Efficacy Of Selected Botanicals And Microbial Agents As Eco-Friendly Protectants Against Fusarium Verticillioides (Sacc.) Nirenberg Ear-Rot Disease Of Maize, Zea Mays L.

ABSTRACT

Fusarium verticillioides is a major fungal pathogen of maize causing rots in seed, root,

stalk and ear; seedling blight and fumonisin mycotoxin contamination of grains. Use of

chemicals is being discouraged due to its human and environmental health hazards.

Information on eco-friendly control method against the pathogen is scanty. Therefore, the

efficacies of selected botanicals and microbial agents as eco-friendly control against F.

verticillioides were determined.

Six Quality Protein Maize (QPM) varieties (ART/98/SW5, ART/98/SW4,

ART/98/SW6, OBATANPA, ILE-1-OB, TZPB) and ACR/99/TZL (local check) were

evaluated in the field to identify susceptible varieties used as seed treatments in two planting

seasons in Randomised Complete Block Design (RCBD) with three replicates. Seedling

Blight (SB), Lodging after Tasselling (LT) and percentage ear-rot at maturity were assessed

using standard procedures. Aqueous extracts of Tithonia diversifolia, Mirabilis jalapa, Senna

occidentalis and Physalis angulata were evaluated in the laboratory in Completely

Randomised Design (CRD) and on field in RCBD for fungicidal activities against F.

verticillioides at 30.0%, 25.0%, 20.0%, 15.0%, 10.0% and 5.0% (w/v). Four microbial agents:

Trichoderma pseudokoningii, T. harzianum, Pseudomonas fluorescens and Bacillus subtillis

were separately bioassayed at four levels of concentration, alongside carbamate in the

laboratory in CRD and the effective levels of concentration were used on the field in RCBD

as protectants against F.verticillioides. ILE-1-OB, ART/98/SW5 and ACR/99/TZL seeds were

treated with S.occidentalis at 10.0% and T. pseudokoningii at 7.1 x 108 spores/mL using three

coating methods [Cooked-cassava Starch Slurry (CSS), Water Suspension (WS) and Powder

Treatment (PT)] were used alongside carbamate (0.5 g/L). Data were taken on mycelial

growth inhibition (%), germination (%) and yield (kg), and subjected to descriptive statistics

and ANOVA at p=0.05.

Variety ART/98/SW5 with 15.0% ear-rot; 13.0% SB and 18.0% LT was rated highly

resistant. Other five varieties had >30.0% LT; >20.0% ear-rot and SB, rated moderately

susceptible. Aqueous S. occidentalis at 10.0% caused most significant mycelial growth

inhibition (20.1%) followed by M. jalapa (16.7%) at 25% concentration. Inhibitory property

of S. occidentalis produced 3.1% yield increase compared with control. Conversely, T.

diversifolia stimulated rather than inhibit mycelial growth of F.verticillioides by 1.9% at

25.0% concentration resulting in yield reduction by 1.4%. Similarly, P. fluorescens at 1.0x109

cfu/mL significantly inhibited mycelial growth by 51.8% followed by T. pseudokoningii at

UNIVERSITY OF IBADAN LIBRARY

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7.1x108 spores/mL by 44.7%; which indicates high inhibitory potential against

F.verticillioides in the field. Carbamate inhibited mycelia by 34.6% and 10.0% yield increase.

Most effective coating method was CSS with significantly lowest incidence of ear-rot (15.0%)

after carbamate (3.2%) followed by WS (20%) and PT (30%). Trichoderma pseudokoningii as

microbial agent had highest effect (18.0%) on maize germination followed by (15.3%) P.

fluorescens, (13.3%) T. harzianum and (1.6%) B. subtilis. Senna occidentalis and M. jalapa

had significant effect of 11.1% and 8.3% respectively on maize germination compared with

control, while T. diversifolia 3.0% and P. angulata 0.9%.

Use of resistant variety-ART/98/SW5, aqueous extract of Senna occidentalis at 10.0%

concentration and Trichoderma pseudokoningii at 7.1x108 spores/mL provided best treatment

of Fusarium verticillioides of ear-rot disease of quality protein maize. These treatments could

be incorporated into integrated management of the pathogen.

Keywords: Quality protein maize, Fusarium verticillioides, ear-rot disease