Physic nut (Jatropha curcas) oil as a protectant against field insect pests of cowpea in Sudano-Sahelian cropping systems uri icon

abstract

  • Cowpea is a profitable food and fodder crop in theSudano-Sahelian region of Africa. Unfortunately, it isextensively damaged in the field by a range of insectpests. The use of locally available insecticidal plantextracts is a promising alternative to chemical cropprotection, which is the most popular managementstrategy but shows many drawbacks. In this respect, oilextracted from seed of the physic nut shrub (Jatrophacurcas) showed promise. The insecticidal properties of J.curcas oil were thus assessed against cowpea insect pestsat the ICRISAT research station, SadorĂ©, Niger. In 2002,four concentrations of physic nut oil extract, formulatedas an emulsifiable concentrate (EC) (namely 2.5%, 5%,7.5% and 10%), were evaluated as field sprays along withan untreated control (water spraying) and a conventionalinsecticide (Deltamethrin Decis® EC) treatment. In2009, these latter two checks were evaluated alongsidefour concentrations of a ?blank? formulation consistingof only the adjuvants of the 2002 EC formulation (namely1.25%, 2.5%, 3.75% and 5%). In 2002, application ofDeltamethrin and physic nut oil at 7.5% gave the highestseed yields, with more than 1000 kg ha-1. Both treatments,alongside the one with 10% oil, sustained significantlylower thrips (Megalurothrips sjostedti) infestation thanthe water-sprayed control. All oil extract treatments andthe Deltamethrin treatment sustained significantly lowerinfestation by Clavigralla tomentosicollis bugs than theuntreated control, with the lowest infestation occurringwith 7.5% oil. Furthermore, correlations between oilconcentration and thrips and bug infestation werenegative and significant, while correlation between oilconcentration and seed yield was not significant, due to aphytotoxic effect of oil at high concentrations. Thefollow-up studies in 2009 confirmed that effects ofJatropha oil on cowpea insect infestation and seed yieldobserved in 2002 could be ascribed to the physic nut oilfraction alone

publication date

  • 2011