Authors
Ronald F.L. Mau, Extension Entomologist
Jayma L. Martin Kessing, Educational Specialist
Department of Entomology
Honolulu, Hawaii
Hosts
This scale is usually associated with yams (Dioscorea sp.), especially on yams in storage. However, it also occurs in other root crops such as ginger (Zingiber) and tumeric.
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Distribution
Distribution of this scale includes the Caribbean Islands, Ecuador, Fiji, Ghana, Hawaii, Honduras, Hong Kong, India, Ivory Coast, Malaya, Nigeria, Panama, Papua New Guinea, Philippines, Sierra Leone, Solomon Is., Tonga, Trinidad, Vanuatu and Zambia. The first record of this scale in Hawaii was in 1986 from tumeric growing on the Big Island. An eradication program ensued. Since then it has not been found. We believe it was probably erradicated from the State.
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Damage
The tumeric root scale feeds from the phloem of the host plant. Feeding damage due to an individual scale is small. However, when large populations are present, yellowing, defoliation, reduction in fruit set and loss in plant vigor result. Stored yams encrusted with tumeric root scales become dry and fibrous.
The tumeric root scale is classified as an armored scale. Unlike other scales, armored scales do not produce honeydew (Beardsley and Gonzalez, 1975). Armored scales feed on plant juices. Feeding sites are usually associated with discolorations, depressions and other host tissue distortions (Beardsley and Gonzalez, 1975).
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Biology
The tumeric root scale belongs to a family of scales called the armored scales. They are named this because they cover themselves with a shield or scale (puparium) composed of discarded skins (exuviae) and secreted matter. Scales belonging to the Aspidiella genus form a circular shaped shield that protects the body of the insect. This is contrary to other armored scales in which the shield is extended backwards from the scale.
Armored scales have 5 stages in their life cycle: egg, larva, second-stage larva, pupa and adult.
EGGS
The elongate eggs, with ends equally rounded, are laid within the puparium.
NYMPHS
The first stage larvae are active crawlers for a short time before selecting a feeding site. Once feeding begins the waxy protective shield starts to form.
The second stage larvae occur after the first molt in which the discarded skin becomes incorporated into the puparium. This stage is similar in appearance to the adult except it does not have the grouped circumgenital glands.
The last stage is sometimes referred to as pupae. They have lost all traces of mouth organs and are thus a non-feeding stage. They posses rudimentary legs, antennae, wings and stylus (mouth).
ADULTS
Adults are moderately convex, approximately 1/20 inch in diameter, and brownish-gray with a slight purplish tint. Females are generally circular in shape where males are more oval. Refer to Cockerell (1895) or Williams (1988) for a detailed microscopic description.
Females have rudimentary antennae and are unable to move about.
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Behavior
This scale is sedentary once it selects a feeding site.
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Management
NON-CHEMICAL CONTROL
No information available.
CHEMICAL CONTROL
No information available.
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References
Cockerell, T. D. A. 1895. IV. New Species of Coccidae. Psyche 7: 7.
Ferris, G. F. 1938. Atlas of the Scale Insects of North America, SII-188. Stanford University Press, California.
Heu, R. 1987. Notes and Exhibitions, Aspidiella hartii (Cockerell). pp. 22. Proc. Hawaiian Entomol. Soc.
Newstead, R. 1900. Monograph of the Coccidae of the British Isles. Volume 1. Adlard & Son, Bartholomew Close, Hanover Square, Dorking. 220 pages.
Williams, D .J. and G. W. Watson. 1988. Aspidiella hartii (Cockerell). pp. 44-46. In: The Scale Insects of the Tropical South Pacific Region, Part 1: The Armored Scales (Diaspididae). CAB International Institute of Entomology. The Cambrian News Ltd., Aberystwyth. 290 pages.
FEB/1992.
A-HARTII
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