Toxicity Effect of Eucalyptus globulus on Pratylenchus spp. of Zea mays

Abstract

Maize (Zea mays L.) is an important food crop widely consumed in various forms in many parts of the world. Its annual yield is largely hampered by nematode infestation, especially the Pratylenchus spp. Experiments were conducted in a screenhouse and under field conditions to evaluate the toxicity of fractions and essential oil of Eucalyptus globulus (Myrtaceae) against Pratylenchus spp. infecting Zea mays. The phytochemical basis of the plant was partly established using Infrared (IR) spectroscopy, Gas Chromatography– Mass Spectrometry (GC-MS), proton and carbon-13 Nuclear Magnetic Resonance (1H-NMR and 13C NMR) Spectroscopy analysis. Effect of application of plant phytochemicals on the planted maize was also examined in terms of growth rate and survival of Pratylenchus spp. The essential oil (ECSG/EO) exhibited significant (p<0.05) toxicity, reduced nematode population and increased grain yield (6.79 kg) compared to the standard, carbofuran (CBFN) (7.18 kg) The Eucalyptus globulus ethanol extract fractions (ECSG/EtOH) showed moderate effect, while the chopped leaf materials used as soil amendment (ECSG/AMDM) exhibited the least potency among all the treatments. Spectroscopic analysis by GCMS revealed the presence of terpenoids and phenolics as major constituents of E. globulus. The essential oil showed the presence of 1,8-cineole (23.3%), citronella (18.1%), geranial (17.6%), isopulegol (10.4%), myrcene (13.0%), cuminaldehyde (9.1%) and 2-pinene (8.5%) as major constituent. Results obtained in this research revealed that essential oil from Eucalyptus (a bio-nematicide) holds promise as an affordable and environmentally-friendly alternative for nematode control and increased crop yield particularly in maize production.