Green Scale and Sooty Mold
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The green scale, Coccus viridis, an insect pest of coffee, citrus and other plants, is found out-of-doors and in greenhouses in Florida. This pest was first found in Hawaii in 1905.
Eggs hatch into crawlers that wander around the plant or disperse to other hosts. Once a suitable leaf or green shoot is found the nymphs settle and begin to feed. They usually remain in this same spot unless their position becomes unfavorable. The mature female does not move. Succulent leaves and stems are preferred, and adult scales may be found in a line along both sides of the midrib and lateral leaf veins. |
Often they attack the young shoots, then one can usually see only a mass of scales.
The green scale is often associated with several types of ants including big-headed and long-legged ants, which help to protect and move scales. Ants protect the green scales from lady beetles and other predators. In turn, the ants feed on the sweet honeydew excreted by the scales. Without the ants the green scale is more vulnerable to predation by beetles. Controlling ant populations can help to reduce levels of this pest, but it can be difficult to find products for coffee that control ants quickly. Hence, the control of scales and other sucking insects is recommended instead, to discourage ants to trees. Usually green scale infestations are accompanied by sooty mold, a black fungus growth, which develops on honeydew excreted by the scale. Accumulations of sooty mold cause the infested plant to not only be unsightly, but it reduces the plant's ability to photosynthesize, resulting in sickly trees.
When scale large populations are present, yellowing, defoliation, reduction in fruit set and loss in plant vigor are caused. This pest is especially damaging to young trees in the first two years after transplanting. Green scale management is facilitated by an entomopathogenic fungi called White Halo Fungus (Verticillium lecanii), which may cause high levels of mortality at cooler times of year, particularly in coffee-growing areas. Parasitoids and predators have also been shown to play a role in green scale suppression. Insecticides labeled for use on coffee may be used to control scale populations as well as ants. Learn more about green scale and its control (pages 15, 27-29) in the Hawaii Coffee Pest Management Strategic Plan.
The green scale is often associated with several types of ants including big-headed and long-legged ants, which help to protect and move scales. Ants protect the green scales from lady beetles and other predators. In turn, the ants feed on the sweet honeydew excreted by the scales. Without the ants the green scale is more vulnerable to predation by beetles. Controlling ant populations can help to reduce levels of this pest, but it can be difficult to find products for coffee that control ants quickly. Hence, the control of scales and other sucking insects is recommended instead, to discourage ants to trees. Usually green scale infestations are accompanied by sooty mold, a black fungus growth, which develops on honeydew excreted by the scale. Accumulations of sooty mold cause the infested plant to not only be unsightly, but it reduces the plant's ability to photosynthesize, resulting in sickly trees.
When scale large populations are present, yellowing, defoliation, reduction in fruit set and loss in plant vigor are caused. This pest is especially damaging to young trees in the first two years after transplanting. Green scale management is facilitated by an entomopathogenic fungi called White Halo Fungus (Verticillium lecanii), which may cause high levels of mortality at cooler times of year, particularly in coffee-growing areas. Parasitoids and predators have also been shown to play a role in green scale suppression. Insecticides labeled for use on coffee may be used to control scale populations as well as ants. Learn more about green scale and its control (pages 15, 27-29) in the Hawaii Coffee Pest Management Strategic Plan.
Collecting Plant Disease and Insect Pest Samples for Problem Diagnosis
Learn how to best collect and submit disease, insect, mite and nematode samples to the UH Agricultural Diagnostic Service Center (ADSC) for diagnosis. Click here for ADSC analytical service fees.
Learn how to best collect and submit disease, insect, mite and nematode samples to the UH Agricultural Diagnostic Service Center (ADSC) for diagnosis. Click here for ADSC analytical service fees.
Coffee Leaf and Soil Sampling
Learn how to correctly sample and submit coffee leaf and soil samples for proper analysis of plant nutritional status and soil pH and nutrient status.
Learn how to correctly sample and submit coffee leaf and soil samples for proper analysis of plant nutritional status and soil pH and nutrient status.
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