Spots on fruit

Note slightly sunken black circular spots up to 5 mm in diameter. Inset: banana spotting bug (about 2 cm long).

Banana spotting bug

Cause: Feeding (sucking) by banana spotting bug, Amblypelta lutescens lutescens, usually on the exposed outer curve of the fingers.

Solution: Damage is more severe on blocks adjacent to rainforest. No specific treatments required. If more than 5% of bunches are affected, spot spray.   

Fruit speckle

Cause: The fungi Colletotrichum musae, Fusarium oxysporum and Fusarium semitectum. Spores are produced in large numbers on dead leaf material during wet conditions and are spread in air currents to the fruit.  

Solution: Fruit speckle is generally a minor disease in well managed plantations that use a leaf spot spray program.  

Note stings (minute pinholes) on the surface. A small drop of sap usually forms at the sting site.

Fruit flies

Cause: Banana fruit fly, Bactrocera musae, and Queensland fruit fly, Bactrocera tryoni, laying eggs (stinging) in the pulp of banana just below the skin. The banana fruit fly can sting green fruit but the Queensland fruit fly only stings ripening or yellow fruit.   

Solution: Chemical control should not be required since fruit is harvested at the hard green stage before either of the fruit flies can complete their life cycles. Do not leave over ripe fruit in the field. If mixed ripe fruit causes hot spots in the plantation, spot spray with an appropriate chemical. 

Note raised 'pimples' on the skin.

Flower thrips

Cause: Scarring from egg-laying by flower thrips, Thrips hawaiiensis on young fruit when still covered by the bracts.

Solution: Insecticide injection at bell emergence for control of scab moth also controls flower thrips. 

More info:
Banana flower thrips – general information 

The spots or rings are usually on the lowest points of fingers where chemical runs if the bunch is oversprayed.

Spray burn

Cause: Spraying with excessive volumes of chemical or inappropriate chemical use. 

Solution: Use only registered chemicals and apply according to the label directions.

Sooty blotch

Cause: The fungus, Chaetothyrina musarum (formerly known as Chaetochyrena musarum)plus various fungi (moulds/mildews) growing on dead plant material during moist weather. 

Solution: Lady Finger and Ducasse are more prone to sooty blotch than Cavendish-type bananas. A post-harvest dip of sodium hypochlorite at 100 ppm for 5 minutes followed by immediate rinsing, is highly effective in removing sooty blotch.

Sooty mould

Cause: Sooty mould fungi that develop on the honeydew secretions of the banana aphid, Pentalonia nigronervosa.

Solution: Natural control by parasites and predators provides adequate suppression. Infestations are more obvious during cooler weather in autumn and spring. Spot treatment with a suitable pesticide is occasionally required as the mould can be difficult to remove from fruit.