A few days later: I notice that a few other plants are having a LOT of dropped flowers. Weird, I think. I do a bit of research, I decide I'm probably overwatering them, so I cut back on the water a bit.
A week later: Now it's concerning. I see that the new growth on many of my chillis, about 70% of them, is black and dropping off. Shaking almost any plant causes a torrent of flower drop. Oh, this is not right. Not right at all.
First thing that occurs to me at this point is "pests". But I look over them, no webs for spider mites, no mealy bug, not a lot of anything.
But the new growth is crispy deformed and black, and while some chillis like the thai super and apache (the dwarf ones notably) are managing to still struggle through, the Jalapeno, the hot wax and cayenne, scotch bonnet, habanero, the list goes on. All struggling.
I begin to doubt my chilli growing abilities. What have I done?
If this sounds familiar - then get yourself a magnifying glass, a good strong light source, and a pair of good eyes. We're going mite hunting!
What are you looking for? Something smaller than a full stop (that's a period to you Americans), on the underside of the leaf. That's right, smaller than this ---> .
They appear to be white, they're like a grain of white pepper, they're about 0.2mm, and they move pretty fast (can walk width of a leaf in about 10 seconds kind of fast). Many people say they're not visible to the naked eye but they most certainly are, although all you can see is a tiny white bit of moving dandruff.
Put your magnifying glass up against them and you really dont get much detail.
The important bit to note is that part of identifying you have them is seeing them moving. Stationary white dots are probably not broad mite, they almost always are on the move in my experience.
Here's a youtube video I managed to get of them - this was with a usb microscope. I'm not entirely sure of the magnification I was using but it would be around 100x at a guess. Enjoy.
http://www.youtube.com/watch?v=gXoXMNwcF-w
As you can see from the title of the video, I had not identified them at this point.
So - from the title, I say I won. Well, it's too early to say, but I did eradicate them around a month ago and have yet to see any signs, and from what I can see online, that's actually the best result you can really expect with these microscopic monsters.
So - what's the deal? Well, I did not want to use any pesticides or chemicals. Firstly, because I studied a lot of forums, a lot of websites, a lot of commercial products, and I didn't want that stuff on my peppers. I'd rather throw them all away, get out the bleach, do a once over, and wait until next year. Which to be honest, I thought that's what I'd have to do. Maybe it still is, but we'll see.
So, lets go over what we know about these pests, and gather our options:
1. They are tiny
2. Because of the unique way they attack plants, especially capsicum it seems, they really do kill the plant off, or at least, bring it to its knees and make it incapable of producing any fruit or growth, which is pretty much dead in my eyes.
3. You only need a few to get this extent of damage. I've read that just five insects can cause symptoms to begin.
4. They breed pretty fast, similar to spider mites.
5. They are territorial, so while you will see them on new growth, they are always fairly spread out, you don't get bunches of them, you get a few on every leaf in my experience. Even on older growth if they so choose.
6. They are always on the underside of the leaf in my experience. Usually toward the central vein.
7. They are hard to kill with pesticides.
8. Commercial growers use miticide in combination with "good" mites, predatory mites that have been shown in studies to really gobble up the broad mites. There is very compelling evidence that predatory mites, amblyseius cucumeris especially, can bring an infestation into check fast.
9. They are intolerant to high temperatures, above 40C, in all lifecycle stages
Point 9, a little known fact actually, was the key. I found some obscure references to using temperature against them. I found some had tried raising temperature in air, but had failed. But there really was no information other than a brief paragraph or so online about cyclamen mites (closely related) and hot water.
So - how was this going to work?
Well here's what I did.
- dispose of any badly infested or non crucial plants. Bring the odds in your favour.
- prune all remaining fruit off the plants, edible or otherwise, you want the plant to concentrate on recovery after what you're about to do to it, so remove all the fruits.
- cover the pots WELL with plastic bags. You will be surprised just how much soil can leak out of even a securely bagged up pot, so be prepared for a muddy mess.
- if you have any large plants > 3ft or so, either trim them down or bin those plants, because submersion in entirety is really really important.
- Get yourself some weights. Not concrete or brick, stuff like a few plant trays. But make sure you have sterilised it first if you think there might be mites on it - boiling water would work I guess.
- You need need need an accurate thermometer. I used an infra red digital gun thermometer, they're cheap enough now that I would recommend anyone gets one, they have so many uses.
- You also need a stopwatch or timer.
All ready? Take them to the bathroom. And now's the time to be thorough. Remember, if just a couple of mites survive, you're going to have to do this all over again. And trust me, you won't want to do it all over again.
Run the bath to as deep as you can and you need the water to be 43 degrees C. Not 44, not 42. You need exactly 43. Now, don't worry about maintaining that temperature once the plants are in, you have a bath full of water, it will stay hot for a while, trust me. But bear in mind the surface will be cooler than the bulk of the water, so swirl it with a stick. Use your hands if you like but I found 43C to be quite uncomfortable.
Once you're at 43C - put your plants in and set the timer/stopwatch. You need 15 minutes. No more or less.
Now is also a good time to wipe your windowsill, window surfaces and/or spray them with dettol or other bleach solutions. I really don't know whether broad mites hang out away from plants, but it's prudent to take a few minutes to clean up, it can't hurt.
When 15 minutes is up remove the plants, stand them up, and don't be surprised if they look like boiled cabbage.
Now be warned. Your chilli plants won't much like 43C either. All my plants lost their leaves. All of the leaves dropped off within 24 hours of the "dunking". I thought that was it, I'd killed them. But alas, they all survived, new growth came in very soon, within a week, and that new growth almost invariably came with flowers!
So here we are. Let's hope they don't come back in a hurry. I will of course update this later on.
UPDATE: 19 Aug 2013 - Almost 2 months have passed and no sign yet of a return of the mites. Growth and fruiting are good on some plants, other plants are still struggling. The plants I abandoned into the garden and did not treat are NOT doing well, and have no flowers or fruit, so the treatment option wins so far.
2ND UPDATE: 25 Sept 2013 - Another month and almost the end of the season, and not a mite in sight. A reasonable harvest too considering how many plants I had to destroy. I think we can safely say this was a success, and I highly recommend this as a treatment.
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