Get a Clean Start on the Growing SeasonRose Disease and Pest Notes: Winter Cleanup
During the cold winter season while the plants are not actively growing is the time to cleanup your rose beds in preparation for the coming growing season. The best way to control diseases and pests that attack your roses is to prevent their occurrence and sanitation in your garden is a key component of such prevention. If you give attention now to some important sanitation measures it will pay off tremendously during the coming season. These measures are the cleanup of rose beds and established roses; and the cleanup of newly acquired rose plants. These sanitation measures will remove likely sources of diseases and pests that can easily be carried over in your garden from the previous growing season or can be brought into your garden on new plants. The removal of old mulch and other plant debris from your rose beds is a first step to prevent the carry-over of disease and pests from the previous growing season. You should rake off all of the old mulch and debris. Then you should bag and discard them. Do not use any rose or rose bed debris for compost, because some disease organisms can survive in this material. When rose bushes are close together a narrow shrub rake is helpful for working between the plants. A great follow-up to the raking is the use a leaf blower to further clean off the surface of your rose beds. For growers who use relatively heavy mulch material such as wood or bark chips and raking is impractical, a leaf blower can be helpful in removing small, loose surface material and rose debris. Established rose bushes should be cleaned up by removing dead or obviously diseased canes, which should be bagged and discarded. Depending on the location of your garden in the South Carolina Lowcountry, your rose bushes may or may not lose their foliage during the winter. If last seasons’ leaves are still attached to the plants, then in order to do the most effective sanitation job, you should remove, bag, and discard them. This can be combined with the removal and disposal of your old mulch. So that wound sites, which could enhance disease development are not created; the old, attached leaves should be clipped off and not torn from the stem. The final step in cleaning up your beds and established roses is the spray application of lime sulfur which acts as something of a disinfectant on the surface of the beds and old plants. These is usually best accomplished after the spring pruning, but before new buds have opened. Both the surface of the beds and the rose plants should be sprayed. This is something of a smelly operation, but is worthwhile because it reduces the survival of both over-wintering disease spores, such as those of the fungus that incites black spot, and over-wintering stages of mite and insect pests, such as red spider mites. (I noticed in the November 2010 Rosemania Newsletter that lime-sulfur has been discontinued and will apparently not be available in the U.S. in the future. I imagine that it may still be available for a limited time until vendors have exhausted their current stock. At this time, I am not aware of a suitable substitute that will be as effective as lime-sulfur for this purpose.) A very important measure to prevent the introduction of diseases and pests from outside sources into your rose garden is the cleanup of newly acquired plants. You should always clean up new plants before they are added to your established rose beds no matter when or where or from whom they are acquired. First, inspect the new plants, then remove, and keep removing, any obviously diseased leaf or stem tissue and keep these new plants isolated some distance away from your established rose beds while their clean-up is accomplished. I keep new plants isolated for at least 3-4 weeks during which time I apply at least three applications of both a protectant fungicide, such as manzate or Dithane M-45, combined with a systemic fungicide, such as Banner Maxx or Cleary’s 3336-F or Compass. During this time, I also apply at least one application of a miticide, such as Avid or Floramite, and one application of an insecticide, such as Orthene or Merit. Accomplishing this isolation measure is made easier because many new rose plants now come in pots. However, you should be sure to provide effective cold protection for these isolated plants. It is very important to keep the soil in these pots from freezing, which is especially deadly for roses on fortuniana rootstock. If your garden is in an area of the South Carolina Lowcountry where the winters are usually mild, to keep your roses in a healthy condition, you should, in addition to the sanitary measures described above, maintain a fungicide spray program. This program should include both a protectant and a systemic fungicide at no longer than 14-day intervals. You can hold off on this program when the weather is severely cold (highs in the 40s and lows below or near freezing), but when the weather turns mild with daily high temperatures in the 50s and 60s, you should reinstitute it. When temperatures are mild you should also keep an eye out for mites and insects and apply a miticide or insecticide if you detect these pests.
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