with those for saturation assessed at 7 and 10 days. Thereafter, treatments were diluted five times, incubated again for 5 days and counted to establish reversibility of J2 hatch inhibition. In all incubation periods, treatment effects were highly significant (P ≤ 0.01), with J2 hatch and cucurbitacin concentrations exhibiting quadratic relations. Minimum inhibition concentrations of the two cucurbitacins were between 1.13 and 1.40 µg.ml −1 . Treatment effects for reversibility to J2 hatch inhibition were not significant (P > 0.05). In conclusion, J2 hatch inhibition could be one of the waysthrough which the two phytonematicides reduced population densities of Meloidogyne species. ARTICLE HISTORY

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Informa UK Limited (trading as Taylor & Francis Group) and NISC (Pty) Ltd This is the final version of the article that is published ahead of the print and online issue During the past decade, efforts to develop botanicals as biopesticides have increased (Okwute 2012). As a result, a number of promising biopesticides have been identified (Manju and Sankari Meena 2015). Nonetheless, many issues remain to be solved before these biopesticides can be effectively applied. One of these issues is the claim that the purified active ingredients from botanicals are less effective compared with the fermented crudeextracted biopesticides (Javed et al. 2008;Okwute 2012;Chaudhary et al. 2013). For instance, the Aza formulation, which contains azadirachtin, a purified ingredient from neem seed, showed no effect on the motility and viability, and a lower effect on second-stage juveniles (J2) hatch of root-knot nematode (Meloidogyne species) compared with crude neem cake and leaf extracts (Javed et al. 2008). Grandison (1992 cited by Javed et al. 2008) also did not observe any direct effects of purified substances from neem seed kernels, such as aza, salanine and nimbin, on J2 of Meloidogyne javanica.The first step in determining the bioactivity of plant extracts in most studies consists of in vitro bioassays of purified substances. The inactivity of some of the purified substances resulted in potential phytonematicides failing to move beyond in vitro bioassays, limiting progress in the development of phytonematicides. Okwute (2012) suggested two causes for the observed inactivity of purified substances:(1) less desirable solvents used during purification and