Evaluation of Repellent Activity of Oils Obtained from the Seeds of Azadirachta indica and Jatropha curcas on the Insect Pest- Aphis craccivora Found in Cowpea

Abstract

Aphis craccivora is one of the major pest of Vigna unguiculata due to its nature of damage caused to this crop. It feeds on all parts of the plant, mostly at the tender stage of the crop. Bioassay was conducted and repeated ten times using live insects, botanicals and an olfactometer which contained the test compound in one arm and the remaining 3 arms served as a control in a four-armed olfactometer in order to determine its effectiveness as a repellent. The treatment odour source contained either 10µL Azadirachta indica or Jatropha curcas oil while the control arms contained no oil and there were tested against adult A. craccivora. The data obtained included the time spent by A. craccivora in the different arms of the olfactometer and the number of visits to each arm. Each of the data was analyzed using paired t-test. Aphis craccivora spent significantly less time in the arm of the olfactometer that contains J. curcas oil (0.11min) than the arms that did not contain the oil (4.06 min). Similarly, A. craccivora spent significantly more time in the arms of the olfactometer that were not treated with oil (4.23 min) than the arm treated with A. indica oil (0.51 min). Also, the number of entries made into the arms treated with J. curcas (0.10 min) and A. indica (0.40 min) were significantly less than the number of entries made by A. craccivora into their respective arms without J. curcas (1.87 min) and A. indica (2.33 min). The results indicated that both oils significantly repelled A. craccivora as less time was spent in the plant oil-treated arms. Similarly, more visits were made by A. craccivora to the control arms. This showed the efficacy of both oil extracts as a repellent to A. craccivora.