|Crop Knowledge Master|
Coccus viridis (Green)
Ronald F. L. Mau, Extension Entomologist
Jayma L. Martin Kessing, Educational Specialist
Department of Entomology
Updated by: J.M. Diez April 2007
The green scale has a wide host range consisting of vegetable, fruit and ornamental crops. Plant hosts of economic importance include Annona (cherimoya, atemoya, sugar apple), anthurium, avocado, cacao, celery, coffee, flowering ginger, guava, lime, macadamia, orange, orchid and plumeria.
Thought to be of Brazilian origin the green scale is presently cosmopolitan in distribution throughout the Tropics except for Australia. This scale was first found on Oahu in 1905, and is now present on all islands at elevations below 3500 feet.
These scales are often found feeding along the main vein of the leaf and near the tips of green shoots. The green scale feeds from the phloem of the host plant. Damage due to the feeding of an individual scale is small. However, when 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. It is a serious pest of coffee in many countries, so devastating at times that coffee production ceased (LePelley, 1968).
Like other soft bodied insects such as aphids, leafhoppers and mealybugs, scales excrete honeydew. This sweet and watery excrement is fed on by bees, wasps, ants and other insects. The honeydew serves as a medium on which a sooty fungus grows, called sooty mold. Sooty mold blackens the leaf and decreases photosynthesis. On fruit, sooty mold reduces the marketability of the fruit (Elmer and Brawner, 1975).
The green scale, like other soft scales, feeds from the phloem of the host plant and may be found on stems, leaves and green twigs where they are associated with veins (Copland and Ibrahim, 1985). Damage due to the feeding of an individual scale is small. However, when large populations are present yellowing, defoliation, reduction in fruit set and loss in plant vigor are caused.
Scale insects belong to one of two types, the armored scales or the soft scales. The green scale is classified as a soft scale. These scales are protected by the chitinous body wall of the insect. Compared to the armored sales, they secrete very little wax. The body is usually smooth in outline, dome shaped, and brown, black or mottled in color. Soft scales retain their legs and antennae throughout adult life. Young females are primarily sedentary, but may move about for a brief time after feeding begins. Females are always wingless and males either have one pair of membranous wings or are wingless also. Reproduction is by eggs or the birthing of live young.
One generation of the green scale from egg to mature adult requires 1-2 months. Reproduction occurs exclusively without fertilization. Populations are composed solely of females, males have never been recorded.
Eggs are laid beneath the mature female where they are protected. They are whitish green and elongate-oval. The under surface of the leaf is preferred, and adult scales may be found in a line along both sides of the midrib and lateral leaf veins. Eggs hatch from a few minutes to several hours after being laid (Fredrick, 1943).
Nymphs, or immature green scales are oval, flat and yellowish green in color, and have six short legs. There are three nymphal stages before becoming an adult, each stage being larger and more convex than the previous stage.
Mature green scales are bright green with a brown or blackish, irregular, U-shaped, internal marking visible to the naked eye. The U-shaped marking is positioned lengthwise along the center of the scale. The presence of the marking distinguishes this scale pest from the green shield scale. These scales are somewhat oval in shape, quite flat and measure approximately 1/12 - 1/8 inch in length. The front end is more rounded and the rear has a distinct cleft extending about 1/4 of the way into the body. Dead scales are light brown or buff color and the black internal marking is absent.
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.
Scales are usually brought into greenhouse situations with the introduction of infested plant material. All plant material going into the greenhouse should be thoroughly inspected for scales and other insects before being introduced (Copland and Ibrahim, 1985).
The green scale is often associated with ants. Controlling ant populations help to reduce levels of this pest. 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.
Several parasites and predators to this scale are present in Hawaii. Parasites include, Microterys kotinskyi (Fullaway), Aneristus ceroplaste (Howard), Prococcophagus orientalis (Howard), Coccophagus hawaiiensis (Timberlake), Coccophagus ochraceus (Howard), Scutellista cyanea (Motschulsky), and Tomocera californica (Howard) (Zimmerman, 1948). Important lady beetle predators include: Orcus chalybeus (Boisduval), Chilocorus circumdatus (Schonherr), Azya orbigera (Mulsant), Cryptolaemus montrouzieri (Mulsant). These lady bug beetles have exerted substantial control (Clausen et al., 1978; Charanasri and Nishida, 1975).
Several insect-attacking fungi kill green scales in Florida, they include: Verticilium lecanii (Zimm.) (white-fringed fungus), Aschersonia cubensis (Cuban aschersonia), Nectria diploa (pink scale fungus) and a grayish blue fungus (Fredrick, 1943). In wet areas and the cooler, wetter winetr (at least in the Kona-area) of Hawaii, Verticilium is the predominant fungus on green scale and provides good control.
Chemicals used on scales are usually the same as those used on mealybugs. Depending on the host, excellent control can be obtained with malathion, carbaryl, volck oil or methomyl. Carbaryl is particularly effective, but its residues are harmful to beneficial predators and parasites. As in the use of all chemicals, consult the label or a database for crop registrations.
There are no listings for malathion, carbaryl, volck oil and methomyl as of April 2007.
Bess, H. A. 1958. The Green Scale, Coccus viridis (green) (Homoptera: Coccidae), and Ants. Proc. Hawaiian Entomol. Soc. 16(3): 349-355.
Charanasri, V. and T. Nishida. 1975. Relative Abundance of Three Coccinellid Predators of the Green Scale, Coccus viridis (Green) on Plumeria Trees. Proc. Hawaiian Entomol. Soc. 22(1): 27-32.
Clausen, C. P. (Ed.), B. R. Bartlett, E. C. Bay, P. DeBach, R. D. Goeden, E. F. Legner, J. A. McMurtry, E. R. Oatman, and D. Rosen. 1978. Green Scale, (Coccus viridis (Green)). pp. 73-74. In Introduced Parasites and Predators of Arthropod Pests and Weeds: A World View. Agriculture Handbook No. 480. US Department of Agriculture. Washington, DC.
Copland, M. J. W. and A. G. Ibrahim. 1985. Chapter 2.10 Biology of Glasshouse Scale Insects and Their Parasitoids. pp. 87-90. In: Biological Pest Control The Glasshouse Experience. Eds. Hussey, N. W. and N. Scopes. Cornell University Press; Ithaca, New York.
Dekle, G. W. 1976. Green Scale, Coccus viridis (Green). Fla. Dept. Agr. & Consumer Serv., Div. of Plant Industry. Entomology Circular No. 165.
Elmer, H. S. and O. L. Brawner. 1975. Control of Brown Soft Scale in Central Valley. Citrograph. 60(11): 402-403.
Fredrick, J. M. 1943. Some Preliminary Investigations of the Green Scale, Coccus viridis (Green), in South Florida. Florida Ent. 26(1): 12-15; 26(2): 25-29.
Hill, D. S. 1983. Coccus viridis (Green). pp. 225. In Agricultural Insect Pests of the Tropics and Their Control, 2nd Edition. Cambridge University Press. 746 pages.
LePelley, R. H. 1968. Coccus viridis (Green) - The Green Scale. pp. 353-355. In Pests of Coffee. Longmans, Green & Co., Ltd., London and Harlow. 590 pages.
Metcalf, R. L. 1962. Destructive and Useful Insects Their Habits and Control. McGraw-Hill Book Company; New York, San Francisco, Toronto, London. 1087 pages.
Nafus, D. 1990. Agricultural Pests of the Pacific Series, ADAP90-6. A publication of American Samoa Community College, Northern Marianas Community College, College of Micronesia, University of Guam and University of Hawaii.
Zimmerman, E. C. 1948. Coccus viridis (Green). pp. 311-318. In Insects of Hawaii. A Manual of the Insects of the Hawaiian Islands, including Enumeration of the Species and Notes on Their Origin, Distribution, Hosts, Parasites, etc. Volume 5. Homoptera: Sternorhyncha. 464 pages.
MAR/1992. Last update 7/3/06 MGW