The Minnesota Northern Gardener magazine was in my mail box today, and there is an article about a new disease showing up in roses in the Midwest ... Minnesota, North and South Dakota, Wisconsin, Iowa, and Illinois. The disease is rampant in southern states because of milder weather.
Rose rosette disease (RRD) is caused by a virus which is carried by a microscopic mite. The tiny, wingless creature is carried by the wind, “ballooning” from plant to plant. The mites crawl inside the petals and scales of rose buds. An infected rose bush produces deformed clumps of rose buds (otherwise known as witches’ broom) with an excessive number of thorns and thick, reddish stems. Leaves can appear mosaic and mottled.
The symptoms resemble those that appear if herbicide has drifted from a nearby yard to your roses. But unlike herbicide damage, roses will not grow out of rose rosette disease.
There is no cure for the virus. The infection will kill a small rose bush in two years. If you allow an infected bush to remain in your garden, you risk the virus spreading to other roses, both yours and your neighbors’. The best solution for home gardeners is learning what the symptoms are, identifying the disease early, and destroying those plants at first symptom. Cut the bush off at the base, dig up the roots and bag it in plastic — get as much as you can.
Trying to save the rose is not smart. Spraying the rose bush weekly with miticides containing bifenthrin (Telstar) or spirotetramat (Kontos) or insecticidal soap may help protect the plants, but that is probably more of an option for commercial growers. And then there is that word “weekly” which means serious commitment.
RRD was confirmed at the Minnesota Arboretum at Chaska last year, so we know what we can expect at some point in the future.
I was just in Farmington last week and noticed the damage caused by Japanese beetles on Linden trees. The tree leaves are skeletonized as a result of the beetles feeding, so from a distance, the trees have a brown appearance. I also noticed them in abundance on the flowers of various roses in the trial gardens we were touring. I have occasionally seen one of these beasts in this area, but their population is still relatively small. The beetle has a rounded body and the greenish color of oil on water ... pretty easy to identify.
I feel like I’m dropping a bomb on our gardening enthusiasm, but I’m included in the battle. If I know what to expect, I can be ready to be proactive in the fight.
On a better note, if your onion tops have kinked over and are getting dry, get those onions out of the ground to prevent neck rot. Also, if the potato vines have died, you want to dig the potatoes soon to prevent them from re-sprouting … that really reduces their keeping quality.