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PACHYSANDRA DISEASES
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Q. I have a large hillside plot of pachysandra, roughly 40 x 15 feet. Last spring it had a fungus, due to the wet weather. I treated the disease with Daconil fungicide, and cut the pachysandra back with hedge clippers to allow better air circulation. |
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The pachysandra recovered, except for two sizeable patches, which are still have not filled in. Also, for the first time the entire plot - not just the bare spots - became infested with several types of common weeds, including crabgrass, dandelions, etc. I pulled them by hand last summer, but I am looking for a way to kill the weeds without harming the pachysandra. Can you recommend anything? Also, should I replant the bare spots or will they come back on their own? A: It sounds as though you took the proper steps to get the disease under control. Most likely the planting was suffering from volutella blight, the most common fungal disease that affects pachysandra. This disease starts as discrete tan or brown spots that eventually merge together and kill the entire leaf. You may notice concentric line patterns in the spots that resemble a bull’s-eye. Volutella will progress from the leaves down to the stems, and as happened in your bed, large patches of pachysandra can be killed. Management includes treatment with a fungicide such as Daconil (chlorothalonil) and thinning the planting to improve air circulation. It is also helpful to water during hot, dry weather to avoid drought stress. Watering is best done in the morning so that the foliage dries quickly. If you water in the evening, the foliage stays wet overnight, which creates a favorable environment for volutella to start again. The weed infestation that occurred during the summer probably was able to take hold because of the bare areas and because you thinned the patch out. Weeds have a much harder time becoming established in dense plantings, whether a ground cover bed or a lawn.
Herbicides work in a number of ways. They can be selective, which means they only affect certain weeds without harming the desirable crop. The herbicides used to control broadleaved weeds in lawns are selective. You can use a selective herbicide that kills grassy weeds such as crabgrass in ground cover beds, including Ortho Grass-B-Gon or Ornamec (fluazifop-P-butyl). They will not harm your pachysandra, but they will not control broadleaved weeds such as dandelions, either. Unfortunately, the herbicides that control broadleaved weeds will also kill pachysandra, so you probably still have to hand pull those weeds. Non-selective herbicides kill most plant material they contact and would not be suitable to use in a ground cover bed except possibly in the areas that are already bare of pachysandra. Round Up (glyphosate) and the many available glyphosate knock-offs currently available are examples of non-selective herbicides. Certain herbicides also work by preventing seed germination, or pre-emergently. These products do not kill standing weeds or those growing from roots or rhizomes. Once you have the bed free of weeds, you can apply a pre-emergent herbicide to keep weed seeds from germinating. Pendulum (pendimethalin) is labeled to control weeds growing from seed in pachysandra. Be sure to read and follow all label directions. For example, pendimethalin works best if watered in after application. If not, it begins to break down on exposure to sunlight, resulting in reduced control.
Since the bed
has not filled in since you got the disease under control, plan to
replant the bare spots this spring. Pachysandra is typically planted
on six-inch centers in staggered rows, the same way you lay bricks.
Avoid using pre-emergent herbicides in the newly planted areas until
the plants are well established. |
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