ABSTRACT

Field and laboratory experiments were conducted between 2017 – 2020 cropping seasons at Vegetable Farm of National Horticultural Research Institute (NIHORT) Mbato Okigwe Outstation, Imo State, Nigeria to study the efficacy of Tephrosia vogelii aqueous and ethanol extracts in the control of Eggplant Fruit and Shoot Borer (EFSB); Leucinodes Orbonalis Guen infesting eggplants. In experiment one, five varieties of eggplant (Solanum gilo, S. macrocarpon, S. ex-lantan, S. aethiopicum, S. melongena) were screened in the field for their susceptibility to EFSB. The treatments were arranged in Randomized Complete Block Design (RCBD) with four replications. Data on adult moth and larval population, length of feeding tunnel, numbers of holes on fruits and shoots were assessed. In experiment two, laboratory studies were carried out to determine the insecticidal properties of eggplant varieties and Gas Chromatography and Mass Spectrum (GC-MS) analysis was used to identify the bioactive volatile compounds of T. vogelii. In experiment three, field control of EFSB on the most susceptible eggplant variety (S. gilo) using T. vogelii extracts (10%w/v, 20%w/v, 30%w/v, 9%v/v, 18%v/v and 27%v/v) and frequency of application  [Once a week (1W), once in two weeks (2W) and Once in three weeks (3W)]was conducted. The experiment was laid out in 8 × 3 factorial fitted into RCBD with three replications. Data on population of adult moth, number of holes on shoots and fruits, fruit yield, percent reductions in yield damage, yield increase and yield damage were assessed. Data collected were subjected to Analysis of Variance (ANOVA) using GenStat Software Programme (2010). Significant means were compared with Least Significance Difference (LSD) at P ≤ 0.05. Results showed that population of L. orbonalis adult moth infestation peaked (16.15) in September. S. gilo was the most susceptible eggplant variety with 32.10 % larval infestation. Phytochemical analysis revealed that S. gilo had lowest concentrations of flavonoids, alkaloids, saponins, glycoside, tannin except steroid which was found in high concentrations. The GC-MS analysis of T. vogelii identified 58 bioactive volatile compounds with Benzene, 1,3-bis (2,2-dimethylpropyl), 2,4,5,6-tetramethyl- (19.78 %), Benzo(c)carbazole (6.98%), 7-Oxabicyclo (4.1.0) heptane, 3-Oxiranyl- (6.1 %) as some of predominant compounds. Once a week (1wk) application of treatments have significant effect (P≤0.05) on percent reduction in numbers of holes, damage fruits and uninfested shoots in the first and second cropping seasons. Highest yield (1.6t/ha) was obtained in plots treated to 1W application.