Optimising Field-Scale Control Of Fusarium Basal Rot And White Rot Of Onion Using Trichoderma Amended Substrates And Pellets, And Onion Residues

• Pelleted bulb onion seed with high populations of spores (>106 g pellet) of the biocontrol agents HDC F37, HDC F39, HDC F41 and Prestop was produced by Incotec/Elsoms
• HDC F37 sprayed at drilling at 0.5 g/m2 significantly reduced the level of white rot but did not suppress Fusarium basal rot; seed pellets containing HDC F37 also showed some reduction in white rot but the effect was not statistically significant
• Serenade ASO drenched at 2 g/m2 was ineffective in suppressing Fusarium but the level of white rot was lower in plots treated with Serenade ASO at this rate
• White rot was consistently controlled in pot experiments using compost + HDC F35 when the soil biocontrol propagule count was increased to 106 cfu/g
• Mechanised application of dried compost + HDC F35 along the planting row at 12 t/ha increased the soil biocontrol propagule count to 3.6 x 106 cfu/g; due to a low level of white rot in the field, the effect on disease could not be established.

Onion white rot (Sclerotium cepivorum) and Fusarium basal rot (Fusarium oxysporum f.sp. cepae) result in economically damaging impacts in bulb and salad onions.  This project aimed to investigate the potential benefits of a range of biological products and crop residues to either improve the microbial community in crop soils, or impact on the germination of sclerotia. 

• Evaluate control of Fusarium basal rot and white rot of onion using substrates and/or pellet carriers amended with specific biocontrol agents and other commercial biopesticides in pot experiments.
• Test the best biocontrol agent substrate and pellet carriers within planting row applications in the field, and establish any independent effects of the substrate carriers on the crop.
• Compare disease control achieved with the biological methods, chemical fungicide treatments, and combinations of biological and fungicide treatments.