How do you clean your greenhouse?

My greenhouse is infested with spider mites. Sadly, it took me a long time for me to identify what was causing the stippling on some of my plants that I've overwintered in the greenhouse.  I usually don't bother with treating any of my plants for insects. My experience is that my garden insect issues generally go away with time and don't cause that much damage anyways, so I have relied on beneficials and the changing seasosns instead.  However, there are no beneficials in my greenhouse and not much of a change of seasons either.

Now spring seed starting season is in full swing, and I to need get rid of the mites ... and the newly arrived aphids that showed up on my chives, of all things!  I've searched online and asked many friends about how to clean a greenhouse in a way that kills insect eggs. I couldn't really find any good answers. We ended up power washing the greenhouse interior down, then we washed it with soap and water, and then we sprayed it with diluted peppermint oil. I am now checking my greenhouse plants daily and spraying the infected ones still remaining in the greenhouse with insecticidal soap daily until the situation is clearly under control. (The chives and anything else that can tolerate the cool weather are outside now.) I am planning to put some flowers in the greenhouse this summer in hopes of attracting beneficial insects. I may end up ordering some P. mites, too, if the mites persist.

That's what we've done and my plan going forward. But I figured you all might very well have some better ways to handle this issue organically. What do you use?

Thanks!

Hi Jen,
I don't know about spider mites, but having chickens in your greenhouse overwinter can help break some pest and disease cycles and add fertility to the soil as well.

I have heard that the best way to get rid of spider mites is with alcohol.

That sounds more like a individual plant treatment.

If I had your problem, I would take everything possible out of the greenhouse.

I would then spray the whole greenhouse with a soap solution.

See said, You want to dissolve 20 gram soap in 1 liter hot water and let it cool down, then you mix 30 ml Spirits into it and try carefully if your plant can take it.

https://permies.com/t/25083/permaculture-house-plants/spider-mites-die-Organic-solutions#1629828

A second spray when the greenhouse is dry with a vinegar solution mixed 50/50 vinegar to water..

A third treatment with a baking soda treatment.

https://permies.com/t/93537/toxic-Fungicide#1423936

These treatments will probably get rid of all nasties that might be there.

Then treat everything that goes back into the greenhouse.

Maybe any plant that are left can be treated individually.

Jen,

I've used tobacco "tea" on mites and other such critters in the past in the garden and several times with house plants.


The soaps or oils (maybe NEEM ?) may work for the eggs.


I've never had a greenhouse, just cold frames for spring and mini plastic tunnels for fall.

I think the degree to which a natural balance will return to your greenhouse will depend on it's size. Smaller enclosures have less chance to find balance. I had spidermite in my tunnel here in the first few years. I couldn't grow courgettes or aubergines, they even damaged the grape vine somewhat. I did get some Amblyseius californicus predator mites in the hope that they would help deal with them, but I don't actually know if it helped. I think increasing mulch and general mess gave more habitat for predators, and improving the watering increased the humidity in the tunnel which helped as the spider mite prefer it dry. After a few years I no longer noticed an issue with spider mite.