The Home & Garden Education Center has received an abundance of inquiries related to Japanese pachysandra, (Pachysandra terminalis) during the last few weeks. Homeowners all over Connecticut are experiencing difficulty with this groundcover. It first becomes noticeable as other things around it start to green up in the spring and we see that the leaves are remaining a sickly shade of yellowish-green.
As it catches our attention we notice that the plantings in general look a bit sad and sparse. A closer look at the leaves will reveal that there are areas of irregular brown blotches that have concentric line patterns within the affected area and pretty sharply defined darker brown edges. The center of the spots will can appear much lighter if the salmon-pink fungal spores are present.
The browning areas will continue to spread and darken and can encompass the entire leaf as it dies. The cankers that can develop on the stems and stolons can girdle the stem and cause the plant to wither and die by disrupting the transport of water and minerals through the plants vascular system.Unfortunately this can happen in as little as two weeks, especially if the weather is wet and humid. It has certainly been wet over the last week and although the total precipitation is around the average 1” needed for growing plants it has come in a slow but steady sprinkle allowing plants little time to dry out between the showers.
This is all the work of the fungus called Volutella pachysandricola, or Volutella Leaf and Stem Blight. This fungus is considered an opportunistic pathogen that attacks weak plants. It can infect leaves, stems, and stolons and is considered the most destructive disease of pachysandra. The pink spores that appear in the spring will darken to reddish-orange in the late summer and fall when a second type of spore is produced.
This winter may have provided the perfect storm needed by Volutella to thrive. Drying winds and winter sun can desiccate pachysandra if there is not an adequate cover of snow to provide protection. Also, many beds of pachysandra are near roads and sidewalks where salts may dry them out further. A cover of mulch could provide just enough needed winter protection for plantings in these areas but it should be removed in the early spring. Some symptoms of winter injury or sunscald such as tan or scorched leaves may initially appear to be Volutella but they will not exhibit the characteristic concentric lines of the disease.
Those same pachysandra beds that are near sidewalks or roads or are used as edgings can receive damage from mowers, clippers and weed whackers (Or as they are called in Australia, ‘whipper snippers’. I just love that!). Cuts from lawn equipment can provide an opening in plant tissue and when the plant is wet the fungal spores are able to infect it easily and travel to the stems where they will cause the girdling mentioned earlier.
Good sanitation practices can be helpful when dealing with pachysandra blight. It is too late for a good fall cleanup now but you can still remove any plant debris that remains. During dry weather remove and bag (not compost) any diseased plants to reduce the inoculum. Thinning out beds will also help improve the air circulation that can speed up drying. Fungicides can be used as preventives for new growth or when wounds occur and systemic curatives can be used when symptoms first appear although they will not correct damaged tissues. Allegheny pachysandra (Pachysandra procumbens) can be less susceptible to the disease or you could consider another groundcover such as creeping myrtle or vinca.
Another source of wounds to pachysandra that should not be overlooked in insect damage. Scale insects such as Euonymous scale, two-spotted spider mites, and root knot nematodes have been found on plant samples that have come in to the Center. Horticultural oils and insecticidal soaps applied now can help control scale, just be sure to thoroughly coat the pests with the product. A miticide can be used on the spider mites but there is currently no control chemical treatment for the nematodes.
If you are experiencing these symptoms in your pachysandra beds you can get additional information from the Connecticut Agricultural Experiment Station fact sheet entitled Volutella Blight of Pachysandra, on our website at Pachysandra Leaf and Stem Blight, or by contacting us at the UConn Home & Garden Education Center.