Spider mite & two-spotted mite in bananas
Bruno Pinese & Rod Elder, Department of Primary Industries and Fisheries.
Description
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Banana spider mite (Tetranychus lambi) damage |
Two-spotted mite (Tetranychus urticae) damage. Note the silvery-grey damage to the tip of the fruit fingers |
Adult
Adults are usually less than 0.5mm in length, have 8 legs and their spider-like appearance can just be made out with the naked eye. Under a x10 hand lens the active form of two-spotted mite appears translucent, greenish, and has two conspicuous black spots on the body. Under adverse conditions the two-spotted mites become reddish-orange. The banana spider mite is more straw coloured and lacks spots. The main distinguishing feature between the two species is the lack of fine webbing in infestations of the banana spider mite.
Immature stages
The clear, very small spherical egg is followed by three immature stages that are similar to the adult stage.
Life history
The life cycle of both species can be completed in 1 to 4 weeks, depending on temperature and there are many overlapping generations each year. Populations increase rapidly in hot dry weather. All stages of the life cycle plus cast skins and dead mites occur together, mostly near the veins of the underside of leaves but with high numbers can extend over the whole leaf and fruit.
Distribution
Throughout Queensland.
Host Range
Two-spotted mite has a wide host range, consisting of broadleaved weeds, grasses, and crop plants such as strawberries, stone fruit, apples, pears, beans, tomatoes, cotton etc. and ornamentals such as roses.
Management
Importance
Mites are a minor and frequent pest of bananas.
Banana spider mite is the most important and widespread of the mite pests of bananas. Two-spotted mite has only been recorded occasionally. These 2 mite species are very similar but two-spotted mite produces copious webbing when numbers are high and banana spider mite does not produce significant webs. Activity is mainly confined to the dry spring to summer periods where specific miticides may be required. High humidity does not favour mites and mite pressure in north Queensland reduces accordingly in the wet season. Severe outbreaks are usually associated with aerial or cover sprays of broad-spectrum insecticides. Outbreaks of the mites are usually localised within a plantation. The warm, dry conditions under plastic bunch covers are particularly favourable for build-up of banana spider mite.
Damage
Mites suck out the cell contents causing cell breakdown. Damage is mainly confined to the underside of lower older leaves; however, in severe outbreaks the mites can move onto the bunches and damage fruit. Leaf damage appears at first as isolated rusty patches, which later coalesce along the leaf veins as the infestation increases. Eventually the whole leaf turns brown-grey and, in extreme cases, the leaves wilt, with partial or total collapse of the leaf lamina. Leaf wilting and collapse result in sunburnt bunches and reduction in plant growth.
Fruit damage by banana spider mite is found mainly on the cushion end of the fingers close to the bunch stalk. Feeding in this area causes a dull red to purple-black discolouration of the fruit surface that may later dry out and crack
Two-spotted mite damage to fruit is usually confined to the top of bunches, and develops as silvery-grey patches on the tip of the fruit fingers.
Action level
Monitoring should be carried out fortnightly during hot dry conditions and at intervals of three weeks otherwise. Action thresholds have yet to be determined, but if mites are found on the young leaves and dry to hot conditions are expected, a treatment should be applied to prevent damage. Miticides are most efficient if applied early in the infestation.
Control methods
Cultural
Reduce dust on roadways as much as possible because dusty conditions favour build-up of mites. Broad-leafed weeds act as reservoirs for mites, which can infest banana leaves following treatment. Ensure a good level of weed control is maintained to reduce this.
Good water management, especially during dry conditions, will reduce water stress to plants, allowing them to better withstand mite damage.
Regular desuckering, leaf trimming and maintenance of correct plant densities will assist in achieving good spray coverage and thus increase the level of control obtained with miticides.
Biological
The small, shiny black mite-eating ladybird-beetle predator, Stethorus spp. is the most important predator of mites in bananas. Both larvae and adults feed on the mites. When mite populations are high the black pupae of the ladybird may often be seen as a line on either side of the midrib. Other predators include other ladybird beetles, native predatory mites, predatory thrips and rove beetles. Releases of the predatory mite, Phytoseiulus persimilis, in bananas have not been successful against the banana spider mite in northern Queensland.
Cover sprays with broad-spectrum insecticides are the major cause of mite flare-up because they destroy the natural predators. Some fungicides used to control leaf disease in bananas also effect the predators. Where non-disruptive (pest-selective) pesticide treatments are used, natural predators usually provide sufficient control and miticides should not be required.
Chemical
A spray may be required if there is noticeable bronzing on young leaves (leaf No.3 and above), if natural predators are not evident and if dry and hot weather conditions are expected to continue. Spray only when plants are not suffering heat/moisture stress, because if leaves are wilted, coverage of the mites on the undersurface of leaves is difficult. Do not exceed recommended rates and volumes or fruit 'burn' may result. Good mite control can be achieved by well timed miticide treatments using correctly calibrated sprayers or misting machines. Sufficient volume (up to 500 L/ha) has to be applied to obtain good coverage of leaf undersurfaces where the mites occur. In most situations a second application 14 days later should be applied, especially if monitoring indicates a carryover of mites. This second application may not be required if a thorough first application of an ovicidal miticide was applied, or if high populations of Stethorus lady beetles are found during monitoring after the first treatment.
Recommended chemicals
clofentezine, dicofol, fenbutatin oxide, propargite,
pyridaben.
Note:
This information was correct at the time of publication. However it is the
user's responsibility to ensure that only currently registered agricultural
chemicals are used and that they are used in accordance with legal requirements.
Always read the label.
Further information
- Infopest CD-ROM contains current national information on registered agricultural chemicals and is available from Infopest, DPI&F, GPO Box 46, Brisbane Qld 4001 or by email from infopest@dpi.qld.gov.au
- Pinese, B. and Piper, R. (1994) Bananas: Insect and mite management. Department of Primary Industries, Brisbane.
- Swaine, G., Ironside, D.A. and Corcoran, R.J. 1991, Insect pests of fruit and vegetables, 2nd Edition, Queensland Department Primary Industries, Information Series QI91018.
- Agrilink Tropical Banana Information Kit provides information on all aspects of growing and marketing tropical bananas in Queensland. It is available from the Agrilink website or office (phone 1800 677 640) or the DPI&FShop On-line.
- DPI&F Business Information Centre on 13 25 23 - local call 8 am to 6 pm Monday to Friday (non-Queensland residents phone 07 3404 6999). E-mail: callweb@dpi.qld.gov.au
Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries and Fisheries, Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.
Last updated 04 February 2004