Effects of cucurbitacin A on mobility of Meloidogyne incognita second-stage juveniles

Abstract

Registration authorities of botanical inputs in crude extract form demand that the active ingredients be isolated, identified and efficacy tests on target pests be investigated. Nemarioc-AL phytonematicide, with active ingredient cucurbitacin A, consistently suppress bioactivities of root-knot (Meloidogyne species) nematode, with limited information on the efficacy of its purified active ingredient. The objective of this study was to investigate the effects of cucurbitacin A on mobility of M. incognita second-stage juveniles (J2). Approximately, 450 freshly hatched J2 were exposed to pure cucurbitacin A concentration at 0.00, 0.25, 0.50, 1.00, 1.25, 1.50, 1.75, 2.00, 2.25 and 2.50 μg/ml distilled water, arranged in a completely randomized design, with three replicates. Experimental units were placed in an incubator at 25±2°C for 12-, 24-, 48-and 72-h. After each duration, mobile and immobile J2 were each counted using a stereomicroscope. Cucurbitacin A concentration effects were highly significant on J2 immobility at all four exposure periods, contributing 84, 99, 99 and 99% in total treatment variation of the variable at the respective periods. Relative to untreated control, J2 immobility increased with increasing concentrations in density-dependent growth (DDG) patterns. In conclusion, cucurbitacin A had significant bioactivity effects on mobility of M. incognita J2 and could be one of the bioactivities through which Nemarioc-AL phytonematicide suppressed nematode population densities.