Influence of phenology, defoliation, and Sclerotinia sclerotiorum on regrowth potential of Ranunculus acris

The biomass and carbohydrate availability of the crown of a herbicide-resistant biotype of Ranunculus acris were studied at six phenological stages from pre-to post-flowering. The crown biomass and amounts of available carbohydrate were the least at pre-flowering, and increased during the flowering period. The regenerative potential of the crown of R. acris after infection by Sclerotinia sclerotiorum was studied at four phenological stages. Regeneration was least after treatment at pre-flowering, and greatest after treatment at late-flowering. The effect of repeated defoliation on regrowth, crown biomass, amount of crown available carbohydrate, and vulnerability to S. sclerotiorum, was evaluated. Six-month-old plants regrew after repeated defoliation without depletion of crown biomass or crown available carbohydrate. In contrast, regrowth of two-year-old plants declined after repeated defoliation, and the crown biomass and available carbohydrate reserves were depleted. Repeated defoliation reduced the potential of plants to regenerate following infection by S. sclerotiorum. No period of major reserve depletion was identified for control with S. sclerotiorum, but repeated defoliation before inoculation may provide better control than inoculation alone.