Leaves Discolored, Webbed Over - Spider Mites
Spider mites are about 1/50 inch long, barely visible to the unaided eye. They're not true insects, but are related to spiders, with four pairs of legs, piercing-sucking mouth parts, and very compact bodies. They may be yellow, green, red or brown. Upper leaf surfaces of violets stippled with small yellow dots or red spots suggests the presence of mites. Leaves, their stems, and adjacent branches may be distorted or covered with fine webs. Start control measures as soon as you notice the first stippling of the leaves. Dig up and trash seriously infested violet clumps, and spray remaining pests with insecticidal soap every 3 to 5 days for 2 weeks.
For more information see file on Dealing with Mites.
Leaves Curled and Distorted - Aphids
Aphids, also called "plant lice," are soft-bodied, pear-shaped sucking insects about the size of the head of a pin. They sometimes cluster on leaves and tender buds of violets. Their feeding retards plant growth. Violet leaves may turn yellow or brown. They wilt under bright sunlight, or sometimes curl and pucker. Spray the insects with insecticidal soap every 3 to 5 days. If that doesn't work, spray them with pyrethrum every 5 to 7 days.
For more information see file on Dealing with Aphids.
Holes In Leaves - Violet Sawflies
Sawfly adults are small black and yellow wasplike insects with 4 wings. The larvae are 1/2 inch long, dark olive-green with white spots, and resemble caterpillars. These larvae feed on violet leaves at night. They chew holes in lower leaves and may defoliate entire plants. Spray the pests with methoxychlor or malathion.
Leaves Webbed Together; Foliage Discolored - Leaftiers
Adult leaftier moths are brown or gray, 1/4 to 1/2 inch long, with a 3/4 inch wingspan. Their larvae are caterpillars, 3/8 to 3/4 inch long, dark to light green or cream to yellow, with a white stripe running down the back. The larvae protect themselves while feeding by webbing leaves together with strands of silk. This foliage becomes ragged and unsightly, turns brown and dies. Spray vulnerable plants with BT (Bacillus thuringiensis) just as the caterpillars begin feeding. They will ingest the BT and die in a matter of days. Or, if necessary, spray them with a pyrethroid insecticide. If there are not too many, simply crush the larvae in their webbed hideouts.
Plants Stunted, Yellowed; Root Lesions - Nematodes
Nematodes are not insects, but slender, unsegmented roundworms. Most are microscopic-sized soil dwellers. They have piercing-sucking mouthparts and feed on cell contents. Several kinds of nematodes occasionally attack violet leaves or roots. Infested plants look sickly, wilted or stunted, with yellowed or bronzed leaves. They decline slowly and die. The roots are poorly developed, have little knots in them, and may be partially decayed. Dig up severely damaged plants, and add lots of compost (especially leaf mold), if it is available, to the soil to encourage beneficial fungi that attack nematodes. If the pests are a recurrent problem, consider planting violets in another location.
For more information see file on Dealing with Nematodes.
Ragged Holes In Leaves - Slugs
Slugs are essentially snails without protective shells. They are usually 1 to 2 inches long (some species grow up to 8 inches). They're white, gray, yellow, or brownish black. Slugs and snails are attracted to moist, well-mulched gardens and acidic soil. They are likely to be lurking in woodsy, natural areas where violets grow. Active at night, they rasp holes with their file-like tongues in leaf and stem surfaces. They hide under boards or leaf litter during the day. Trap them with a shallow plate baited with beer set on the soil near the violets. The slugs are attracted to the yeast in the beer, climb in, and drown. Begin trapping the pests 3 to 4 weeks after the last frost.
For more information see file on Dealing with Slugs and Snails.
Blotched Leaves; Spotted Petals - Anthracnose
Anthracnose, a fungal disease, may attack violets, producing a browning or blotching of the leaves. The dead areas are marked by distinct black margins. Petals of infected flowers are spotted and develop abnormally. The plants may be killed by serious infection. Dig up and destroy infected plants. Spray other plants with zineb or maneb fungicides. Disinfect any garden tools used on the infected plants with household bleach or rubbing alcohol to avoid spreading this fungus.
For more information see file on Dealing with Fungal Disease.
Leaves Spotted Or Blotched - Fungal Leaf Spot
Many kinds of leaf spots are caused by fungi that thrive on moist violet leaf surfaces and cause transparent to brown or black spots that disfigure the leaves. Some fungal spots are surrounded by flecks or black dots, their spore-bearing fruiting bodies. Often spots come together to form larger patches of dead tissue. Pick off and discard infected leaves. Remove dead plant debris promptly from the garden to reduce over wintering spore populations. Dig out and discard seriously infected plants together with their soil. Mulching helps prevent splash-borne infection in outdoor plantings. Spray at weekly to 10 day intervals with wettable sulfur, maneb or zineb, particularly in wet weather.
For more information see file on Dealing with Fungal Disease.
Powdery Spots On Leaves - Rust
Rust diseases caused by various fungi produce pale yellow areas on violet upper leaf surfaces and powdery orange spots of fruiting bodies on their undersides directly beneath. Infected stems and flowers may be seriously deformed. Remove any infected leaves as soon as possible. Remove and destroy all garden debris before plants start to grow in the spring. Control weeds in and around the garden. Control insect pests with pyrethrum or rotenone. Prevent rusts with periodic sprays of wettable sulfur, starting several weeks before the disease normally appears. Space plants widely apart for good ventilation, and avoid wetting the foliage when watering.
For more information see file on Dealing with Fungal Disease.
Leaves Covered With White Powder - Powdery Mildew
Powdery mildews are caused by fungi that live on the surface cells of the plant, not inside them. Infected leaves are covered with a white or ash-gray powdery mold. Badly infected violet leaves become discolored and distorted, then drop off. Powdery mildews thrive in both very humid or very dry weather. Spray affected plants thoroughly with wettable sulfur once or twice at weekly intervals starting as soon as the whitish coating of the fungus appears. Allow ample spacing between plants and collect and discard all above ground refuse in the fall.
Crowns and Roots Rot; Odor Present - Crown Rot
Crown and root rot, caused by soil-dwelling bacteria and fungi, attack a few spots on the crown where the root system grows from the base of the plant stem at first. It then spreads to the entire crown, turning it into soft, smelly mush which may then be invaded by fungi. If the plant is already in leaf, the lower leaves are discolored and the young shoots begin to wilt. The roots are blackened, rotten and covered with white fungal threads. The whole plant dies in a few days. Remove and discard in the trash the infected plants and the soil near their roots. Thoroughly cultivating around plants allows the soil to dry out and hinders the spread of the fungus. If you catch the disease early, spray the crowns with ferbam or captan fungicides. The disease is most likely to occur in the late winter thaw when dead leaves decompose on ground and harbor bacteria and fungi that spread to healthy tissue. Keep winter mulch away from the crowns to reduce problems.
For more information see file on Dealing with Fungal Disease.
