During the spring, many homeowners notice changes or problems arising in their gardens and landscapes. Throughout May, the Plant Diagnostic Lab received many samples and emails of evergreen plants such as junipers, arborvitae, cedars, and boxwoods for diagnosis. Phomopsis Tip Blight on conifers and Volutella Blight on boxwood are two common diseases seen this time of year. Homeowners tend to notice symptoms in the spring and early summer when conditions are wet and damp and conducive for disease development.

Phomopsis blight is caused by the fungal pathogen Phomopsis juniperovora. Plants that are commonly affected include juniper, cedar, cypress, and arborvitae. Most infections occur in April through early June and in the fall but can occur throughout the growing season on young foliage during wet and humid conditions. Symptoms first appear on immature tissues about 3-5 days after infection. Older, mature branches are resistant. After infection, small yellow spots can be seen on the foliage. Eventually, shoot tips will turn a reddish, brown color after the fungus has entered the xylem.

B1 phomopsis juniper Bruce Watt bugwood.org

Infected branch tips on juniper. Bruce Watt UMaine. bugwood.org.

Over time, cankers will form at the base of the blighted shoots, appearing as a gray band. These cankers can girdle stems less than 1 cm in diameter. Black pycnidia, or tiny fruiting structures, form on killed tissue 3-4 weeks after infection. During wet weather, yellowish conidia, or spores, are extruded from the pycnidia and spread by wind and rain splash. The pathogen can remain on the host and continue to spread spores for up to 2 years when environmental conditions are favorable.

Volutella blight on boxwood hosts is caused by the fungal pathogen Pseudonectria buxi. Symptoms begin in spring as poor vigor and leaves turning light green to straw or tan colored. Leaves turn upwards and tend to remain attached to the branch. This key observation can help distinguish Volutella from boxwood blight, which causes rapid defoliation. Additionally, distinctive black stem streaking and cankers are signs of boxwood blight. Volutella can cause sunken lesions on the stems and plants may eventually lose bark.

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Volutella blight symptoms. Photo by Lillian Borbas, UConn 2021

B3 Straw colored leaves stem lesions L. Borbas

Straw-colored leaves attached to branches. Sunken stem lesions. Photo by Lilian Borbas, UConn 2021

B4 Black stem streaking Mary Ann Hansen bugwood.org

Black stem streaking on a boxwood diagnosed with Boxwood Blight. Mary Ann Hansen. VPI & State University. Bugwood.org

On the undersides of leaves, Volutella will form distinctive orange to salmon-colored sporodochia (fruiting bodies) in moist and humid conditions. The pathogen is spread through rain splash or contaminated tools and is commonly associated with plants that are stressed. Maintaining plant vigor and utilizing the cultural controls outlined below can help manage this disease.

B5 Sporodochia boxwood Bruce Watt bugwood.org

Sporodochia on boxwood leaf. Bruce Watt, UMaine. Bugwood.org.

Management recommendations

For both Volutella and Phomopsis blight, control options are similar. When growing plants susceptible to these diseases, preventative methods, proper planting practices, and cultural controls are important for management. Proper site selection can discourage infection, for example, well drained sites with proper light exposure and air circulation. Ensuring that plants are properly spaced will reduce humidity and moisture around the foliage. Make sure the plant’s mature size is considered when planting. Properly irrigate and fertilize based on the needs of the plant and planting site. Do not water with sprinklers or overhead irrigation as this will encourage prolonged leaf wetness. Avoid letting weeds or other vegetation grow close to the plants. Excessive watering or fertilizing can make the plants more susceptible to infection. Avoid shearing, wounding, or pruning plants in wet, humid weather as this will aid in disease spread.

Regularly check your plants for signs of the symptoms described. If these symptoms are observed, cultural practices should be implemented first. Remove all infected tissue during dry weather, cutting 3-4 inches back from the damage. Disinfect tools between plants and cuts with 10% bleach or 70% isopropyl alcohol. Discard or burn the infected branches as they can be a source of disease. If the plant is heavily infected, it may need to be removed. Consider choosing plants that are more resistant or not susceptible to the disease.

Fungicides may need to be applied if infections become severe and these cultural controls are exhausted. However, many fungicides are used preventatively and should only be used after cultural controls have been tried. They are often only effective if followed by this management and applied before new growth begins in the spring. Whenever using fungicides, always read and follow the label for information on proper rates and application times.

Lillian Borbas

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.

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Affected bed of pachysandra

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.

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Pachysandra leaves showing signs of Volutella blight

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.

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Close-ups of the Volutella damage and spores

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.

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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.

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Vinca major, also known as variegated greater periwinkle

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.

Euonymous scale

Euonymous scale image by Joan Allen

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.

-Susan Pelton