Spider Mites

I won’t pretend to be an expert on these awful little critters but here is some knowledge I’ve researched and some measures I’ve taken for my own plants in the nursery to combat spider mites.

Why worry about Spider Mites? What can they do to plants? Spider mites suck out the nutrients from plants so they can do real damage if they are numerous enough. If not caught in time you could lose your plants and given some indoor plants are quite delicate (and expensive) it could cost you.

Spider mites thrive in environments where the temperature is higher and humidity lower.

The eggs hatch in about 3 days, producing larvae that have six legs and are colourless. From these, nymphs develop, which have eight legs; they moult once and within a few days become adult. The adults are about 0.5 mm long, with each female laying about 100 eggs.

Under tropical conditions the life cycle takes only 7-10 days depending on temperatures. Populations develop rapidly, especially during periods of drought when damage can be considerable. The adults live for 2-4 weeks.

Firstly, how to identify them. The mites are hard to see with the naked eye so best to look out for some telltale signs:

Webbing – very very fine webbing that is smaller than a spider’s web and usually found on the underside of leaves.

Spider mite webbing

Spotty damage on leaves – You will probably find yellowing patches with telltale spots on the top of the leaves.

Stippling on leaves is an early sign of spider mites

You’ve found some, now what? Firstly; quarantine the plants that are infected from the rest of your plants – spider mites can jump from plant to plant and spread fast. Next; wipe or hose off the leaves (depending on their fragility). You will be wiping off most of the spider mites and their eggs. You’ll need to wipe the leaves every few days for a couple of weeks as the egg life cycle is three days.

Ways to keep them under control:

  1. Release Natural Predators – I have ordered predatory mites a couple of times to get on top of mites and so far it seems to work. I ordered from Bugs for Bugs and they have info on their website to help you choose what would be best. You can still use a few sprays with these but it’s not recommended as most kill all insects.
  2. Sprays – there are many commercial sprays that can kill mites. Just find your local nursery and ask. If you want to routinely spray as a preventative it’s best to use a few different active ingredients in rotation so the mites don’t build up immunity too fast. Please bear in mind that these sprays usually kill ALL insects that they come into contact with, good and bad. You will be likely wiping out all of the beneficial insects that exist in the little ecosystem so will be more reliant on the sprays in the future. I would personally use these as a last resort, especially as releasing beneficial insects cannot happen with most sprays.
  3. Wettable sulfur – a combination fungicide/miticide which can be purchased at most good nurseries. Follow the instructions on the packet. Check beforehand if they can be used in conjunction with releasing predators as I am not sure.
  4. Home made chilli or garlic soap spray – recipes are available on the internet. I would use these with caution as too much oil on a plant can clog pores and suffocate the plant a little.

References: Pictures in this article have been found at the following locations. No product recommendations are sponsored – I am not making any money for recommending.

https://www.pestnet.org/fact_sheets/spider_mites_024.htm
https://www.dragonfli.co.uk/blogs/news/which-predators-to-use-for-the-control-of-spider-mite-and-how-to-use-them
https://extension.entm.purdue.edu/pestcrop/2007/issue17/index.html
https://cropwatch.unl.edu/2016/identifying-spider-mite-damage-species-responsible

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