Plumeria are great tropical plants for the home, garden or greenhouse, but they have a whole range of pests that can cause lasting damage, and a spider mite infestation is one of the worst. The humble spider mite, uses the plants as a host for webs, reproduction, and water, making it essential to know exactly how to get rid of spider mites before they cause irreversible damage to plumeria trees.
Common non-organic insecticides are not safe for use in any garden and have lasting effects on wildlife, so we’re going to explore their natural enemies, and organic alternatives to toxic insecticides for spider mites, and hopefully, help you revive your prized plumeria in the process.
What are Spider Mites?
Spider mites are a species of arachnid, closely related to spiders, but often mistakenly to referred as insects. As part of the arachnid family, spider mites look, move, and live in very similar ways to spiders and ticks, spinning silk webs to protect their young, rather than catch prey.
Unlike spiders, the spider mite feeds on chlorophyll, so spin webs are almost exclusively for protecting their young. Chlorophyll is heavily present in plumeria and is important for plumeria plants to maintain healthy green leaves, so spider mites are major pests on this beautiful tropical plant.
There are two common species of spider mite that predate plumeria indoors and outdoors; the red spider mite, and the sixspotted spider mite. Both are effective pests, but conveniently, both can be controlled in the same way using natural insecticides, and control measures like neem oil or saponins from other plant juices in the garden. We’ll look at those natural controls for spider mites later in the article.
What are Spider Mites Attracted to?
The spider mite is most at home in dry conditions, which makes it a successful plumeria predator, especially on plants grown indoors.
Plumeria plants indoors are usually watered from their base, which keeps the soil dry but leaves wet. the dry leaves process copious amounts of chloraphyll from the roots, which feed the dry spider mite above.
By keeping soil watered over winter, you can often reduce the population as they struggle to cope with the wetter conditions without living green plumeria leaves or stems for feed on.
How to Identify Spider Mites on a Plumeria Plant?
Spider mites are common plumeria plant pests and, despite their size, are surprisingly easy to identify. The adult bugs are less than 1mm in size, have eight legs and spin webs, leading to noticeable imperfections on the upper leaf surface.
Symptoms suggesting the presence of spider mites are shoot tip dieback on the affected leaves, which can be recognized by an even browning or bronzing at the tip.
If you notice fallen leaves around the base of your plants in summer, this can often be a good indicator that something is wrong. Deciduous plants shouldn’t drop their leaves during the growing season, and this is usually a good sign of dehydration or pest damage. Spider mites in particular are known to hatch larvae at the base of leaves, where the chewed petioles and chewed leaves can often lead to leaves being completely detached from the main stem of the plant thanks to the immature pests.
Other symptoms may include leaf yellowing, a yellow strip down the midrib of leaves, slime trails (caused by trailing silk), and necrotic spots. all are signs of dehydration, with necrotic spots being a sign of chewed a chewed leaf petiole. Where moisture doesn’t reach the leaf at all.
Other plants affected in similar ways are avocado and citrus trees. Similar signs on these plants mean it’s time to take serious action.
They can often be mistaken for other insects as mealy bugs leave white secretions on plant surfaces, often mistakes for silk on the leaf. the difference between spider mites and other pests is that they are unique in the way they use their silk webbing.
Red Spider Mite
Red spider mites are tiny arachnids, with eight legs, and glowing red abdomens. The pupal stage have translucent white bodies.
They grow in four main stages:
- Red spider mite eggs are the most obvious sign of red spider mite on plumeria, as they are contained within a small clump of white webbing visible to the naked eye.
- Spider mite larvae are cream-white, six legged larvae, less than 0.2mm in size.
- Spider mite pupae are a similar cream-white, but with eight legs, and bright red eyes (there are two stages of pupae, but both look similar)
- The adult spider mite is around 0.5mm in size with a bright red abdomen that glows against green leaves. they are most noticeable by looking for clumps of silk webbing on the underside of leaves, and on the leaf petiole.
Sixspotted Spider Mite
Sixspotted spider mites are less immediately noticeable than their red cousins but are easy to spot when you know what you’re looking for.
Their larval, pupal and egg stages are almost identical to red mites, but their adult form is a more common predator of Plumeria.
Females mites are typically more abundant than male mites, as it is the female mites who climb the plant stem to feed and lay eggs on the healthy plant, laying eggs on the underside of the plumeria leaf, away from the risk of rain.
How Spider Mites Affect Plumeria Plants
Healthy plumeria begins to produce flower buds in the spring season, so as soon as the first generation of adult female mites emerges after overwintering in the soil, they begin feeding on the leaves and preparing to lay eggs on the early season plumeria growth.
Plumeria are tropical plants, so go dormant in our climate over winter, with not enough chlorophyll to sustain a healthy mite population. So every year, the mites overwinter and re-emerge to produce new generations, which dominate the plumeria leaves, starting to feed on the petioles and midribs of each leaf on the plant.
As the new generations form a new mite infestation, you will start to notice discoloring on the leaf surface. Usually, this is along the midrib of the leaf, which develops a yellow stripe due to dehydration, leading to leaf drop.
The most common result of severe spider mite infestation is blistered tissue and deformed leaves. As the infestation develops and mite damage builds up, the plant can be completely starved of water and eventually die.
Mite infestations build as new eggs hatch throughout the season, so if left unchecked can be visible from some distance, with silk threads hanging from the ends of leaves. Even now though, when your plumeria plant is completely overrun with a mite infestation, it is not too late, so let’s look at how to actually get rid of them.
How to Get Rid of Spider Mites on Plumeria Plants?
To effectively control mites, you need to take a measured and logical approach based on some trial and error, but always understand that the best way to treat spider mites is to understand their weaknesses.
Don’t just assume pesticides will get rid of the problem, most of the time they don’t work, and they harm beneficial pollinators.
Step one in tackling your spider mite problem is to get a water hose with a high-pressure spray and focus it on areas where the mites have gathered. Take particular care around affected leave and abnormally forming bloom clusters caused by the mites where they can hide.
The second step is to wait. If your problem was caught early, wetting the mites and knocking them into moist soil will stop them in their tracks. If they appear again after a few days, it’s time to think about natural control.
The best control measure for spider mite is soap. It might sound strange, but saponins, the naturally occurring compound that forms most dish soap, will starve them of water and oxygen by forming a coating around the tiny arachnids that they can’t escape from. Larger pollinators aren’t affected by it in small quantities, so just carefully spray it over the plants every few weeks while you have a noticeable mite infestation. Using dish soap works, but it’s best to use an organic chemical-free soap where possible (tip: If you happen to have Soapwort in the garden, you can boil fresh leaves to make a great chemical-free and effective control measure for spider mites).
Tips to Prevent Spider Mites
If your mite issue is limited to a few areas, it is best to just place badly infected leaves in trash bags as adding any fallen or affected leaf litter to the compost can create problems for other plants.
Spider mites thrive in areas with low humidity, dry soil, and poor air circulation. To prevent spider mites coming back, ensure your plant has good air circulation, continue watering plumeria regularly, and, crucially, mist your plants as often as possible. Humidity in the air can harm the spider mites before eggs hatch, and minimize the infestation.
Natural Spider Mite Predators
As for predatory control of spider mites, that’s a little more difficult. There are two natural predators you could introduce into your garden, Amblyseius mites and Phytoseiulus mites, but introducing these pests artificially could cause issues with other beneficial insects. the only naturally occurring common predators of spider mites are Thrips, but they are best avoided on plumeria plants, as they are a problem in themselves.
Recommended Products for Treating Spider Mites
There are a few really common ways to discourage bugs, and knowing the issues that can be caused by their natural enemies like Thrips, should hopefully steer you towards trying these organic pesticides rather than chemical control.
There are a number of different spray treatments, but as mentioned earlier, before doing any of this, use a high-pressure water hose to spray the host plant from all angles. this will dislodge most mites and make it easier to start a weekly routine. All you need is a spray bottle and some natural ingredients.
Neem oil is a great option for use with any mites, not just spider mites. It can have positive benefits on aphids too.
One criticism of neem oil is that it can be toxic to other animals, so it is not advised for use indoors in any homes with pets, and for outdoor use, it should be sprayed early in the morning directly onto affected leaves or the plant stem where mites are visible, to avoid accidentally spraying nearby pollinators.
Used responsibly this is probably the most reliable method to get rid of spider mites.
2) Rubbing Alcohol
I use alcohol on my house plants religiously (I have cats at home, and don’t like the risk attached to neem seed oil), and can say with certainty that this work on spider mites, aphids and pretty much everything else. The only problem with using alcohol is that it dries out the leaves unless you rinse it off afterwards, and takes ages to apply with cotton buds.
Azadirachtin is a chemical directly extracted from neem seeds and is supposedly more effective than neem. Personally, I don’t like to use it because it is a stronger a more general insecticide, meaning it is more likely to cause problems for other benefit insects, and its higher concentration means its effects continue to last once it has dried.
It can be bought online or in garden centres in low concentrations but should be used with caution.
Like Azadiractin, extreme caution should be used when using these indoors, and they should not be used near pets or other wildlife. Just because pesticides are organic does not make them non-toxic!
The Chrysanthemums are widely available in garden centres so you can buy your own, and dry the flower heads to make a tea, which will be equally effective.
5) Horticultural Oil
Light horticultural oil spray is a pesticide and should be used with caution. While ingredients differ between different oils, most contain a mix of neem, pyrethin and azadiractin as active ingredients. Sprayed directly onto existing leaves where there is an infestation clearly visible, it can be a good way to directly manage the problem but should be only be used when all other options have been exhausted.
To repeat my earlier warning, just because something is organic, does not make it non-toxic.
6) Dish Soap
Dish soap is a simple, cheap and effective control for mites, and many other parasitic insects. The soap works by connecting lipids and proteins in water, creating a surfactant (effectively creating an oxygen-proof film around the surface of the water). The resulting liquid stops oxygen from reaching anything that is coated in it, leading to suffocation and death.
Avoid spraying directly on other insects, and make sure to target the spray bottle at the mites directly.
7) Saponins (Soapwort Tea)
It works exactly the same way as dish soap, by suffocating the mite population on your plant stem and leaves, allowing the entire plant to be blasted with water quickly afterwards without worrying about other wildlife.
Because you can grow Soapwort in the garden even in cold climates, it’s a really useful plant, and if you ever have any Soapwort tea left over it actually makes a great alternative to shampoo, laundry detergent or dish soap too.
Alternatively, you can buy pre-made insecticidal soap if you don’t have the time to wait for Soapwort to reach maturity (which let’s face it, you don’t if you’ve already got visible guests on your plant).
Spider mites are easy to manage but can sneak up, often as a result of trying to control another problem. Many problems with plumeria are caused by over-watering, so the instinct to leave a plant alone to dry out can lead to dry soil, which will encourage a spider mite problem.
So long as you follow the rules above, it shouldn’t be difficult to manage plumeria spider mite with all organic controls.