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Treating Spider Mites Effectively (House Plants & Garden Plants)

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Spider mites under magnification
Red Spider Mites under magnification

The dreaded Red Spider Mite I can think of nothing more soul-destroying than getting Red Spider mites on your plants. The horror of horrors… how could anyone who has been growing plants for a couple of years not know of this terrible affliction? Easy, Very Easy!

The first issue is that these mites are extremely small so unless you’re really looking for them it’s very easy to miss them. Also, If you are new to gardening you may not know what to look for.

Worry not, by the time you finish reading this article you will know exactly how to identify if your plants are suffering from spider mites and how to deal with them and prevent them from returning.

You are in the right place I have you covered!

With just over 1200 species around the world, spider mites can be a pain for the gardener, They are small and live on the underside of leaves so are hard to spot. They spin fine webbing for protection, Damaging plants by piercing the leaf cells to feed.

Table of Contents

    What Are Spider Mites

    When I first started gardening I had no clue what spider mites were, however, I saw the signs left behind from the damage they caused. Read on to learn what you need to ensure that these tiny mites don’t ruin your plants at home. Here is what happened to me!

    Mea culpa. I brought a plant to a show that had evidence of these mites on the leaves. How could you do such a thing you may well ask?

    The answer is simple… I had never seen them, didn’t know what they looked like, was unaware that my insecticide was little or no use against them, and despite asking more expert growers than me, was still as ignorant of the pest as when I started.

    Suddenly, I was introduced to the Red Spider Mite and Two-spotted spider mite. I had no idea how to deal with these problems and both these mites were sucking the life out of my houseplants and the vegetables that were growing in my garden.

    Not knowing what these spider mites were and how to identify and find them I decided to do some research. Over the past 40 years, I have gained a lot of information and combated and won many spider mite outbreaks.

    What color are spider mites?

    Most people would say RED of course. Some say they are black, some say green. Therefore if you are checking your plants you will know what you are looking for… or will you?

    This has got to be one of the biggest misnomers guaranteed to mislead the unwary. A RED SPIDER MITE for example is only RED at a certain stage of the year, after hibernation and in the springtime.

    The newly hatched mite is almost white (off-white/buff-colored); the adult can be almost white (but in varying degrees through to green) with two spots on its back, looking like a saddle.

    These spots are said to be very dark green or very dark red, so dark that they could be taken for black.

    But these are only spots and not the whole insect. It is also known as the Twospotted Spider Mite. There is also another mite that is sometimes found on plants indoors and that is the Carmine Spider mite, but I haven’t seen that one yet, so I don’t know how it develops.

    What Are Red Spider Mites?

    They are tiny, crawling, wingless, insects (well actually they are arachnids for those who like to be pedantic about semantics) that have 6 or 8 legs depending on the stage of the development. Juvenile mites have 6 legs and the adults have 8.

    They are so small that they are invisible to the naked eye, and a magnifying glass is needed to see them. This is why most people are not even aware they have an issue until the leaves on their plants start turning yellow. If you imagine the full stop that I have just used they are more difficult to see than that.

    Red Spider mites
    Red Spider Mite

    Twospotted Spider Mite – Tetranychus urticae Koch

    The Twospotted Spider is an oval mite, ranging in color from translucent to brown but yellow is the main color they are found with. Given their name (twospotted spider mite) due to the two large spots on either side of the abdomen.

    These are found throughout Europe and the USA and can have outbreaks that can decimate the plants in your home.

    Spruce Spider Mite

    The Spruce Spider Mite is small and you will need a 20x magnifying glass or microscope just to see them, they also cause high levels of damage to Conifers, Balsam Firs, and Spruce which gives it its name.

    These mites can reproduce very quickly and only take a period of 5 to 8 days from spider mite eggs to breeding adult age. Infestations can occur quickly, especially during hot dry spells.

    What is the Breeding Cycle of Mites?

    Adults can lay eggs from only 36 hours old!!! The eggs are more easily seen with the magnifying glass as they are laid in small clusters, usually close to the veins of the underside of the leaf.

    You may also see the adult two-spotted female close by, as she will lay about 5/6 eggs every day.

    However, as I mentioned it speeds up dependent upon temperature. One account that I have read suggests that at 60 degrees she produces 20 offspring, at 70 degrees she and her offspring number 13,000, and at 80 degrees she represents a potential 13,000,000 individuals, and all within one month!

    This is clearly a major problem in the making, as the short breeding cycle (as little as 8 days from an egg to an adult breeding pest) combined with the early ability for the young to procreate, means that a massive infestation can arrive in a very small space of time. Hence the reason for the paranoia surrounding this pest!

    How Does the Hot Dry Atmosphere increase the Likelihood of Spider Mite Infestation?

    Simply speaking, the heat of the greenhouse speeds up the life cycle.Spider mite populations can explode very quickly. It can be as short as three days in hot places, and as long as a month in cool weather.

    So clearly temperature is key to the proliferation, along with a dry dusty atmosphere. As Greenhouses tend to be warming up considerably from April it is about this time that the breeding really gets going.

    Severe spider mite numbers are inevitable unless controlled and it will go on until autumn given the conditions when it tends to slow down as plants begin to take on dormancy.

    The remaining females will now turn RED (described by some as being more orange than red) and find places to hibernate.

    This is likely to be in the soil or compost of the host plant, in the bark of mature plants, or in the wood or brickwork of the building itself. Bear in mind they are extremely tiny so no crevice is too small for a winter home for them.

    They will re-emerge in the spring and will be bright red (or Orangey red). A cooler temperature and moist atmosphere are thought to slow down their metabolism and slow the reproductive rate so misting and capillary matting may help in control spider mites.

    Where should you look for Spider Mites On Your Plants?

    As with most pests, they will be found underneath the leaves so they have to really be looked for regularly. But you can’t see them, can you?

    On close inspection, you will see the effects of the eggs from above. The hatching young will eat away at the underside of the leaf, sucking the life out of the plant and this sometimes leaves a visible mark through and onto the top of the leaf.

    This may be yellowish or silvery and will be a small cluster of spots, each about the size of a full stop, and only by the fact that they are clustered does the mite give itself away.

    Most of us don’t notice mites until the infestation is established and the plant has been damaged. Leaves of affected plants seem to be drying out very quickly, which they are, as the mites suck the very life-giving sap from them.

    Dead and dried-out leaves fall and the plant begins to fade away. As the adults colonize the plant they may also spin a very fine web over the leaf and from branch to branch, and alas from plant to plant. At this stage, you must take drastic action.

    This also enables them to walk down the host plant across the compost, over the bench or floor, and up onto the next victim. Real serial killers these are.

    The webbing also tends to act as a shelter for the young underneath the leaf so that the effectiveness of sprays is considerably reduced.

    Spider mite

    Where do Spider Mites Come From?

    I trust most people know about the Birds and the Bees, so I won’t go into that except to say that insects bring in more disease and infestation than any other method, and big bees can do considerable damage to your carefully tended show plants in a very short space of time.

    You may be aware that the wild honeybee is itself under threat of extinction by a “mite” called “Varroor Destructor” which is attacking them.

    Therefore as the bees fly from plant to plant they are well capable of spreading other mites or viruses from infected to clean plants. Personally, I believe that white flies and aphids are the biggest cause of the spread of rust among plants, along with bees and wasps.

    Mites can be found worldwide and they are very adaptable to the conditions they arrive in. If we take our Honeybee scenario above, Imagine a beekeeper importing some honeybees from another part of the country to his colonies in the north.

    This just spread the mite’s home range by thousands of miles in one fell swoop. In today’s age, we are importing plants from all over the world and it is very likely that spider mites are being imported too.

    14 Steps To Combat A Spider Mite Infestation?

    1) It is about his time that a pair of kneeling pads becomes useful, as you may have to refer to praying before the problem is solved! Just kidding…

    2) Most importantly prevention is better than cure, as I have found to my cost. If you can cut off the source of supply then you are on your way to preventing an outbreak of whatever sort in your greenhouse.

    Place “bug screen” over open windows and doors to stop the ingress of pests, whilst still allowing air to circulate. You will almost certainly become aware very quickly of how effective this is in keeping down the number of insects getting at your plants in the first place.

    I replace whole sections of glass with this screen and this helps to keep the temperature down and the airflow up! Replace the glass in the greenhouse door with a screen and you can ignore the advice of “leave the greenhouse door open on hot days”.

    This will only let the blighters in. Keep the bees out and there is less chance of getting a Red Spider infestation.

    3) Remove any infected plants immediately… and if you can afford to lose the plant then burn it or get rid of it… don’t throw it into your compost bin as this may lead to re-infestation.

    You may be fortunate enough to get a “clean “cutting or two” before disposing of the plant, but let that be a lesson to you, and think of it as part of the learning curve.

    4) Check your plants regularly for any tell-tale signs… Pick the plant up and look underneath the leaves using your magnifying lens and you may see the Mites moving about, or eggs clustered.

    You will be on the lookout for other insects anyway so now use the magnifying glass and check for Red Spider as well. It may seem obvious but don’t buy infected plants. And DON’T bring infected plants to the plant sale.

    Do not be afraid to get out your magnifying glass and really check out any plants you are about to buy! It will save you a lot of time, effort, and expense in the long run. I, for one, will always carry my glass to plant sales in the future.

    5) Keep a generous space between plants to prevent mites from dropping from one plant to the next… This is true for most crawling pests too.

    This is probably the biggest fault that we “space-restricted” amateurs have. We always cram too many plants into our small greenhouse, or growing space, and thereby bring most of our problems upon ourselves.

    So how many plants is it possible to have in a 12 x 8 greenhouse? Good question. How does about 30 or 40 sound? One “Expert” I know tells me that you shouldn’t have more than a dozen, and perhaps that is too many.

    As a broad rule of thumb, one 5” pot will contain a plant 15” in diameter. If you leave a 3” gap between plants you will need about 18” square for each fully-grown specimen. Hence a 12 ft Greenhouse will take about 8 x 5” pots along the length.

    A 6” pot, therefore, requires 21” square and a 7” pot will need 2ft square, and so on… Easy to see how the space is quickly used up…

    Beneficial Insects Are One of the BEST Ways to Get Rid of Spider Mites!

    Tony O’Neill

    6) If you are lucky you will find the problem early and have a good chance of eradicating the problem… by simply squashing the mites and the eggs between the finger and thumb, but I find that this always tends to damage the leaf.

    7) You could try washing them off with a strong water sprayer. Some people use soapy water for this…but you should cover the surrounding area under the plant to catch any mites that fall from the plant as they could infect other plants.

    8) Improve the conditions in the greenhouse with more misting and cooler temperatures… this may be a bonus for Fuchsia growers as the harder you can grow the plants the better they seem to like it.

    If you can afford it, install a watering and misting system. Together with capillary matting & increasing humidity by hosing down the hot greenhouse floor, you will almost certainly keep mites at bay.

    Be careful about increased humidity as this can lead to botrytis if allowed to cool down too much, particularly at night. A cold humid atmosphere will certainly lead to increased botrytis problems.

    You need to strike a balance with regard to heat and humidity.

    9) Introduce Biological controls – predatory mites. These can eradicate red spider mites PDQ provided they are introduced early i.e. before the infestation is out of control.

    Other predatory mites feed directly on the Red Spider mites and will devour them at a rapid rate. The predators should gain control in about 4 weeks by which time they will have eaten all the Spider mites and then they become cannibals and eat each other until they too have all gone.

    A bit expensive I understand, but worth it if it puts you back in control. The secret here appears to be to introduce the predators before the problem gets out of hand.

    If you do use predators you will almost certainly have to stop using insecticides, as they will kill your precious beneficial insects as well. There is also a period to wait between your last spray and your first introduction to predators.

    10) Some people regard chemical sprays as less effective, but Polysect is reputed to be a good control against mites and other pests. Read the label carefully as you will see that differing strength mixes are required for the various pests.

    11) It may be possible to place sticky paper traps cut into strips around the pots to prevent the mites from emigrating from plant to plant.

    12) Hot pepper wax – which is sprayed to prevent transpiration – is another remedy that smothers the adults on the leaves, but does not kill the eggs so be prepared to repeat applications every 4 or five days until control is established.

    Mites need to expire a lot of moisture from their bodies to survive. If you can affect this you are well on the way to overcoming the problem.

    This Hot pepper wax is also a brilliant repellent to white, black and greenfly, as they do not like the Peppery taste of Cayenne! It also makes the leaves shine which is another bonus.

    Again a little expensive initial outlay but it goes a very long way so you don’t need much. I love this stuff! And it is perfectly “Organic”. The cayenne powder, sprayed onto the surface of the compost in your pots, is also reputed to deter crawling insects or sciarid flies, but I have yet to try this. Sciarid is a pest that I have very little trouble with anyway.

    However, it may just be an organic deterrent to Vine weevil crawling onto your pots so could be worth the try. (Just as an aside, the chopped & dried stems of tobacco plants are used by cage bird breeders to keep mites at bay.

    The stems are incorporated into the nesting material and create an inhospitable environment for the insects. If you grow tobacco plants,( nicotiana), then you only need to hang up the plants to dry as you would with any dried plant, and you will have your own supply.

    And in case you want to know –yes you can smoke the tobacco, but that can be the subject of another article. Nicotine in the form of snuff is also an insect deterrent when sprinkled on top of the compost – it must make them sneeze!

    Remember though that tobacco is high in nitrogen so if you are one of the very fussy people who make your own potions for compost it may upset the balance of your mix. Very little is needed and this should not be a problem.

    13) How many times have you ignored a mark or blemish on a leaf because there was no easily identifiable cause? I have. Sometimes the culprit has gone and is now doing damage elsewhere. Or is he… Perhaps he is just too small to spot.

    If you have a marked or damaged leaf take it off without too much disturbance. Chances are you will be getting rid of a major headache about to unfold.

    14) The Internet has some good articles if you want to go that far. Smothering the mites seems a popular method and may be worth the effort. I have taken these recipes from a website, and haven’t any reason to doubt their effectiveness.

    Spider Mite Sub-Family Species List For Bryobini, Hystrichonychini, and Petrobiini.

    NeoschizonobiellaBryocopsis Neotrichobia
    SinobryobiaTetranychopsis Schizonobiella
    PseudobryobiaMesobryobia Edella
    Eremobryobia Peltanobia
    Sub Species of Spider Mite Bryobini, Hystrichonychini and Petrobiini

    Spider Mite Sub-Family Species List For Eurytetranychini, Tenuipalpoidini, and Tetranychini

    Sub-Family Species List For Eurytetranychini, Tenuipalpoidini, and Tetranychini

    Spider Mite Damage to Plants

    Spider mite damage may be difficult to spot initially until the numbers increase. As time goes by that they are not spotted a spider mite infestation will occur and this is when the gardener will spot the symptoms of an outbreak.

    You will first see the signs of yellowing leaves at the base. On the underneath of the leaves will be a fine webbing. It is this webbing that forms a protection for the spider mites as they feed sucking from the cells of the flower or leaves.

    The leaves will turn from green to yellow or even grey. When gardening in your garden it is important to keep an eye out for the webbing when performing maintenance.

    Unless you catch this early enough a spider mite infestation can not only damage plants reducing their productivity but can also kill your plants at home.

    Damaged leaves due to spider mites

    Remedies For Spider Mites

    There are many Remedies for spider sites that you can buy. These include chemical sprays, insecticidal soaps, and Mechanical and Bioactivity.

    5 Easy and Natural Tips For Pest Pr...
    5 Easy and Natural Tips For Pest Prevention

    Mechanical Removal

    Mechanical is straight forward and that is a maintenance side of this process, Washing the leaves down with a spray of water can knock the twospotted spider mites to the ground, It raises humidity and this is not conducive to spider mites.

    Chemical, Insecticidal Soaps, and Bioactivity Treatments

    There are various purchased items for the treatment of mites. Being a natural and organic gardener I tend to air on the organic range of products, but if you are infested and cannot control them by any other means you may have to resort to a chemical formulation.

    SB Plant Invigorator is an insecticidal soap and is perfect for dealing with mites. I use this all the time, along with Neem. Consider looking out for both these products as they are both organic.

    Biocontrol of spider mites is also another popular method but can be a little more expensive.

    3 Homemade Spider Mite Insecticidal Recipies

    Spider Mite Spray Recipe No. 1

    For this natural spider mite spray, blend together the following
    ½ cup of starch or flour
    ½ cup milk
    1-gallon water

    When sprayed over the mites this mixture will trap them as it dries into a thin film. Repeat every 4/5 days until control is established. Check plants daily to ensure effectiveness. Dead mites will turn black so are much easier to see.

    Spider Mite Spray Recipe No. 2

    This is also a natural deterrent to uninfected plants and may help to keep mites and another pest at bay. It is also good to ward off Vampires.!
    ½ – 1-ounce Garlic
    2-3 ounces of onion
    ½ – 1 ounce of cloves
    ½ – 1 ounce of Cayenne pepper

    Whiz in your blender with 1 Cup of water till very fine.

    Add this mixture to one gallon of room temperature water. This natural spray must be repeated 3 times at 5-day intervals to kill off freshly hatched mites (the spray will not kill the eggs). If the mixture gets washed off it must be re-applied.

    Spider Mite Spray Recipe No. 3

    This is the favorite of the person who posted it on the website. It is a product called natural “Ultra-Fine”. This is a natural soap and phosphorous solution intended to specifically kill Spider mites and their eggs (as well as most other common pests) with just one spraying.

    Repeat after 10 days as a precaution in case you missed any the first time. I have been in touch with a guy in America to see if this is available in the U.K. but am still waiting for a reply.

    I will be on the lookout for this one, as it seems to be just what I/ we need!

    Once control is assured I think I will try the biological methods… perhaps a few Praying Mantis, which will eat every other insect known to us gardeners, and I think I know a lad around the corner who keeps them as pets. We may be able to do a deal…hmmm.

    The video below can help you when dealing with Spider mites

    Other Pests That Can Affect Your Plants

    Spider mites are a nightmare when it comes to damaging your plants, But there are so many more pests and diseases such as Whiteflies, Fungus Gnats, Hornworms, Termites, Rats, Blackflies, Aphids, Allium Leaf Miner, Ants, Thrips, Slugs, and Flea Beetles, just to name a few.

    Learning what each of these pests is and how to deal with them can greatly increase your chances of having a successful garden.

    Conclusion On Dealing With Spider Mites

    It is important to remember, that prevention is better than cure.
    Don’t just pick up a plant and bring it home. Check for any signs of Spider mites and if you see it leave the plant in the nursery.

    Take your magnifying glass with you when you are going to buy plants – no matter where from – and check them thoroughly.

    Try not to move plants in and out of the greenhouse as you could be carrying in the latest infestation. Perhaps replacing sections of glass with a bug screen will increase airflow and keep temperatures down whilst also keeping the insects out. This is a difficult one, as most of us do tend to carry plants into the greenhouse even to just work on them. Perhaps a separate area is needed.

    I hope this article is of help to others like me, who know very little about Spider mites and have a chance to learn before the problem arises.

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