Environment

Stop the Bunchy Top

Tuesday, August 2nd, 2011

Community contributed by Glenn I. Teves, County Extension Agent

Banana Bunchy Top Virus (BBTV) has again reared its ugly head in Ho`olehua. Named after its characteristic choking or bunching of the leaves at the top of the plant, BBTV is the most destructive disease in bananas. Other disease symptoms include a dwarfing of the plants with skinny leaves having yellow or burnt leaf edges bunched together. On the lower portion of the leaves, there are dark green streaks on the mid ribs and also dots and dashes that look like Morse code. The Morse code will move down the mid rib at the attachment to the plant. Fruits are usually stunted, twisted, and distorted.

The hot spots include the new subdivision near Lanikeha, upwind from where it was originally found several years ago, and also around Kualapu`u town. To date, this disease has been confined only to Kualapu`u and Hoolehua. Ginger and heliconia, relatives of banana, are known hosts of this disease but we haven’t seen any diseased plants on Molokai.

The virus is spread by the banana aphid. Just by feeding on an infected plant for 18 hours, the aphid can spread this disease for two weeks. By feeding on a new plant for just two hours, the plant can be infected. Banana plants downwind from the hot spots are especially susceptible to new infections since aphids are not good fliers and will usually float in the wind, with the exception of winged types, called alates, which are usually rare.

The banana variety Chinese or Dwarf Cavendish banana is the most susceptible to this disease. Dwarf Brazilian or Dwarf Apple Banana is more tolerant to it. If you suspect BBTV infected plants in your yard or homestead, do not handle or move the plants. Viruses are systemic; once one plant in a mat is infected, it infects all the plants connected to it. If left untreated, it’s only a matter of time before all the plants in that specific area are infected. The key to controlling the disease is by controlling the banana aphid.

All plants near the infected plant must be treated with insecticides to control the aphid and prevent it from moving from infected to healthy plants. Only after plants are treated can they be moved and destroyed. Complete removal is essential, including killing all plant parts through the use of an herbicide. Treating symptomless plants with insecticides near the hot spot is vital to stop the spread of the disease.  If regrowth occurs from the diseased area, these plants will also have to be treated and destroyed since they still carry the disease.

There is a quarantine prohibiting the movement of banana plants and plant parts, except fruit, from Oahu to all neighbor islands have been imposed. It is only through the vigilance of the community that we’ve been able to keep this disease out of Molokai for so long. For more information on BBTV, check out the UH CTAHR website. http://www.ctahr.hawaii.edu/oc/freepubs/pdf/CFS-BAN-4A.pdf
If you suspect your trees may have the disease call Molokai/Maui Invasive Species Committee at (808) 553-5236 ext. 6585 or (808) 336-0625.