Rhubarb is a strong plant, which by just a few diseases kan be attacked, when you are starting the nurserey with healthy parentmaterial.
Spread over the leaf, oval till irragular formed brown spots are present. The disease is starting special under wet conditions and on bad handled parcels. And the attack of this disease can occur a prematurely die off of leaves.
On the upperside of the leaves arise red-like till purple spots, which are white at the underside of the leave and bell shaped. Out of this comes a whity powder(cupspores). This rust exchange from plant to plant. The summer- and winterspores are formed on reed in longformed, brown spots on both sides of the leaf. The cure contains on cutting out reed in time and around planting.
Falsh mildew(Pernospora jaspiana)
On the upperside of the leaves arise yellow-like spots, which are covered on the underside with a white mouldy mycelium. Cool, wet weather stimulates the attack.
In Spring the development of leaves stays backward by those of health plants. Often chlorotic spots are present, but not on all leaves of the sick plant. Something it is just a matter of some yellow little spots, while other leaves are full of spots. Even there can be mozaic-symptoms, too light coloured leaves and necrotic rings or necrotic stops on the leaves been found. Later in spring certain parts of eaves has a poor development. They are lightgreen and weaky. In the summermonths on these places there fall great holes in the leafsytem.