BIOCONTROL OF BLACK ROT DISEASE OF OKRA WITH Trichoderma harzianum

Abstract

This experiment was conducted using okra (Abelmoschus esculetntus L. Moench) variety (NHAE 47-3) that is high yielding , rich in vitamins and iodine that are essential for body building . However, okra production in Nigeria is negatively affected by some factors of which pest and diseases are major. Macrophomina phaseolina is one of the major pathogens of okra which causes considerable loss by reducing germinability , seedling emergence, black rot disease, wilting and damping-off with resultant damages on seeds , stem, flowers and pods. Studies were carried out to investigate the efficacy of Trichoderma harzianum as seed treatment and foliar treatment in the control of okra disease caused by M. phaseolina. T. harzianum used in this study was isolated from decayed wood obtained from Federal University of Technology Akure, Ondo State, Nigeria and M. phaseolina was isolated from infected okra seeds obtained from National Institute of Horticulture and Research (NIHORT) in Ibadan, Oyo state, Nigeria . Seeds and foliar treatments were s follows T0 = (control),sterile distilled water (C1) and pathogen only (C2),T1 =preventive, seeds treated with T. harzianum (T.H) before introduction of M. phaseolina (M.P) (24, 48 and 72 hours) , T2 = curative, seed treated with M. phaseolina before introduction of T. harzianum (24, 48 and 72 hours) ,foliar application Tt = Sterile distilled water ,T3 = T. harzianum suspension before introduction of M. phaseolina (at 24, 48 and 72 hours respectively), T4 =M. phaseolina suspension before introduction of T. harzianum (at 24, 48 and 72 hours respectively),T5 =Mancozeb suspension before and after introduction of M. phaseolina (at 24 and 72 hours respectively). It was observed from this studies that there were significant variations in all treatments under in-vitro. The antagonist inhibited the mycelial growth of M. phaseolina in all the treatments. The significantly (P< 0.05) highest percentage inhibition was recorded in 72 hours preventive having 92.11% and the least inhibition was recorded in curative having 14.97% at 72 hours . In in-vivo studies, it was observed that the percentage seed germination and seedling establishment with T.H 72 M.P had significantly highest germination of 76.90%. Disease incidence was significantly higher in seeds treated with pathogen alone having 70.25%. Furthermore, disease severity was higher in control with pathogen alone having 71.17%. There was no significant difference in okra flowering as growth progresses due to flower abortion caused by M. phaseolina. Also, it was observed that okra seeds treated with T.H 72 M.P had significantly highest number of pods, 5.55.From this study it was observed that the use of T. harzianum would be more beneficial, environment friendly in okra cultivation and may be used as an alternative to synthetic fungicides to enhance plant growth and reduce disease incidence subsequently, resulting in high okra yield in Nigeria.