Saturday, January 6, 2018

The dreaded Rose Rosette Disease is here to stay and does not seem likely that it will be leaving anytime soon. What is this disease? How do your roses get it? What should you do if your roses are infected? What can you do to prevent your beautiful roses from getting Rose Rosette Disease?

Rose Rosette Disease is a viral disease that affects the rose’s vascular system, and symptoms show up on the new growth of the rose. Unfortunately, Rose Rosette Virus is fatal, and once a rose is infected it will eventually die. Many roses will live for up to 4 years with this virus. Identifying the virus by recognizing the symptoms is essential and needs to be acted upon immediately to help reduce the spread of the virus. All infected roses must be removed and destroyed immediately. Rose Rosette Virus (RRV), originally found on the wild multiflora rose, is spread by a tiny little mite called an eriophyid mite. These mites cannot fly but can be carried on the wind for quite some distance.

The symptoms of RRV can be confusing but are generally easy to identify. If your rose is exhibiting red or purple new growth that does not change into the normal rich green during the growing season this may indicate you have the virus. Another sign is the new growth will appear to be massed together, have more smaller leaves and the leaves may have a “strap” look to them. We generally call this a “witch’s broom”. Sometimes the cane may be flattened and be a purplish-red color with many buds on it. This can be a sign of herbicide damage also, but it can be ruled out if you know the history of herbicide applications in your yard and your neighbor’s yards. Unfortunately, herbicide vapors and sprays can travel on the wind, and it does not take very much to affect a rose adversely. Remember, if you suspect you have RRV and have ruled out herbicide damage, it is urgent to remove and destroy the rose/roses infected with the virus in order to reduce the spread of the virus.

We have identified three main characters in this tragic drama; the virus, the multiflora rose and the eriophyid mite. If we can eliminate any single character, our roses will be much healthier and will perform with spectacular results. The big problem here is “if” we can control or eliminate one of them. There is one slight little twist to this tale. The multiflora rose may not be found in your neighborhood, the surrounding natural spaces, or even in your state. There may have been, at some point, an infected rose brought into your area or the mites may have come stowed away on other plants or materials. If you have multiflora roses in your area it may be difficult to get rid of them as they are probably native and in great supply in the surrounding natural areas. This brings us to the mite. The tiny eriophyid mite just might be the best and only character to control and eradicate in this tangled web. There are many miticides on the market and for the most part are effective at controlling mites. Timing and a solid schedule of repeated applications of different miticides will, over time, control the mites. There are many downfalls to using miticides, and each of us must weigh the benefits against the risks to make the decision as to whether we use them or not. As with any insect, disease, or other gardening problem, it is important to attack them from multiple fronts and to not solely rely on one tactic to win the battle.

The most effective way to fight RRV is to be vigilant and observe your roses. Be in the garden, keep an eye out for the symptoms and remove and destroy the plants that are infected immediately. Dig them up, doing your best to get all of the roots out, place the rose in a large garbage bag and then place that bag into another bag and take to the dump or place in a sealed garbage can for the sanitation department to pick up and take away. Clean up all debris and dispose of it in a similar fashion. This needs to be done as soon as you see symptoms on any rose. It may seem drastic, but it is the only way to control this disease.

In summary, RRV is a terrible disease to have to deal with. It is always lethal, and if the rose is infected it will not survive. Multiflora rose is the original host and if present in your area will provide inoculum that will infect all roses nearby. The eriophyid mite is the little monster that will infect your plants by moving the virus from one infected plant to the next. They cannot fly but will travel by foot and move to roses that are close by, and they can be carried on the wind for quite some distance. The best way to control this rampant disease is to be vigilant and to destroy any and all roses that have symptoms. Spraying miticides for the mites has its advantages and disadvantages, and it is your choice as to whether you use them or not. They can offer suppression of mites and may help slow down the spread. Using predatory mites is a great idea but not always as effective as we like. Removing multiflora roses from the wild is most likely neither possible nor cost effective. So, again, be in your garden and be aware of the symptoms of RRV. Dig up and destroy infected roses immediately. It is better to get rid of a few infected roses than to try and nurse them through a lethal disease and subject many more roses to the same fate. Always buy roses from a nursery that sells virus-free roses and be a good neighbor and help your friends learn about this dreadful disease that is causing havoc to our beautiful roses.