Nacoleia octasema Minimize

September 2006. Makira, one of the islands of the Solomons, is famed for bananas. There have been collections of more than 100 varieties at a rural training centre on the coast, and 69 are presently maintained by a lady in the highlands. Scab moth, Nacoleia octasema, is sometimes a problem and growers would like to know of cultural control measures. Removal of the bracts is said to help reduce damage.

Bagging of the bunches was suggested, but for subsistence growers this is out of the question. Bract removal is hard work with little impact; besides, timing is important. Blowing ashes into the fruits by opening the bracts is a traditional method practiced in Samoa. Other than bagging and ash, chemical control is effective. Some work on the problem was reported from NARI, Keravat, East New Britain, Papua New Guinea.

A contribution from the Northern Territory Government, Australia made several interesting points. Sugar cane bud moth damage on bananas is also common and often confused with scab moth damage. The larvae and the damage can look similar to the untrained eye. If both are present together it can be confusing.

Scab moth enters the bell and begins feeding well before bract fall or even before the bracts can be successfully pulled off. It is highly unlikely that bract removal will work. Sugar cane bud moth comes in from the flower ends on the female fruit and early bract removal and flower end removal may help here. Removing the male bell as soon as possible after the last female finger has emerged helps prevent the scab moth larvae developing through to pupation as the male bell and the retained male bracts appear to be the preferred sites. If this is done routinely to all bananas in an area, it can reduce populations.

Bell injection with Chlorpyrifos or Omethoate is used very successfully in Queensland and elsewhere and gives complete control. Neem oil was tried some time ago and it gave control, but there was always some damage as it is an anti-feedant: the larvae had to feed to die. There are some excellent posters on control of scab moth.

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