Plant Health Problems
Diseases caused by Fungi:
Volutella blight, Volutella pachysandrae.
Volutella blight is the most destructive disease of pachysandra in the Northeast. Both leaves and stems are attacked by this fungus. Leaves develop irregular tan to brown blotches, often with concentric lighter and darker zones with dark brown margins. These blotches gradually increase in size until the entire leaf turns brown or black and dies. Stem cankers appear as a browning of the stem at the terminal, mid-stem, or at ground level. As these cankers girdle the stem, they cause the whole plant to wither and die. Plants often die in patches and the disease commonly produces circular patterns in the bed. Volutella blight is more severe in plantings weakened by winter injury, insect infestation, recent transplanting or shearing, drought, and exposure to full sun.
To manage this disease, all plant debris and severely diseased plants should be removed and destroyed. Since Volutella blight is associated with plant stress, attempts should be made to control insect infestations and to maintain good growth and vigor by watering during periods of drought and by fertilizing in the spring. The planting should be thinned periodically to prevent dense growth and increase light and air circulation. Fungicides can also supplement other control strategies. Among the compounds registered for use in Connecticut are thiophanate-methyl, chlorothalonil, and mancozeb. Consult the label for dosage rates and safety precautions. Plants can be sprayed when new growth starts in the spring and again 2-3 more times according to label directions to protect newly emerging tissues. Additional applications may be necessary during wet weather. For more information, see the fact sheet on Volutella Blight of Pachysandra.
Diseases caused by Physiological/Environmental Factors:
Symptoms of scorch often appear in late winter and early spring as papery, tan margins or patches on the leaves. Scorch can be associated with many factors including extremely cold winter temperatures, drying winds, lack of snow cover, and extreme temperature fluctuations and freeze/thaw cycles.
Control measures are usually not necessary for this problem since plants recover once new growth resumes in the spring.
Euonymus scale, Unaspis euonymi.
Pachysandra is often severely infested by this scale. The female scales are gray and pear-shaped, while the males are smaller, narrower, and whiter. There are probably two generations each season, and the winter is passed in a nearly mature condition; eggs are formed during May and hatch later in the month. Badly infested plantings may be renovated by mowing and removing clippings, allowing plants to regrow from stolons. Among the compounds registered for control of this pest in Connecticut are horticultural oil, insecticidal soap and malathion. Spraying with ultrafine horticultural oil, either in mid-April for a dormant treatment or early June and again in mid-July, will control this scale while conserving the natural predators and parasites that might be present. Sprays of insecticidal soap and malathion applied in early June and again in mid-July will also control this scale. Consult the label for dosage rates and safety precautions.
San Jose scale, Quadraspidiotus perniciosus.
Occasionally, this scale infests pachysandra. Large infestations of the San Jose scale can destroy an entire planting. Partially-grown scales overwinter under their circular gray covering or scale on the twigs. In late may the males emerge from under their scales to mate with the immobile females. Females are circular and cone-shaped, and their circular scales are about 1/16" in diameter, with a raised center or nipple. The males are smaller and elongate, with the nipple not centered on the scale. Females give live birth to tiny bright yellow crawlers in June. The young crawlers quickly settle, insert their long mouthparts into the twigs, and then suck sap from stems. As they grow, the crawlers secrete a waxy filament that becomes their scale or covering. Overlapping generations are present from June through September. Scales may be controlled by applying horticultural oil at a dormant timing or in June when crawlers are active. Diazinon, which is among the compounds registered for control of this pest in Connecticut, can also be applied against the crawlers in June. Consult the labels for dosage rates and safety precautions. To detect the yellow crawlers, wrap black tape coated with Vaseline around stems. Adult flights may be detected with pheromone traps. An alternative control practice would be renovation of ground cover plantings, described under Euonymus scale.
Oystershell scale, Lepidosaphes ulmi.
For the biology of this scale, see Apple. A dormant application of horticultural oil will control overwintering scales. Summer application of ultrafine oil can also be helpful. Spraying with malathion, ultrafine oil, or insecticidal soap, which are among the compounds registered for control of this pest in Connecticut, about June 15 kills the young crawlers. Consult the label for dosage rates and safety precautions. An alternative control practice would be renovation of ground cover plantings, described under Euonymus scale.