Spider mites – house plant diseases

February 4, 2016 at 5:27 pm

spider, tetranychus urticaeIf the leaves of your plant are drying out and you can see a fine spider’s web under them then the flower has probably been infested by the spider mite – the most common pest to prey on house plants.

How to recognize it

spider mite

By J. Holopainen (From my camera), CC-BY-SA 4.0, via Wikimedia Commons

Description of the spider mite

The spider mite is a member of the mite family Tetranychidae. The species red spider mite (tetranychus urticae) is the most common one to be seen indoors.

It is a small spider about 0.5 mm (0.02 in) long, yellowish, light brown or reddish (in winter). On leaves it is visible to the naked eye as a little slowly moving spot (if it is standing still, it is enough to touch it for it to start to move).

 

Appearance of the infested plant

Spider mites feed on the leaves of the infested plant, sucking sap from them and causing the emergence of light yellow patches. After some time the leaves curl, dry out and finally drop off.

A typical sign of spider mite infestation is a spider’s web attached to the bottoms of the leaves, on which you can spot small spiders moving around. In the initial phase of the infestation it is vestigial, then, as the disease progresses, it becomes more noticeable.

Yet, from the very beginning of the infestation, you can notice on the leaves tiny spots moving around which, under a magnifying glass, turn out to be small spiders.

 

spider mite web

Spider mite web
Photo by RasbakOwn work, CC BY-SA 3.0, via Wikipedia Commons. Modification (zoom window) by Łukasz Dumiszewski / MyHousePlants.com

 

Causes of infection

Where can the spider mites on your plant have come from? You can bring them home on a newly bought flower, they can get into your home from outside, or move over from another, already infested plant. The flowers particularly exposed to spider mite (or other insect) infestations are those which have become weakened or are grown in unfavourable conditions.

Here I would add that warm, dry air favours the appearance of spider mites. Maintaining a certain level of humidity (e.g. by sprinkling the house plants) can prevent infestations from occurring.

Many house plants can be a target of the spider mite. In my case the bug appeared, among others, on the ficus benjamina, miniature rose or dieffenbachia.

How to fight it

Prevention

The best thing is, of course, prevention. Providing your plant with suitable conditions will make it healthier and more resistant to infections. House plants, like all living things, are the more prone to diseases, the weaker their physical condition.

In the case of the spider mite it is important to guarantee the proper level of air humidity for the plant. As I already mentioned, the probability of the spider mite’s appearance is higher in a warm dry room (which is often the case when the heating is on in the winter). To raise the air humidity, sprinkle the plant with water every so often, place the pot saucer in a wider one, filled with water, or put the plant alongside other plants. Of course, don’t do this in the case of plants that prefer drier air like, for example, succulents.

How to fight it – the traditional method

If the plant has been infested by the spider mite, you should take action immediately, before the colony becomes too big and any damage to the plant is serious. Buy a proper treatment in a spray form (you should be able to get it in any good gardening centre or even in some florists’) and sprinkle the infested plant with it according to the instructions. You will most probably need to repeat the procedure a few times, every few days. I am sure that this will help – modern chemical insecticides are very effective.

Insecticides are not usually without effect on people and animals, so take precautions while using them, particularly if there are children or pets in your home. You should follow the instructions that come with the treatment strictly.

How to fight it – natural methods

You can also try to fight the pest by applying so called natural methods. Firstly, these tend to be more eco-friendly, and secondly, you may already have what is required somewhere to hand.

In the case of the spider plant some sources recommend washing the infested plant with warm water, sprinkling it with a solution of tepid water mixed with soft soap, or introducing predatory mites (there are places where you can buy so called beneficial organisms, even by mail order).  

I must admit that I have never had enough patience to use methods like these and after a few failures I switched back to the common chemical treatments that are sold in shops. More and more of these are now made from natural compounds, however, some of them can turn out to be not as effective as the strong chemical agents.

If you want to try some alternative methods of fighting the spider mite, you will find a lot of advice on these sites:


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Łukasz Dumiszewski

A computer scientist who likes house plants and who once wanted to be a writer. A blogger who writes about his experiences in growing house plants by using the benefits of computer science. 😉

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