Mites: Death to all spider mites. This is war.
Ok now that we have looked at the most common mite; two-spotted spider mite a little bit closer it’s time for the fun part.
Let’s nuke em!
There are 3 different natural methods I am going to go over here which are all fairly affordable.
Before we begin though I have one PSA announcement. If you have some leaves that are covered in webbing I would highly recommend bagging them and throwing them out as it will be almost impossible to cure those. If your entire plant is coated in webbing it may be time to do a last ditch propagation attempt to save it (thoroughly cleaning any propagation plant material and tools in the process) or maybe, this is the end of the line for it :-( Once spider mite levels get that high often the damage to the plant is irreparable.
Ok here we go!
1). Water
Yeah I know that seems pretty blahze’ for the first item on the list but hear me out. If you have access to a garden hose or faucet that you can turn onto blast mode this is the way to go. It is as simple as bringing your plants into the sink or tub and giving them a good shower. Make sure there is some pressure in the water coming out to blast off any eggs and adults that are holding onto the leaf. This is a fantastic way to break the reproduction cycle and literally knock down the populations to a much more manageable size. Make sure you flip over the leaves and wash the underside since that is where the majority of spider mites are. This method is essentially free and easy to do but does require some commitment and repetition since odds are you won’t wash every single mite off in the first shower.
2). Horticultural oil + soap
At this point we all know neem oil but there are several other great oils out there that do a great job on mites. They all do one thing - suffocate. It is not guaranteed to kill 100% though as the coverage isn’t foolproof. Your best bet would be to hose them off (bonus if you mix a TINY amount of Dawn soap with that) then spray them down with some diluted oil. Remember to focus on hitting the undersides of the leaves. Do NOT use oil from your kitchen pantry - not all oils are created the same and the ones typically used for cooking can burn a plant. Horticultural oils are a much finer grade oil that will allow the plant to breath and minimize any risk of phytotoxicity (aka burn or damage to your plant). Only apply oil when the plant will not get direct sun i.e. rainy days or at dusk/night.
3). Predatory Mites - Phytoseiulus persimilis
OK FOLKS! THIS IS THE ONE!
No mess/cleanup - check!
No moving plants - check!
No multiple treatments - check!
Safe and effective - Double check!
Hands down this is my preferred method of controlling and eliminating spider mites from my plants, entirely. Forever. I apologize if I put in too many exclamation points or caps in this last section but I am just so excited to talk about this! Beneficials and biological control are my jam and I hope that more people start to accept and use this method in the future. It would save us all a whole lot of trips to the kitchen sink or bathtub.
Ok back to persimilis.
Phytoseiulus persimilis is a specialized predator of spider mites. Basically it only eats web spinning mites but it eats them with a voracity! Our most common mite that we ID’d earlier - the two-spotted spider mite is at the top of their food preference list.
An adult persimilis can eat 5-20 tssm (eggs or adults) per day! Their goal in life is to seek and destroy tssm.
Although they do eat all stages they tend to have an affinity for the egg stage as the nutrients in the eggs help persimilis with reproduction. They are very easy to tell apart from tssm; they are a bright orange color with two long front legs, a tear dropped shaped body and compared to tssm they are fast. Even their eggs are easily distinguishable from tssm eggs. Persimilis eggs are larger and have an oval shape to them whereas tssm eggs are perfectly round and small.
Pictured here are two persimilis hunting for a spider mite snack. They are the bright orange mites with long thin legs.
The persimilis in the middle of this photo has grabbed onto a spider mite and is busy sucking out its contents.
Nature is hardcore.
Get ‘em boys (and girls)!
Persimilis are very effective at finding tssm and although they are essentially blind they use kairomones (aka mite odors) to find their prey and if they encounter webbing they intensify their efforts. These mites can travel up to 10 feet in search of prey but often if there is food readily available they won’t disperse that far. If there is no food present they will eat each other - fun fact the females will eat the young males first…. you could say that persimilis ladies are “man-eaters”… Ha.. Ha…
Back to business.
As I have said before, persimilis will eat two-spotted spider mites to literal extinction. Don’t believe me? Let’s take a look at this graph from Laing 1968:
In a nutshell this graph shows that at 68.5 F persimilis:
Live longer (29.6 days vs 17.8 days)
Lay more eggs
Bigger female to male ratio 4:1 ratio vs 3:1
The science speaks for itself and I have seen it work time and time again.
You might be thinking that this sounds way too good to be true. It is not! It is just biology at it’s finest. However, there are some things to consider when using persimilis to get rid of your tssm:
They need humidity. The adults will survive at lower humidity but their eggs will shrivel at humidity’s lower than 50%. The higher your temperature, the more important it is to have higher humidity. In a house, your ideal humidity is 30-50% which can be difficult if you are trying to grow tropical plants or use persimilis. If you have your plants growing in a humid space then this won’t be a problem but if you have your plants growing in low humidity persimilis may not work for you. Don’t know the humidity in your house - check out my all time favorite temperature and humidity tracker - SensorPush.
Be sure you have tssm and not some other mite. As I mentioned before, persimilis pretty much only go after web spinning mites in the subfamily Tetranychinae (two-spotted spider mite, carmine red mite, pacific mite). If you have a different mite these guys won’t work. Think you have tssm? Check out my previous blog post: “Mites: How to identify them and a little biology” for help identifying these.
Any recent miticide applications may kill persimilis. No I am not talking about neem oil - although keep in mind if you do use neem oil after putting out persimilis you will kill them too. Horticultural oil is not selective in what it targets. It will suffocate anything and everything it lands on.
Ok, there you have it folks! These are my tried and tested ways to get rid of spider mites. Interested in getting some persimilis but not sure where to go or what to do with them when you get them? Stay tuned for the next post on where to get these guys and how to use them!