THE BIOLOGY AND CONTROL OF CONIELLA LEAF SPOT OF KENAF, HIBISCUS CANNABINUS L., INDUCED BY CONIELLA MUSAIAENSIS B. SUTTON VAR HIBISCI B. SUTTON

  • : Ms Word, Ms Word Format
  • : 74 Pages
  • : ₦3,000 | $25 | ₵60 | Ksh 2720
  • : 1-5 Chapters
  •  
  • Click to DOWNLOAD Materials

THE BIOLOGY AND CONTROL OF CONIELLA LEAF SPOT OF KENAF, HIBISCUS CANNABINUS L., INDUCED BY CONIELLA MUSAIAENSIS B. SUTTON VAR HIBISCI B. SUTTON

Abstract:

Symptomatological studies and pathogenicity tests confirmed that the Coniella leaf spot of kenaf observed in Mokwa in Nigeria was induced by Coniella musaiaensis B. Sutton var hibisci B.Sutton (IMI NO. 280998 and 2809996). Field survey conducted in the southern Guinea savanna of Nigeria in 1984 indicated that C. musaiaensis induced between 41,5 and 98.2 percent damage to the leaves. Out of 57 kenaf cultivars screened on the field and glasshouse for resistance to the pathogen, only Tianung No.lwas free of the disease, three other cultivars, AMC 108 kenaf, A60-282 and local line 1 exhibited high resistance. The month of May at Mokwa, in the southern Guinea savanna, was the best for planting kenaf to avoid severe disease attack and to obtain high grain and fibre yields Planting as from July resulted in flowering in August(when the day length has fallen), severe attack by the leaf spot disease and low grain and fibre yields. Application of NPK fertilizer increased kenaf growth and fibre yield but increased Coniella leaf spot severity on the crop. Supply of N as sole fertilizer also predisposed kenaf plants to attack by the leaf spot. In both cases, the age of plant at first apprearance of disease symptom was reduced significantly (P = 0.05) when compared with plots where NP and NK fertilizers were used. Supply of NP or NK fertilizers significantly (P = 0.05) delayed the time of disease attack on kenaf, reduced disease severity and increased both grain and fibre yields. In-vitro assessment of four fungicides showed that carbendazim andbenemy1 completely inhibited the mycelial growth of the fungus in agar medium at the commercial dosage and at lower concentrations tested. Calixin M and Mancozeb inhibited mycelial growth in culture only at double the commercial dosage. The four fungicides significantly (P = 0.05) reduced the disease severity when sprayed at twoweekly interval compared with the check that was sprayed with water. There was no significant difference (P = 0.05) in disease severity between kenaf plants sprayed with carbendazim at 7-day and 14-day intervals. There were also no significant differences (P = 0.05) in disease severity when the four fungicides were sprayed at 21—and 28-day intervals when compared with the controls in the two years. Retted fibres from fungicide-treated plots showed that there was no need to spray for Coniella leaf spot control if the ultimate aim of planting kenaf was fibre production, because the check plots gave fibre yields comparable in weight with the sprayed plots. However, it is necessary to spray the plots if grain production is required since the fungicide-treated plots gave significantly (P = 0.05) higher grain yield than the unsprayed plots. Out of the 17 plant species belonging to 9 taxonomic families tested for susceptibility to C. musaiaensis, five species – okra, Abelmeschus esculoentus L.; cotton, Gessypium hirsitum L.; pepper, Capsicum annun L.; and two cultivars of reselle (Hibiscus sabdariffa) were found to be susceptible. H. sabdariffa has been reported earlier as an alternative host of the pathogen while the other plants are being reported for the first time. Based on the interaction in the glasshouse between 9 selected kenaf cultivars (3 resistant, 3 moderately resistant and 3 susceptible) as host differentials and 51 isolates of C. musaiaensis collected from many kenaf growing areas in the southern and northern Guinea savanna zones of Nigeria, six pathogenio groups of the organism were proposed. The immediate implication of this is is that more races of the pathogen are probably existing in Nigeria.

THE BIOLOGY AND CONTROL OF CONIELLA LEAF SPOT OF KENAF, HIBISCUS CANNABINUS L., INDUCED BY CONIELLA MUSAIAENSIS B. SUTTON VAR HIBISCI B. SUTTON

Sharing is caring!

Leave a Reply