7 common diseases and pests on rhubarb

The robust rhubarb plant is usually not afflicted by diseases or pests, especially if the care is right. If there are changes in the plant, it could be a fungal attack from too much ambient humidity. However, viruses that occur specifically on Rheum rhabarbarum can also trigger a disease, the rhubarb mosaic virus. Finally, the downy mildew should be mentioned among the diseases, which can also infect the rhubarb in the garden. Pests such as aphids, which in turn promote disease, cutworms or voles can also affect the rhubarb in individual cases and cause a lot of damage.

leaf spot diseases

Leaf spot diseases, which can affect not only rhubarb but also other plants in the garden, include three pathogen fungi. These fungi can overwinter in the soil under the plants on the remains of the plants that were already diseased from the previous year. As early as spring, the new shoots come into contact with the fungal spores again and these settle directly on the leaves near the ground and can thus spread further through rain and wind. The three types of fungi cause the following damage:

• Ascochyta rhei
• mosaic pattern at the beginning
• later brown-red, merging spots
• Spot center dries up over time
• Puccinia phragmitis
• red swellings on leaf undersides
• can be transferred from reeds to rhubarb
• Ramularia rhei
• covers the entire surface of the leaf
• brown to reddish round spots

Fungicides should always be used against the fungal attack of leaf spot disease. The soil and the plant are treated equally. It is also helpful with this disease on rhubarb to generously remove and dispose of the soil. As a preventative measure, no plant remains should be left on the ground over the winter.

Downy mildew (Plasmopara viticola)

Downy mildew always occurs when it is too humid. Therefore, the top priority is not to plant the rhubarb plants too close together, but to spread them generously in the bed. Then fallen rain can dry faster on the leaves. Downy mildew manifests itself as follows:

• yellow to brown spots on the upper side of the leaf
• gray fungal mycelium on leaf underside
• white-grey coating
• leaves yellowed over time

Here it only helps to remove the affected leaves, if necessary, the entire plant and dispose of it in the residual waste. If the plants are too close together, they should be sealed and plants removed from the rows so that the remaining Rheum rhabarbarum can dry out better.

Rhabarbermosaik-Virus (Arabis mosaic Virus)

The rhubarb mosaic virus is actually a variety of viruses that can appear on the rhubarb at the same time. These include the tobacco mosaic virus, the cucumber mosaic virus and also the beet mosaic virus and other viruses. Therefore, the symptoms of the rhubarb mosaic virus are not always the same. Transmission usually occurs via aphids or other insects. The seeds are often affected as well. It is not possible to combat the virus, but insecticides can be used to prevent the disease from being transmitted to the rhubarb in the first place. The rhubarb mosaic virus manifests itself as follows:

• light or dark green spots in spring
• brown discolouration along the edges
• turn into mosaic-like, yellow discolorations
• slight bulges and brown necroses
• different types of damage depending on the virus

If the first signs of damage appear, you should clear the entire bed immediately, the plants can then no longer be saved and have to go into the residual waste. If the clearing does not happen, the viruses can quickly spread to other plants in the garden.

Aphids (Aphidoidea)

Aphids like to appear on the rhubarb plants, especially after a mild winter it can become a plague. If the first pests are detected on the plants, immediate action should be taken. However, since Rheum rhabarbarum is food, insecticides should be avoided. It is better to wash the aphids well off the leaves and then spray the plants with a vinegar-water mixture. This should be done for the following reasons:

• Aphids transmit viruses
• the rhubarb mosaic virus can be transmitted
• Plants are then no longer suitable for consumption
• the harvest fails that year

Wireworms – click beetle family (Elateridae)

Wireworms are the larvae of click beetles. These develop over a period of three to five years. The wireworms feel particularly comfortable in densely overgrown soil and eat dead plant material here as well as the roots of the rhubarb plants. In this case, too, it makes sense not to place the plants too close together and, above all, to regularly remove weeds from the soil. This deprives the larvae of their habitat. The pests cause the following damage:

• entire plant dies
• gets no more water and no nutrients
• Larvae feed on the roots

Cutworms – larvae of the cutworm moth (Noctuidae)

Cutworms are a term used for larvae of the cutworm moth. They like to lay their eggs on the underside of the large rhubarb leaves in spring. The larvae also feed on these. Like the moths, they are only active at night and therefore cannot be seen during the day. The cutworms cause the following damage, not only to Rheum rhabarbarum:

• eat young plants directly at the root neck
• small plants can be destroyed within a few hours
• only one caterpillar is required for this
• occur in dry, warm weather
• strong weeds favor the infestation

Insecticides should not be used against the cutworms. It is better to check the plants, especially the undersides of the leaves, for eggs in a warm, dry spring and remove them immediately. The moths also don’t like water from above, so the plants can be showered off in the evening hours. However, care should be taken to ensure that they can dry well afterwards.

Wühlmäuse (Arvicolinae)

Voles can become a problem in the garden and therefore also with rhubarb. If you have often observed voles in the garden and it is known that they are up to mischief here, you can take targeted action when planting the rhubarb plants. Because the pests feed on the roots of plants in general. If these are protected with a wire mesh basket when planting, the voles cannot reach the roots at all. In addition, the beds can be dug up well in winter or early spring, thus destroying the underground passages.