The coconut mite is serious pest of coconut.This pest is not currently reported in the Pacific although similar symptoms have been noted.
The adult coconut mite is tiny, only 200 – 255 micrometres (1/1000 of a millimetre) long by 30 – 52 micrometres wide. You can not see it with the naked eye.
A 10x hand lens will be needed to see colonies and individuals which will appear as silver patches.
Higher magnification (microscope) will be needed to identify this species.
They are especially hard to see as they live under the leaf-like structures (bracts or perianth) that support the fertilised female flowers, or in this case the nut.
They do not infest unfertilised flowers as these do not allow enough space to enter under the perianth.
The coconut mite has 4 life stages completed within 7 -10 days. These stages are adult, 2 x larval stage and egg.
The female can lay around 30-50 eggs into colonies. The egg stage last 3 days.
Nymphs look like the adult with the same pale colour and features but smaller. Each larval stage last around 2 days.
Adults are pale in colour with long and slender bodies that appear worm-like. However, they have two pairs of legs.
A colony of coconut mites under a microscope. Adults have two pairs of legs (© James V. DeFilippis, University of Florida)
Both the nymphs and adults cause damage to the nut.
The initial signs of coconut mite damage is under the perianth (leaf-like structures at the top of the nut where it connects to them stem) where the mites shelter and feed.
Pale yellow, triangular patches or a broader zone of colour will form from the feeding. They can be seen coming out from underneath the perianth. After a few days these pale areas will turn brown (see image top right).
Growth of the nut may also look uneven if the feeding from mites is concentrated on one side or section of the nut.
The damage is most noticeable on the young green coconut. As they are maturing, the brown area will become larger and will be covering up to two thirds of the nut.
This damage may look rough and cork-like with long narrow splitting down the nut and cracks across it, as it becomes older and is exposed to air.
There may also be signs of a gum like substance oozing from the damaged surfaces.
Feeding damage can be severe when populations are high. The growth of the nut will be stunted and may fall before maturity.
Mite populations can decline after 6 months. Damage also declines, suggesting the mites prefer feeding on the young coconut.
Surveys of coconut mite damage and its impacts are sparse. However, it is estimated damage to nuts can range from 7.5 - 60% or more.
With the stunted growth and early nut fall, yields are greatly reduced. Losses to copra production are estimated to be 20-30%.
The appearance of the damage is considered unappealing and is likely to reduce sales of green drinking nuts. It has also been reported that dehusking damaged coconuts is difficult and requires more labour, furthering losses to growers who have to pay employees more.
Although the damage is not easily seen from a distance, the coconut palm is often used as an ornamental plant around tourist attractions and homes where they can be viewed up close.
The coconut mite is found in Asia, Africa, America (Central, North, South and the Caribbean) and Europe.
To find out what countries the mite is present in, see the distribution spreadsheet.
Initial symptoms of pale yellow triangular areas underneath the perianth (© James V. DeFilippis, University of Florida)
Damage concentrated to the left side under the perianth causing uneven growth of the nut (© Forrest W. Howard, University of Florida)
Enlarged brown area, cork-like with long narrow splitting and cracks (© Scot Nelson, Flickr)
Most importantly, the International Guidelines for transfer of coconut germplasm should be strictly followed to prevent pests and diseases being moved to new locations.
Prevention can be difficult with the coconut mite being so small and hidden under the perianth. Assessment of abundance is considered highly difficult and time consuming. However, techniques have been described in Faleiro et al (2016) Integrated Pest Management (IPM) of Palm Pests.
The spread of coconut mites can be rapid due to their ability to produce high populations with development from egg to adult in 10 days.
The mites also spread through wind allowing it to start new populations easily.
For general information on preventing pests and diseases of coconut, see the Prevention section of the website. The international guidelines for transfer of coconut germplasm should be strictly followed to prevent the spread of the pest.
We strongly recommend an integrated pest management (IPM) approach to the control of all insects, where possible. This is a combination of methods (pesticides, physical controls such as site hygiene, and biological controls) to minimise the use of pesticides and minimise the cost of control.
Integrated Pest Management (IPM)
The goal of IPM is to keep pest populations to a level below which they cause economic harm. IPM involves using multiple control options together for the economic control of pests (i.e. cultural, natural and chemical).
In an agricultural context the Food and Agriculture Organization defines IPM as "the careful consideration of all available pest control techniques and subsequent integration of appropriate measures that discourage the development of pest populations and keep pesticides and other interventions to levels that are economically justified and reduce or minimize risks to human health and the environment. IPM emphasizes the growth of a healthy crop with the least possible disruption to agro-ecosystems and encourages natural pest control mechanisms".
It is recommended to cut infested coconuts at regular intervals throughout development to get rid of mites. However this will impact production. Where coconuts are part of tourist attractions, this is recommended as damaged nuts can easily fall and cause injury.
Collecting the affected immature nuts that have fallen, and then destroying them by burning can help stop the spread of mites.
Positive and negative influences (such as nutrients) on mite infestations have been studied but have opposing results. Therefore, more research in to economical cultural methods is needed.
Planting coconut varieties that are resistant to coconut mites are recommended. Susceptible types to avoid are Jamaica and Panama Tall, Malayan - Golden, Green and Yellow Dwarf.
Some introduced varieties have nuts shown to have more tolerance to mite attack and include Equatorial Green, Malayan and Cameroon Red Dwarfs and Polynesian and Rennell Tall.
The coconut mite does have natural predators. These include many predatory mites in the Phytoseiidae family such as Amblyseius and Neoseiulus species. However, coconut mite populations still flourish even when predators are present, suggesting they are not effective as a control.
This is due to their habitat under the perianth, the mites are not easily preyed upon by predators. This may only occur when they are moving from one host to another.
Hirsutella thompsonii and Verticillium lecanii, pathogenic fungi used in mycoacaricides (fungus-based mite pesticides), have been effective in controlling the mites. They are readily available for purchase online and from plant stores.
Chemical control is not recommended when it can be avoided. It may not be beneficial and is generally difficult and costly to apply. The use of chemical controls will depend on the regulations within your country.
If necessary, most chemical applications are alternated with neem oil treatments once a year. It is recommended to harvest mature nuts before application of chemical controls.
A more natural method is applying a 2% neem oil and garlic emulsion. 10 litres of this emulsion can be made at home. The ingredients are: 200 ml neem oil, 200 grams garlic and 50 gram ordinary bar soap.
- Dissolve the soap by slicing it and putting it in 500 ml lukewarm water.
- Take the extract from 200 grams of ground garlic and place in 300 ml of water.
- Add the soap solution (500 ml) slowly in to the 200 ml neem oil. To get a good emulsion, stir forcefully.
- Stir the garlic solution in to the soap and neem oil emulsion.
- Add 9 litres of water to dilute the full 1 litre emulsion.
You should now have 10 litres of 2 % neem oil + garlic emulsion. This can be applied by a hand sprayer (1 litre) at intervals of 45 days.
Mature palms will require a climber or 'cherry picker' for application. The spray is applied to the top six branches during dry, non windy seasons (for safety and to avoid contamination).
Make sure to take all safety measures such as wearing protective gear and washing after spraying.
Wash face and hands cleanly with soap after spraying.
Always follow the instructions when using pesticides to prevent damage to the plant and natural predators.
CABI. 2018. Aceria guerreronis (coconut mite). [ONLINE].
Faleiro et al. 2016. Integrated Pest Management (IPM) of Palm Pests. Integrated Pest Management in the Tropics, pp. 458-462
Howard et al. 2001. Insects on Palms. Cabi Publishing. pp. 230 - 327.
Plantwise. 2018. Coconut mite (Aceria guerreronis). [ONLINE].
SAARC Agriculture Centre. 2014. Mite Management of Coconut in SAARC Member Countries. pp. 1-154.
TNAU. 2018. Pest and Disease Management; Coconut eriophyid mite: Aceria guerreronis. [ONLINE].
Howard and Moore (UF). 2016. Featured creatures; a coconut mite. [ONLINE].