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Unaspis yanonensis

Basic information
Scientific name Unaspis yanonensis

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Common names Arrowhead snow scale, Japanese citrus scale, Oriental citrus scale
Higher taxon Diaspididae, Coccoidea, Hemiptera
Natural range Middle to southern continental China.
Habitat Parasite on citrus
Invasion information
Range in Japan Central to western part of Honshu, Shikoku, Kyushu, and Amami Islands (Amamioshima and Tokunoshima Is.). This species was temporarily established but eradicated immediately on Okinawajima Is. Range in Japan
Origin Unknown.
Date The first record in Japan was in 1907 at Nagasaki Pref.
Route Unknown.
Impact Damage on citrus agricultures.
Native organism(s) affected: Various citrus.
Regulation in Japan Diaspididae is designated as Quarantine Pest (the Plant Protection Law).
Introduced range in other countries South Korea, continental China, Hong Kong, Taiwan, Philippines, Vietnam, Thailand, Malaysia, Myanmar, Indonesia, India, Pakistan, Armenia, Italy, France, Australia, Fiji, etc.
Populations in Cheju Is., S Korea and Nice, France are assumed to be introduced from Japan.
Reference Notes
  • Ecol Soc Jpn (ed) (2002) Handbook of Alien Species in Japan. Chijinshokan, Tokyo (in Jpn)
  • Kohama & Takahara (2002) Exotic insects in Okinawa. Bull Okinawa Pref Mus. 28, 55-92 (in Jpn)
  • Korenaga (1999) One of the most serious insect pests of citrus: arrowhead scale, past and now. Nogyo-gijutsu. 54(4), 175-179 (in Jpn)
  • Nakao (1977) The arrowhead scale, Unaspis yanonensis, and its predators in the Ryukyu Archipelago. Jpn J Appl Entomol Zool. 22(1), 43-48 (in Jpn)
  • Ohkubo (2002) Present situation of the distribution of impoted parasitoids against arrowhead scale, Unaspis yanonensis Kuwana, and future perspectives on their potential for biological control. Plant Protection. 56(3), 106-109 (in Jpn)
  • Plant Protection Station (2011) The Plant Protection Act. Quarantine Pest List. (Accessed on 2012-3-15) (in Jpn)
  • Stan (2004-2012) (Accessed on 2012-3-15)
  • etc.
100 of the Japan’s Worst Invasive Alien Species

Althoug this species seriously infested in past, it has been suppressed to low density at present, by the development of control technique (biological control and pesticides). The effort to control is still continued.
In Okinawajima Is., this species was found in 1981 at Nago City, and controlled by several methods including biological control using parasitic wasps Aphytis yanonensis and Coccobius fulvus. Since 1989, this species have not been observed in Okinawajima.