If you have an old rhubarb clump in your garden or allotment now is the time to give it your attention. If yields or stick quality have deteriorated it is probably in need of dividing and re-planting. Not only will you once again enjoy better crops, you can increase your stock as well.
It’s an easy process to divide Rhubarb and little finesse is required! Dig the clump and trim back any long adventitious roots. Using a sharp spade, simply chop the clump into 4 or 5 pieces [depending] size. If the clump seems a bit soft in the middle, which may well be the case, just keep the outer sections and discard the centre as it probably won’t grow well. Re-plant into freshly prepared soil [preferably not exactly where the old clump was removed] with a top dressing of bonemeal. Plant with the crowns just level with the soil surface and firm well. This is most important, as is the task of checking on the new plants periodically through the winter to make sure the heaving effects of frost have not loosened them in the soil.
Next Spring make sure they do not dry out whilst establishing so water them during dry spells until about June by which time they should be able to take care of themselves. Resist the urge to pull any stems this first season of re-establishment.
The above notes should help you with rewards like the beautiful healthy clump pictured below; it's Prince Albert - a deliciously flavoured old heirloom variety.
If you feel your Rhubarb may have a disease it’s best to do away with it and re-plant it with good disease-free stock from a specialist grower.