This disease, caused by a bacterium (Xanthomonas campestris pv. hederae), occurs frequently on English ivy growing in humid areas. Leaves kept constantly moist are particularly susceptible to invasion by these bacteria. The bacteria spread from plant to plant in splashing rain, on insects such as ants, bees, and flies, and on contaminated equipment. People also spread the bacteria when they work around wet, infected plants. Other organisms often enter the dying tissue and stem lesions, causing further decay.
When the foliage is dry, remove and destroy infected leaves and plants. Avoid planting English ivy in hot, humid areas. Water early in the day to allow the foliage to dry quickly.
Several different fungi cause leaf spotting on ivy. Some of these fungi may kill tender stems. Others merely spot the leaves and are unsightly. The fungi are spread from plant to plant by wind, splashing water, insects, and contaminated tools. They spend the winter on diseased plant debris left in the garden. Leaf spot affects a wide variety of plants, including flowers, vegetables, and groundcovers. Most leaf spot fungi do their greatest damage in temperatures between 50° and 85°F.
Spray infected plants with a fungicide labeled for fungal leaf spot, following label directions. Remove and throw away leaves that are spotted on more than half their surface to reduce the spread of infection. Don''t work in the diseased plants when the leaves are wet, or you will help spread the fungi. Water early in the day to allow the leaves to dry before nightfall.
Several species of this common insect feed on ivy. Mealybugs damage plants by sucking sap, causing leaf distortion and death. The adult female mealybug may produce live young or may lay eggs in a white, fluffy mass of wax. The immature mealybugs, called nymphs, crawl all over the plant and onto nearby plants. Soon after they begin to feed, they produce white, waxy filaments that cover their bodies, giving them a cottony appearance. As they mature, they become less mobile. Mealybugs cannot digest all the sugar in the sap, and they excrete the excess in a fluid called honeydew, which coats the leaves and may drop onto surfaces below the plant.
Separate infested plants from those not affected. If only a few mealybugs are present, wipe them off with a damp cloth or cotton swabs dipped in rubbing alcohol. Apply an insecticidal soap labeled for this pest.
Several different types of scale insects attack ivy. Some types can infest many different plants. Scales hatch from eggs. The young, called crawlers, are small (about 1/10 inch) and soft bodied and move about on the plant and onto other plants. After moving about for a short time, they insert their mouthparts into the plant, feeding on the sap. The legs atrophy, and the scales remain in the same place for the rest of their lives. Some species of scales are unable to digest fully all the sugar in the plant sap, and they excrete the excess in a fluid called honeydew, which may cover the leaves or drop onto surfaces below.
Isolate infested plants as soon as scales are discovered. Remove as many scales as possible with a cloth or toothbrush dipped in soapy water. Spray plants with an insecticidal soap or a horticultural oil labeled for use indoors.
This common black mold is one of several species of fungi. These fungi grow on the sugary material left on plants by aphids, mealybugs, scales, whiteflies, and other insects that suck sap from the plant. The insects are unable to digest all the sugar in the sap, and they excrete the excess in a fluid called honeydew, which coats the leaves. The honeydew may also drip from infested overhanging trees and shrubs onto ivy growing beneath them. Sooty mold is unsightly but is fairly harmless because it does not infect the leaf tissue. Extremely heavy infestations prevent light from reaching the leaf and may cause the leaf to turn yellow. The presence of sooty mold indicates that the ivy or another plant above it is infested with insects.
Rain will eventually wash off sooty mold. Plants can also be rinsed off with a solution of soapy water, using a mild soap. If only a few leaves are infested, just wipe off the mold with a wet rag. Prevent more sooty mold from growing by controlling the insect that is producing the honeydew. Inspect the leaves and stems of the ivy and plants growing in the area to determine what type of insect is present.
These mites, related to spiders, are major pests of ivy. They cause damage by sucking sap from the undersides of leaves. As a result of their feeding, chlorophyll disappears, producing the stippled appearance. Spider mite webbing traps cast-off skins and debris, making the plant messy. Under warm, dry conditions, mites can build up to tremendous numbers.
Isolate infested plants from others. Take plants outside or into a shower and wash the mites off the leaves with a strong spray of water. Keep air around the ivy humid to help prevent infestation and proliferation.