Diatomaceous Earth--wet foliage first?

[peebee]

I'm thinking of using food grade diatomaceous earth for spider mites. Question: since it is a powder, do you wet the plant first so that it sticks? Or will it stick just fine on a dry plant? Thanks.

[Gerardo]

You can make a slurry, 2-3 tbsp into 1 gallon of liquid, and apply with a regular sprayer. Once dried, it leaves everything covered in a white film. The diatoms are like punji sticks to the insects.

Spreading it around the mulch as a powder can work too.

If you add some Neem Oil and a few drops of dish soap it becomes a real killer mix.

Good luck!

[peebee]

Thanks Gerardo, but I was hoping I wouldn't have to spray. I'm already spraying Neem and not enjoying it. I've read that some people put the powder in a condiment bottle (like ketchup) and squeezing it out, that's why I thought if I did that, DE might stick better if the leaves were wet first. What do you think of that?

[b54red]

It will be easier to make a slurry of DE and water with some dish washing soap. I use at least a half cup of DE to a gallon of water and mix it in a separate container shaking it very well then strain it into my sprayer then add the soap. I use 2 TBS of Dawn dish washing liquid to a gallon of mix. I also add Permethrin for spider mites.

The soap helps maintain the slurry but still it is best to shake the spray tank several times as you spray. The soap also helps penetrate the webbing of spider mites. The Permethrin helps kill off the adults and the DE helps keep down the new ones hatching. This mix is the most effective thing I have found for spider mites.

If you insist on dusting then it would be better to get a good duster and adjust the nozzle so it points up so you can get more dust on the bottoms of the leaves where the spider mites are mostly located.

If spider mites are bad then you don't have long to get them under control. I had a bad infestation a few weeks ago when it was unusually hot and dry here and I was unable to treat my plants for two weeks after first noticing them. In that two weeks they completely ruined quite a few of my plants covering them from top to bottom and sucking the life out of them. It never pays to wait when spider mites are concerned; but I was unable to act due to health reasons. I finally got my spray done a few days ago and I know it was too late for some of my plants but I'm hoping the others will recover. Since spraying all my plants have a ghostly appearance thanks to the dried DE coating them.

Bill

[jillian]

Originally Posted by peebee

Thanks Gerardo, but I was hoping I wouldn't have to spray. I'm already spraying Neem and not enjoying it. I've read that some people put the powder in a condiment bottle (like ketchup) and squeezing it out, that's why I thought if I did that, DE might stick better if the leaves were wet first. What do you think of that?

It will stick better if the leaves are a little damp. Early morning dew is perfect. Cut the tip off of the condiment bottle so it will come out easier. You will get the feel of it. You will not get the coverage as in mixing with water and spraying, but it works for me.

[Gerardo]

As long as you get it on there, it'll do the job.

[fonseca]

I use a squeeze bottle for DE. The tip is cut off halfway, and I have a piece of hardware cloth pushed an inch into the bottle to prevent it from clumping. It works, but my hands don't care for it after dusting the whole garden. I use a flour sifter to quickly apply a layer over container mulch, which keeps slugs, ants and earwigs from taking up residence.

I apply dry and my plants get a good coating, but if the plants are wet you definitely get more adhesion. The trick is to aerosolize the DE so you get little clouds of it moving through the foliage. I constantly shake the bottle when applying. I haven't had to treat any tomatoes this year, only brassicas and greens. My cucumbers could use it, but I don't want to kill bees.

I use feed grade DE with bentonite clay. Not sure how that would do in a pressure sprayer.

[b54red]

Just spent 4 hours in the garden watering with TTF and checking my plants. I saw no new spider mite activity nor any old spider mites so a couple of days without any significant rain and the spray mix I used looks to have solved my mite problem. Of course they could come back if the DE gets washed off by a heavy rain but I won't wait to act if they do. Surprisingly plants that even had mites on all the new growth are now starting to put out clean new growth so I may wait and see how they do instead of pulling them. We still have a lot of season left down here and I still have some seedlings left to plant.

Bill

[peebee]

Thanks everyone. I could not wait any longer, so instead of ordering online I called the local hydroponics store (they have everything!) and yup they had food grade DE, as did a pet store nearby but they were more $$.
Got 2 lbs plus a good 1 gal. pump sprayer for $8 ea, no tax not bad. I first sprayed just neem, dr bronners soap and water then used a condiment squeeze bottle for the DE. Not a pretty sight when I was done . The DE did not go on evenly and it looked like I graffiti-ed my garden in white . So for the remaining plants, I sprayed with the neem, then mixed water into the squeeze bottle, shook well and finished with that slurry. That looked much better. I will try the advice given here and just add the DE to the neem mixture next week although I am afraid this will clog up the sprayer.
Hope I can get at least 4 more weeks of tomatoes from this treatment. The mites were not too bad yet; yes I know sometimes they can destroy your entire crop seemingly overnight. Gotta do the office garden next week if I can spare the time, sigh...

[BigVanVader]

I use what Bill said but my extension agent recommended 2 cups per gallon of water and I havent had any issues spraying it. I like to use warm water and add a little Neem oil as well.

[peebee]

BVV, what kind of sprayer do you have? I can't imagine using 2 cups of DE per gallon, seems like a lot and it would become quite an expensive spray if you were to do this every 2 weeks. About how many plants do you figure you can spray with a gallon?

[BigVanVader]

I have a typical 4 gallon backpack sprayer. I usually mix 4 gallons at a time and that sprays everything I have. I might try less since y'all get good coverage with it.

[b54red]

I have used over a cup of DE to the gallon but found myself having to sometimes open up my spray valve and clear it with a larger stream and found that a finer mist was not practical because of how often it started to clog. I also found that I got a heavy buildup of DE in the hose from the sprayer to the wand that took quite a while to wash out. I found that mixing the DE and some of the water in a separate jug, shaking it well then straining it into the sprayer tank helped keep clogging to a minimum.

If the mites are really bad like they were the last time I sprayed I will go slightly above the 2/3rds cup to the gallon and the coverage is better but it may take a bit longer to apply. I use an SP2 4 gallon backpack sprayer that builds up a lot of spray pressure and ordinarily will spray a super fine mist at a high volume; but when using a heavy concentration of DE I need to use a heavier mist in order not to start clogging the nozzle. The food grade DE mixes quite well in water and holds in suspension longer than you would think but it will eventually sink. I think the soap helps hold it in suspension longer but I try to shake my spray tank as much as possible when working to keep it suspended better. I have no idea how much can actually be used and still spray but I get good coverage with between 1/2 to 3/4 cup of DE to the gallon so why invite sprayer problems.

I have found the mix to be very effective at killing almost any insects including caterpillars which have also disappeared. My stinkbugs and leaf footed bugs are also gone but with so much season left they may reappear before the season is over along with the dreaded spider mite. I may do a follow up spray soon of just DE and water on the new growth just to assure myself that new spider mites don't attack that part of the plant that is unprotected by DE.

Bill