Pale Leaves Signal an Environmental Problem
Stress from various environmental problems such as too much sun, wet soil, or iron deficiency causes pachysandra leaves to lose their rich green color. Too much sun bleaches pachysandra foliage to a pale, washed-out appearance. Leaves will be light green to yellow, and growth is generally poor. The only solution is to move it into shade, and replace it with a groundcover adapted to sun, such as cotoneaster or creeping euonymus.
If your plants are already growing in shade, check their soil for a drainage problem. Plant roots may be sitting in wet soil, which will eventually kill them. Provide a ditch or other method to drain the water away, or try raising the soil level of the area and replanting.
If the pale, yellowed leaves retain green color along the veins their soil is not acid enough. Plants cannot access the iron in it and develop a condition called iron chlorosis. If a pH meter indicates that the soil needs to be more acid, sprinkle powdered sulfur or used coffee grounds on it or use a product containing iron sulfate or “chelated” iron according to package directions.
Small Bumps on Leaves and Stems Means Scale
The first sign of a scale attack is yellowing of the leaves, followed by leaf drop, reduced growth, and stunting. Heavy infestations kill plants. Some species of scale excrete honeydew, which attracts ants and encourages the growth of sooty molds. If you notice any of these symptoms, look for bumps--rounded waxy shells--which shelter the scale insects as they suck plant sap from stems and leaves. They may be colored white, yellow, or brown to black, and are about 1/10 to 2/5 inch in diameter.
If your pachysandra planting is too extensive to scrape the pests off infested plants with your fingernail, spray the affected foliage with light horticultural oil to smother them in their shells.
For more information see file on Dealing with Scale.
Leaves Bound with Silk Strands Indicates Leaftiers
Leaftiers are the larvae of small moths. They are 3/4-inch-long olive green caterpillars with two prominent black spots near their heads. They protect themselves while feeding by rolling leaves into tubes and binding them with strands of silk. As they feed, the foliage becomes ragged, turns brown and dies.
If there are not too many caterpillars, handpick the larvae in their leafy tubes, crush and discard them. Control larger infestations in late spring by spraying affected foliage with Bacillus thuringiensis (Bt) as soon as you see eggs or the larvae before they take refuge inside their little leaf tubes. The hatching caterpillars will eat the bacterium, stop eating and die in a day or two. Mix the Bt according to package directions just before you're ready to use it. Because Bt is biodegradable and rapidly inactivated by sunlight and rain, spray every 3 to 5 days until the pests disappear.
For more information see file on Dealing with Caterpillars.
Leaves Stippled Yellow or Red Means Spider Mites
Spider mites are tiny spider-like pests about the size of a grain of black pepper. They may be red, black, brown, or yellowish-white. They feed by sucking plant juices, removing chlorophyll and causing small white dots to appear on the foliage. The toxins they simultaneously inject into leaves discolor and distort them. Foliage of mite-infested plants becomes stippled, yellow, and dry, and sometime fine webbing is visible.
Pachysandra under stress from strong sun or drought is vulnerable to mites. To control mite infestations, spray plants with a forceful spray of water every other day for 3 days, to knock the mites from the leaves. If they are still present, spray them with a product containing insecticidal soap as directed on its label.
For more information see file on Dealing with Mites
Yellowed Leaves, Reduced Plant Vigor Means Root Knot Nematodes
Nematodes are whitish, translucent, wormlike creatures barely visible to the naked eye, about 1/50 to 1/10 inch long. Pachysandra plants whose roots are infected by them look sickly, wilted, or stunted. They develop yellowed or bronzed foliage, and then they decline slowly and die. Upon inspection roots are poorly developed, show knots or galls, and may be partially decayed. Nematode activity is most obvious in hot weather, when plants recover poorly from the heat. Northern root knot nematodes attack pachysandra.
Control these pests by adding lots of compost (especially leaf mold) to the soil around the plants to encourage beneficial fungi that attack nematodes. Add liquid fish emulsion to the soil as a drench. It is toxic or repellent to nematodes.
Shriveled Leaves, Dark Spots on Stems Caused by Stem Canker
A fungus (Volutella pachysandrae) that attacks only pachysandra causes brown to black blotches to appear on its leaves, eventually killing them. Similar dark spots (cankers) develop on the stems. Masses of pink spores sometimes appear on the stem cankers. This disease may attack plants that are injured or overcrowded.
Remove and destroy infected leaves and stems as soon as you notice them, cutting the pachysandra back to several inches below the infected area. Improve air circulation by thin overcrowded plants. Disinfect pruning tools in a solution of household bleach and water after using them to avoid spreading this disease. Because the fungus does not live in the soil you can replant with more pachysandra if desired.
For more information see file on Dealing with Fungal Disease
Foliage Browned and Burned By Dog Urine.
Dog urine is mildly toxic to most ornamental plants. It may discolor pachysandra foliage and even kill branches. Spray the vulnerable foliage at corners and edges of beds with an anti-transpirant spray product to provide some protection. Also try screening the plants at the edge of the groundcover patch with low fencing or spraying foliage with an aerosol repellent spray. Prune out damaged areas.