Taxonomic name: Banana bunchy top virus (BBTV)
Synonyms: Banana bunchy top virus BBTV
Common names: abaca bunchy top virus, banana bunchy top disease (BBTD), BBTV, bunchy top, bunchy top virus, laufeti’iti’i (Samoan-American Samoa)
Organism type: micro-organism
Banana bunchy top virus (BBTV) is a deadly pathogen which affects many areas of the world-wide banana industry. Infected banana plants produce increasingly smaller leaves on shorter petioles giving the plants a bunched appearance. Fruits may be distorted and plants become sterile before the whole mat (rhizome) eventually dies. The international spread of BBTV is primarily through infected planting materials.
Ferreira et al. (2001) describes the onset of BBTV: "The first symptoms consist of darker green streaks on the lower portion of the midrib, and later on the secondary veins of the leaf. Removing the "white fuzz" or wax covering the midrib makes it easier to see the streaking clearly. Streaks consist of a series of `dots' and short lines, often referred to as `morse code' streaking. As infection progresses, streak symptoms become evident on the leaf blade. When fruit is produced, some of the banana hands may have distorted and twisted fruit. Keikis or suckers that develop after infection are usually severely stunted, resulting in leaves `bunched' at the top of the stem. Leaves are usually short, stiff, erect and more narrow than normal. Leaves display marginal yellowing or chlorosis and necrosis or burning."
Symptoms are also described in detail by Thomas and Caruana (2000). The dot-dash symptoms and the dark green “hooks” seen as the streaks enter the petiole are most characteristic and are best viewed from the underside in transmitted light. A virus characterised by small (18 to 20 nm), isometric particles and a multi-component ssDNA genome has been purified from infected plants (Thomas and Caruana, 2000).
Coconut foliar decay virus (CFDV), Subterranean clover stunt virus (SCSV)
agricultural areas, host, vector
BBTV occurs in Musa (including banana, abaca, plantain and ornamental bananas) and Ensete in the family Musaceae. Although there are some reports of monocot hosts in related families, evidence is conflicting, and Musaceae are generally considered the only hosts (reviewed by Thomas and Caruana, 2000).
BBTV is transmitted by the aphid vector Pentalonia nigronervosa (Magee, 1927). The aphid spreads the virus through its feeding behaviour on susceptible species.
BBTV is a destructive pathogen in many banana-cultivating areas of the world (Su et al. 2003). The Hawaii's Department of Agriculture (1999) describes the affect of the virus stating, "Infected banana plants are stunted and produce small, deformed fruits. In advanced stages of the disease, plants do not produce any fruit. Infected banana plants are useless and serve only as a source of the virus. A tiny insect called the banana aphid spreads the disease by carrying the virus to healthy plants after feeding on infected plants." Banana-production is usually unprofitable in areas severely affected by BBTV, though disease incidence may be low in adjacent sites.
Known introduced range: Africa, Asia, and the Australasia-Pacific region. (Kenyon et al. 1997; Sun et al. 2002; Wellings et al. 1994)
Introduction pathways to new locations
Transportation of habitat material: Magnaye and Valmayo (UNDATED) report that, "The international spread of BBTV is primarily through infected planting materials (Wardlaw 1961)."
Local dispersal methods
Horticulture (local): Where the incidence of BBTV is low the virus is mainly spread by planting diseased suckers.
On animals: Manickam et al. (2001) report that BBTV can be transmitted from infected to healthy bananas by the aphid Pentalonia nigronervosa.
There are no resistant varieties of banana plant known. The Cooperative Extension Service (1997) believes that the most important methods to control BBTV involve, "killing the aphid vector (disease carrier) and roguing (removing and destroying) infected banana plants. By killing the aphids on the banana plant, dispersal of virus-carrying aphids to nearby, healthy banana plants is avoided. Since the only host of BBTV is banana, roguing infected trees reduces spread of the virus by reducing the opportunity for aphids to aquire the virus or for people to obtain and transport infected suckers or planting material."
The Cooperative Extension Service gives detailed instructions for controlling BBTV at home and in a commercial setting. Please refer to Cooperative Extension Service, 1997. Brooks (2000) also offers detailed step-by-step instructions to homeowners and commercial growers for the eradication of BBTV. Please refer to Brooks, 2000.
For details on chemical, physical, biological control options, please see management information.
The Cooperative Extension Service (1997) states that, "Banana bunchy top virus is spread by the banana aphid, which acquires the virus after at least four (but usually about 18) hours of feeding on an infected plant. The aphid can retain the virus through its adult life, for a period of 15-20 days. During this time, the aphid can transmit the virus to a healthy banana plant by feeding on it, possibly for as little as 15 minutes but more typically for about two hours."
To become infective, the aphids require a feeding period of at least 4 hours or more on diseased host plants. To transmit the virus, infective aphids require a minimum feeding period of 15 minutes on susceptible plants, though efficiency of transmission increases with longer feeds (1.5 to 2 hours) (Hu et al. 1996, Magee 1940). Magee's experiments indicated that an average of about 25 days incubation is necessary for the development of banana bunchy top symptoms. He also found that young, newly infected plantlets are a better source of virus than adult plants and that nymphs are more effective vectors than mature aphids.
This species has been nominated as among 100 of the "World's Worst" invaders
Reviewed by: Dr John E Thomas
Senior Principal Plant Virologist, Horticulture and Forestry Science
Department of Primary Industries and Fisheries Queensland Australia
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Wednesday, 6 July 2005