Cotton red spider mite

Other names
Glover mite, Tetranychus gloveri

General information

Spider mites are so-called because they produce silk. Cotton red spider mite is a generalist species and has been recorded from over 100 different hosts throughout the Pacific and Americas.

In bananas, the mite is most likely to be found on the underside of older leaves, in dry weather and/or on stressed plants. This species is characterised by the red colour of female adult mites. Mites, eggs and webbing can be found along the midrib of the underside of the leaves.

Cause

Severe outbreaks could be associated with aerial or cover sprays of broad-spectrum insecticides. Outbreaks of spider mites are usually localised within a plantation.

Warm dry conditions favour mite populations and stressed plants can be more affected than others. Dry micro-climate conditions under plastic bunch covers could be particularly favourable for encouraging an increase in mite numbers.

Description

Appearance

Females

Adult females are usually less than 0.5 mm in length, have 8 legs and are barely visible to the naked eye. They are bright crimson red when alive.

Males

Adult males tend to have an orange tinge, and immature mites range from greenish to brownish as they mature.

Eggs

Cotton red spider mites lay colourless eggs. The eggs of other spider mites found on banana (e.g. T. lambi and T. urticae) are also clear when first laid and often become yellow-orange before hatching.

Distribution

These mites have been recorded on several hosts in the Northern Territory. To date, they have only been detected on bananas and some common weed species in the Wet Tropics region in North Queensland. The full extent of the distribution in Australia is unknown.


Lifecycle

The small round colourless egg is followed by three immature stages. These are similar to the adult stage, though a different colour (see above).

The life cycle can be completed in 1-4 weeks, depending on temperature. There are many overlapping generations each year.

All stages of the life cycle plus cast skins, dead mites, and dark faecal droplets occur together, mostly near the veins of the underside of leaves. With high numbers, they can extend over the whole leaf and possibly the fruit.

Crop(s) affected

Cotton red spider mites have been recorded on crop species including banana, cotton and papaya.

Host(s)

Host species include: banana, cotton, beans, eggplant, beetroot, peas, sweet potato palm trees, papaya and many other ornamental and weed species.

Symptoms

Spider mites repeatedly puncture plant cells and suck out the cell contents causing cell death and breakdown. In bananas:

  • damage is mainly confined to the underside of lower older leaves, near the midrib. Webbing is also noticeable along the midrib.
  • in severe outbreaks, mites can be found on all leaves and it is possible mites could move onto the banana bunches and damage fruit.
  • leaf damage first appears as isolated white flecking and sometimes rusty patches close to the leaf midrib.
  • eventually the whole leaf turns brown-grey and, in extreme cases, the leaves wilt, with partial or total collapse of the leaf skin.
  • leaf wilting and collapse result in sunburnt bunches and reduced plant growth.

Impacts

Monitor crops at least fortnightly during hot dry conditions and every 3 weeks at other times. Apply a miticide treatment to prevent damage if mites are found on the young leaves and dry to hot conditions are expected. Miticides are most efficient if applied early in the infestation.

Spread

Mites are spread by wind, on clothing and equipment.

Risk period

Populations increase rapidly in hot dry weather and favour dusty conditions.

Monitoring and action

Preventing infestation

  • Reduce dust on roadways.
  • Maintain good weed control as broad-leafed weeds act as reservoirs for mites, which can then re-infest banana crops
  • Reduce water stress to plants through good water management practices. Healthy plants will better withstand mite damage.
  • Regularly trim leaves and maintain correct plant densities to assist with good spray coverage and to increase the level of control obtained with miticides.

Monitoring plants

  • Check plants regularly.
  • Only treat with pesticides if mites are present.
  • Check older, lower leaves for the presence of adult mites and their silk.
  • Check newer leaves for immature mites. A spray may be required if:
    • mites are detected
    • natural predators are not evident, and
    • dry and hot weather conditions are expected to continue.

Control

Control is the same as other spider mites. In general, spider mite activity is mainly confined to dry periods, and specific miticides may be required during these times. High humidity does not favour spider mites and mite populations in north Queensland tend to reduce in the wet season.

Biological

The small, shiny black mite-eating ladybird beetle predator, Stethorus spp. is the most important predator of plant-feeding mites in bananas. Both larvae and adults feed on the mites. The black pupae of the ladybird may be seen as a line on either side of the midrib when mite populations are high.

Other predators include:

  • other ladybird beetles
  • native predatory mites
  • predatory thrips
  • rove beetles.

Chemical

Spray with a miticide only when plants are not suffering heat/moisture stress. If leaves are wilted or plants are small, coverage of the mites on the under-surface of leaves is difficult. Do not exceed recommended rates and volumes or fruit 'burn' may result.

For good chemical mite control:

  • ensure miticide treatments are well-timed and use correctly calibrated sprayers or misting machines
  • apply at least 500 L/ha to obtain good coverage of leaf under-surfaces where the mites occur
  • apply a second application 14 after the first, especially if monitoring indicates a carryover of mites. Use a miticide with a different mode of action at or before 30 days to avoid resistance in the next mite generation. A second and subsequent applications may not be required if:
    • a thorough first application of an ovicidal miticide was applied
    • high populations of Stethorus lady beetles are found during monitoring after the first treatment
  • avoid using the same miticide more than twice per season
  • avoid using broad-spectrum insecticides such as synthetic pyrethroids and neonicotinoids as these will also destroy natural predators and stress the plants which can increase spider mite populations.
  • Chemical registrations and permits
  • Check the Australian Pesticides & Veterinary Medicines Authority chemical database and permit database for chemicals registered or approved under permit to treat this pest on the target crop in your state/location. Always read the label and observe withholding periods.

Chemical registrations and permits

Check the Australian Pesticides & Veterinary Medicines Authority chemical database and permit database for chemicals registered or approved under permit to treat this pest on the target crop in your state/location. Always read the label and observe withholding periods.

Quarantine restrictions

Avoid moving infested plants.

More information

Last updated 10 December 2014