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 a vailable carbohydrate were the least at pre-flowering, and increased d uring the flowering period. The regenerative potential of the crown of R. acris after infection by Sclerotinia sclerotiorum was studied at f our 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 a vailable carbohydrate, and vulnerability to S. sclerotiorum, was evalu ated. Six-month-old plants regrew after repeated defoliation without d epletion 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 deplet ed. Repeated defoliation reduced the potential of plants to regenerate following infection by S. sclerotiorum. No period of major reserve de pletion was identified for control with S. sclerotiorum, but repeated defoliation before inoculation may provide better control than inocula tion alone.