Identifying And Treating Rose Mosaic Disease

Rose mosaic disease (RMD) is a common problem affecting many flowers including roses. RMD causes leaves to turn brown or blackish, which may cause them to fall off completely.

Sometimes they die back from the infection entirely. The disease is caused by a fungus called Rhodotorula edodes, which usually infects plants grown in warm climates such as California and Florida where temperatures are hot enough for it to thrive. The disease is not contagious, but it can spread quickly among susceptible plants.

Symptoms Of RMD

The first symptom of RMD is the appearance of small spots on the plant’s leaves. These spots appear as dark brown areas on the leaves and often begin appearing within days after infection occurs.

They become larger over time until they cover most of the affected area with a thin layer of dead tissue. Leaves will eventually drop off completely if left untreated.

The second symptom of RMD is the death of some or all of the leaves. Leaves will die back from infection entirely if left untreated.

If leaves do not fall off completely, they may rot away to nothingness due to lack of oxygen. Once infected, a plant cannot recover naturally unless treated immediately with fungicide. Fungicides are available commercially and are effective against both the spores and the fungi responsible for causing RMD.

Treating RMD

It is not recommended to apply a fungicide until the disease has taken hold, because the application of insecticides or herbicides can make it easier for the disease to take hold in your plants. Once it has infected a plant, it is best to treat it immediately with a fungicide or it will quickly spread to other surrounding plants.

Treating infected plants usually gives good results if done early enough. It is best to apply the fungicide as soon as you notice the first symptoms of RMD.

Identifying And Treating Rose Mosaic Disease - Picture

However, even professional gardeners do not always catch it in time or realize what is wrong with their plants until it is too late to save them. Fungicides are available for purchase at most home and garden stores and are commonly included in ready-to-use spray bottles for small gardens and planters.

Most fungicides are effective against the spores that cause RMD, but will not eliminate the infected leaf tissue already killed by the disease. It is best to trim off all of the infected areas before using a fungicide to prevent cross-contamination to other plants.

If the infection has spread throughout most of the plant, it may be quicker and easier to simply remove and dispose of the infected plant entirely rather than attempting to treat it.

Once the infected area has been cleaned up, apply the fungicide as directed on the product label and water it in well. Be sure not to over-apply the fungicide because this can be harmful to plants and won’t provide any additional benefits against the disease.

Fungicides are usually available in two forms, a liquid and a granular (sometimes called a dust). The liquid form is mixed with water and sprayed on the plants like any other household pesticide. The granular form, which appears as a white powder, is mixed with water and applied to the soil around the plant where it spreads out and drenches the roots of the plant.

Non-chemical, natural methods of protection are also available for those who prefer them. One of the most common is the use of companion plants for repelling insects that carry RMD.

Marigolds and French marigolds have proven to be very effective at preventing many types of insects from coming around, and they are hearty enough to survive most conditions. Creeping buttercup (to be avoided in gardens anyway) is also useful as a natural insect repellent. There are also a few herbs that have proven to be useful, including sage and rue.

Saving Transplants

Clinopodium is an especially important herb in this case because it has been known to kill off insects that carry RMD without harm to humans or most other animals. Because of its great importance as an insect repellent in the garden, it is wise to always have some growing nearby.

Nasturtium is also important in repelling insects and its peppery taste is enough to keep most garden pests away.

Sprays made from comfrey leaves, tansy, or chrysanthemum flowers can also be mixed with water and applied to the leaves of individual plants to create a barrier against many insects, but it has no lasting effect and must be reapplied after a heavy rain.

Garden Maintenance

Identifying And Treating Rose Mosaic Disease - igrowplants.net

The common advice to gardeners with crystal gardens is to try not to spend too much time weeding. This may seem easy for some, but for others it is almost impossible.

A lack of weeding can quickly lead to a jungle-like environment where it is easy for an infected leaf to hide from the gardener until it is too late.

Sources & references used in this article:

A multipartite single-stranded negative-sense RNA virus is the putative agent of fig mosaic disease by T Elbeaino, M Digiaro, A Alabdullah… – Journal of General …, 2009 – microbiologyresearch.org

A novel mite-transmitted virus with a divided RNA genome closely associated with pigeonpea sterility mosaic disease by PL Kumar, AT Jones, DVR Reddy – Phytopathology, 2003 – Am Phytopath Society

An ultrastructural study of fig mosaic by GP Martelli, MA Castellano, R Lafortezza – Phytopathologia Mediterranea, 1993 – JSTOR

Some mosaic diseases of Prunus species by H Thomas, T Rawlins – Hilgardia, 1939 – hilgardia.ucanr.edu

Population dynamics of Bemisia tabaci (Homoptera: Aleyrodidae) parasitoids on cassava mosaic disease–resistant and susceptible varieties by M Otim, DJ Legg, S Kyamanywa… – Biocontrol Science …, 2006 – Taylor & Francis

Isolation and analysis of double-stranded RNA from virus-infected plant and fungal tissue by TJ Morris, JA Dodds – Phytopathology, 1979 – apsnet.org

Lysosomal phospholipase A2 (LPLA2) activity as a diagnostic and therapeutic target for identifying and treating systemic lupus erythematosis by JA Shayman, A Abe, R Kelly, J Kollmeyer… – US Patent …, 2011 – Google Patents

Decreased Susceptibility to Viral Disease of [beta]-1, 3-Glucanase-Deficient Plants Generated by Antisense Transformation. by RS Beffa, RM Hofer, M Thomas, F Meins – The Plant Cell, 1996 – Am Soc Plant Biol

Risk assessment of virus in drinking water by GI Mink – Plant diseases of international importance, 1992 – Prentice Hall New York

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