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Yellow spotting of the leaves on hollies is a symptom of scale infestation./ IN addition, you might find sooty mold growing on leaves where honeydew was secreted by the scale. Shrubs eventually lose their vigor. If you notice these symptoms, look for the pests themselves. Holly scale (Dynaspidiotus britannicus) usually gather on leaf undersides, but will also infest twigs and berries. They resemble small bumps, having a rounded covering which protects them as they feed. The covering is oval, light brown, to tan in color, and extremely small. The insect itself and its eggs are lemon yellow. These scale overwinter in a partially grown condition. They begin to feed in late March or early April and lay eggs in June and july. Only 1 generation occurs a year. Although holly scale is most common, 11 other species of scale insects attack hollies. These include black, California red, greedy, holly, lecanium, oleander, peach, pit-making, soft, and tea scale.
If you catch these pests before too many of them have gathered on your shrubs, simply scrape them off plant surfaces with a cotton swab dipped in rubbing alcohol. Spray heavily infested plants with a mixture of alcohol and insecticidal soap every 3 days for 2 weeks. Make this mixture by combining 1 cup isopropyl alcohol and 1 tablespoon commercial insecticidal soap concentrate with 1 quart water. If you are using insecticidal soap already mixed with water, add 1 tablespoon alcohol to a pint of the diluted soap. If scale insects have consistently been a problem, try spraying hollies in late winter or early spring with a 3% dorman oil to smother overwintering scale and keep them from getting a good start.
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