Spider mites

grizzmanJanuary 23, 2014

So I've recently had my first encounter with spider mites and thought I'd share a little as well as inquire of the best way to get rid of them. Ironically, I didn't get them on outdoor plants. They appeared on some mint I took to work to keep inside for winter.
How do I know what they are? The first clue is the bronzing of the leaves. I also noticed a bit of webbing between two leaves.
Everyone always say you need a magnifying glass to tell for certain that you have them but I found an easier way. Simply rub your fingers across a suspect leaf. If they're there, you'll have little sred treaks of squished bug on your fingers.
Also, online, everyone suggests mint extract as a decent natural pesticide. Well I don't think it will work on spider mites. That is what they're eating!
So anyway, how do you control them?
I've been rubbing my fingers over all the suspect leaves with plenty of squish satisfaction. I've also been trying a garlic water spray on both sides of the leaves. (another observation: the scent of mint ALWAYS overpowers the garlic scent. . . who knew) What else can I do? I was considering cutting the plant down to the soil and letting new shoots develop and trying to keep them clean. Do y'all have any other suggestions?

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It's hard to find many of the good old organophosphate pesticides any more. A lot of them have been banned for retail sales.

A Hot Shot No Pest Strip will kill spider mites easily. It's dichlorvous, which is an organophosphate. It also says "not for use in living spaces" on the package. You don't want to breathe the smell it puts off. It will kill mites right away, but then their eggs will keep hatching for the next month or maybe longer.

Alternatively, you can buy predator mites, and they are a lot of fun to watch under a magnifying glass as they eat your spider mites. But the eggs of the spider mites will outlast the predator mites, so I don't think they are a permanent cure.

Here is a link that might be useful: Pic of a Hot Shot No Pest Strip

This post was edited by Cole_Robbie on Thu, Jan 23, 14 at 19:25

    Bookmark   January 23, 2014 at 7:23PM
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PupillaCharites(FL 9a)

I second the predatory mites from reading, but that wasn't something I was prepared to administer. The two-spotted spider mite is a known principal pest for strawberries in Florida, and I wanted to be prepared.

So far I've not needed to apply anything, but I spent a lot of time researching what to do when a few started appearing in the warmer fall. In the end I decided on buying an ultra-refined parrafinic mineral oil. Other horticultural oils didn't come up as very effective except that type in particular.

The old brand that was mentioned as used successfully, was Sunspray, but I couldn't find it being manufacturered any more. After looking around a bit I was satisfied that a good substitute brand/quality was Bonide's product. The bonide product comes in two forms. The regular one at garden centers is usually highly diluted into an emulsion and ready to spray. Obviously the amount of oil in the RTU spray is very little making it an expensive 98% water bottle product which I would like to have more around since it is not really toxic (but it can suffocate you to a horrific death easily if you nebulize or breathe the liquid concentrated into your lung, like has happened to people who get high sniffing volatile petrocarbon solvents).

And suffocate is what it it is claimed to do exceptionally well to the spider mites. The dilution ratio is very very large and I got a great deal from Ace Hardware $12.99 online, shipped to pickup at the store for free. The product I got is the concentrated one which I will never run out of, a quart and it is called Bonide All Seasons Horticultural and Dormant Spray oil concentrated . I have yet to use it, but I'm pleased to have it in the toolbox as anything else there, besides the preditory mites were a little too involved for my small hydro-pad with hungry lizards and huddling mini tree frogs now that it is cold which form the natural front line. The pesticides that work all seem to be quite toxic chemically for my taste so I felt this was the best compromise when I looked over what to do.

Sorry not to have results to share, and I really hope I don't have to cross that bridge! But it's here when I need it. The literature seems to suggest using 2% in Spring, maybe every 10 days if necessary, spraying after dark when the mites come out, and under the leaves. 3% if I want to go after the eggs effectively. Unlike other chemical controls, this one is the mildest in the sense no "waiting period" seems to be required, though I would definitely give it a good washing.

Bonide says it is ok for organic gardening. This oil is an alkane-oil and the ultra-refining "superior grade" refers to distillation, removal of sulfur compounds, the removal of aromatic hydrocarbons (non-alkane) oils, which is thought to leave a product that is non-carcinogenic according to regulators.

Bonide's MSDS says practically non toxic if ingested, however potentially fatal if drawn into lung where it will smother. This refers to a large amout of the concentrate compared to the application rate. It also says if ingested to drink water to dilute. I think that's asking to be sued in a staged tort case - I wouldn't drink water as that is more likely to cause vomiting and getting it into the lung. Minor point, but it indicates a bit about the MSDS quality.

This post was edited by PupillaCharites on Fri, Jan 24, 14 at 2:19

    Bookmark   January 23, 2014 at 10:37PM
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So is the bonide the same stuff (or similar product) that makes the apples shiny in the grocery store?

    Bookmark   January 24, 2014 at 7:20AM
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PupillaCharites(FL 9a)

No, it's petroleum based and the ones in the grocery stores are solid, specifically FDA food grade shellac derived frequently from trails excreted by bugs, or sometimes from palm leaves, also solid. Both are dissolved in alcohol to apply which then dries and leaves the white film residue which is then polished. This is actually a lighter liquid oil at room temperature. It mixes directly in water due to a soapy emulsifying additive,I'm thinking.

This post was edited by PupillaCharites on Fri, Jan 24, 14 at 10:01

    Bookmark   January 24, 2014 at 9:56AM
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Dipping the plant in soapy water will smother living mites for next to zero cost. But you're supposed to go back after the soapy water dries and spray off the soap residue with plain water, because the soap residue is not good for leaves long-term. And like I said, the mite eggs start hatching out again right away. So it's a big pain, and it just manages more than eliminates them.

From what I read, the mites can also be smothered with high levels of CO2, just like any oxygen-breathing creature. But I think the eggs live through that, too.

    Bookmark   January 24, 2014 at 1:48PM
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PupillaCharites(FL 9a)

The reason for the long term problem with the soap is because any of the "free" soap we might use from our household is almost always containing all kinds of additives that are bad for plants.

If you were to go the soap route, better to just buy a special insecticidal soap, they are very cheap, even a little less than the ultra refined oil. They are fatty acid based soaps, except instead of using lye like pioneers did to make soap, potassium hydroxide is used to saponify to keep the soap sodium-free for the health of the plants. Dishwashing liquid or detergents are specifically no-no's because in addition to the additives, they are usually mostly stronger sodium anionic surfactants, not a "traditional soap" which are weaker carboxyl terminated which is what is used principally in nature. So the soaps don't smother, they disrupt insects and plants' metabolism by "popping" cell membranes. If you happen to have a non-ionic soap around, that would be the best. As a matter of fact I recall it is the 'secret' ingredient to slip extra nutrients into roots of "Wet Betty" LOL.

Soaps actually work differently than horticultural ultrarefined (superior) oils. They don't smother as much as as get ingested and in a one time event destabilize the cell membranes, like what happens when you add a soap to water with a film of oil floating on top.

Some people have used lighter vegetable oils, typically Canola, continuously shaken up in a bottle at 2% but not many people feel it is worth doing. That is another cheap and easily available control in a pinch, like soap.

That's the basic difference between the ultra refined oil and a traditional oil. It forms a microscopic emulsion instead of a droplet laden mixture which wets the entire leaf surface, and that is why it actually works more effectively on the eggs too. The most effective way to apply is actually first lightly spraying the plant with plain water and then immediately spraying the fine oil. It then forms a continuous barrier which later is a barely perceptible silky sheen they is usually no problem or even nice. That silky sheen provides a great degree of protection against the diseases that inevitably enter plants from the pest injury sites (unlike soap residue which can be harsh and dry leaves), and for the same reason is considered an effective antifungal too. They don't taste soapy either and there are no warnings on having to wash the oils off, whether for plant health or to eat, so they can be applied frequently without worries. But I just would wash before eating anyway!

In the end it depends on how serious the situation is and how big of a plot you have. If they are only a few houseplants maybe you had the right idea just squishing them.

    Bookmark   January 24, 2014 at 3:38PM
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slowjane CA/ Sunset 21

has anyone used orange oil to kill spider mites? i got some to treat a tree that had termites...

my snap peas are rife with mites, i think partly due to our unseasonally hot and dry weather here in socal....

    Bookmark   January 24, 2014 at 3:53PM
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PupillaCharites(FL 9a)

There are some references you can Google showing that menthol (mint active) is more effective than d-limonene (orange oil active), and they are infesting his mint .. so it's worth a try depending on how your product is formulated (emulsified) it is generally marketed for on-contact killing of ants and termites.

    Bookmark   January 24, 2014 at 5:08PM
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I had spider mites real bad one time and the only thing that got rid of them was flora mite. Get it on ebay in a little small bottle that will last a year which was about how long it took to finally be done with them. That was also bombing once a week with permethrin. Yikes, makes me shiver just thinking about them. This was the two spotted mite. Good luck.

    Bookmark   January 29, 2014 at 7:17PM
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