Leaf spots on pachysandra (Pachysandra) caused by volutella blight of pachysandra
Collapse of pachysandra (Pachysandra) caused by volutella blight of pachysandra
Blighted leaf on pachysandra (Pachysandra) caused by volutella blight of pachysandra
Leaf spot beginning on pachysandra (Pachysandra) caused by volutella blight of pachysandra
Leaf blight, Volutella pachysandrae, on Japanese pachysandra can be very detrimental to the plant. Two other leaf spots, Phyllosticta and Gloeosporium, cause leaf spots on foliage but are not as destructive as Volutella.
Ground covers, such as pachysandra, are sometimes used where grass or other plants will not grow due to low light. Consequently, the environmental stress factors, including prolonged leaf wetness or dry soils, can favor certain infectious diseases in the sites.
Symptoms and Diagnosis
Volutella blight begins as small, brown to tan spots on the leaves that enlarge to form blotches. These blotches can then spread and coalesce to form a blight where young growing tissue, especially leaves and twigs, are killed. Concentric line patterns form within the brown spots as leaves yellow and fall. Infected stems become brown to black in color and die.
Circular, spreading areas on diseased plants will be noticeable in the planting. The disease will be especially severe when plants are crowded and wet conditions prevail.
Many spore masses cause the spread of the disease, which is especially rapid among plants that have been weakened by the attack of scale insects or by winter injury. The sexual stage of this fungus is Pseudonectria pachysandricola. Under moist conditions, salmon- to pink-colored masses of fungal spores form on the surface of dead stems in spring. Initial infections may lead to large patches of plants killed.
Integrated Pest Management Strategies
1. Maintain plant vigor. Purchase healthy plants and maintain this condition by watering during drought. Water early in the day so that drying occurs before evening. Avoid splashing of water. Fertilize as needed or as indicated by soil testing.
2. Select planting area carefully. Plants should be planted in a well-draining soil. If the site is persistently wet, amend the soil or raise the bed before planting.
3. Removal. Lift out and destroy severely diseased plants. Bury or remove from the site. Do not place in the compost pile.
4. Use fungicides. It is difficult to thoroughly apply fungicides unless using a forceful sprayer. Fungicides can be applied beginning in spring and at 7 to 14 day intervals through early summer. Once temperatures rise above 90 degrees F, discontinue application. Pesticides registered for use include chlorothalonil (Daconil), copper, mancozeb, maneb, and thiophanate methyl (Cleary 3336).
5. Mulch. Mulch with leaf mold in the spring to cover up fallen debris containing inoculum.
6. Thinning. Thin plants in fall, during dry weather, to remove dense growth.
7. Pests. Scale is a harmful pest on pachysandra and may make it more susceptible to disease. The female insects are dark brown and shaped like oyster shells. The males are smaller and narrower, pure white, and are very prominent on the leaves and stems. Heavy infestations of scale can be brought under control by applying summer oil spray before the new growth starts in spring. Follow this with several applications of a scale insecticide like malathion or Sevin at 2-week intervals or several applications of a scale insecticide or summer oil every 10 days to 2 weeks starting in mid-May.
Strategies 2, 3, 5, and 6 are strictly organic approaches. Using an appropriate organic fertilizer would be a viable organic approach to Strategy 1. Of the fungicides listed in Strategy 4, consult the Organic Materials Review Institute (OMRI™) for appropriate organic copper products.