DE works in two ways (maybe):
- It draws moisture out of anything it comes in contact with, including insects, which kills them. Once the DE is wet, it stops working.
- The second mode of action is a bit more questionable, there does not seem to be any clear consensus as to the veracity of this.....DE is made of microscopic diatoms, which have very sharp edges. This abrasiveness cuts up tiny insects and kills them. (notice the little scale at the bottom right that says 10 microns, that is about the thickness of a piece of paper. I'm going to come back to that in just a bit)
Ticks are very susceptible to changes in humidity, if it is too dry they die, so DE should work well on them. However, getting enough onto the tick to be effective is the challenge that I have not been able to master.
Spreading enough DE around the property that it might help is just not doable for me. It is especially not feasible as it would get washed into the ground during the first rain. Even without rain, it would absorb so much moisture from the ground itself that it would be rendered useless within minutes. Once it is really wet, it clumps up and even its abrasiveness is rendered useless.
I have used DE to dust the animals directly as well as in chicken coops and in the garden. It works great for treating lice and mites on donkeys, horses, cattle, chickens, etc. I did not see that it helped keep ticks or flies off.
The trouble/blessing with it is that it is such a fine powder that it settles down into the hair next to the skin. That may be why it works so well for lice and mites, but ticks just crawl over the top of it. Also, I find 99% of the ticks attached under the chin, between the front legs and in the inner thighs. The DE just won't stay there. I even tried putting it into a solution and spraying it on, but it had no noticeable effect that way. I have found live ticks attached right through a layer of DE.
A couple of the the things I do not like about using DE on the animals is that it is a definite irritant to eyes and lungs and it really dries out the skin. That last can be a good thing for the donkeys when it is extremely humid as they are meant for a dry climate and are prone to fungal infections, but used routinely, it is too much.
If anyone more clever than me comes up with a successful way of using DE to control ticks, please do let me know. I would appreciate it.
Since I get asked about feeding DE, using it as a wormer or feed-thru fly control at least 6 or 8 times a year and we're on the subject....
When DE first started gaining popularity 12-15(?) years ago, we were all set to jump on the band wagon. It sounded like the greatest thing since sliced bread - a natural, organic pesticide, wormer, miracle cure that parasites could never develop a resistance to. And, for the external parasites I already mentioned, it is all that.
Since that time, I've learned a lot more about DE and the entire premise of using it to treat internal parasites now seems ridiculously faulty to me. The first mode of action, as a desiccant, becomes moot as soon as it hits the stomach full of fluid. As for the second mode of action...If it actually DOES work that way, I just can't see how it would be safe to feed in doses large enough to actually kill parasites. Maybe its because of my job as a histotech, but that idea just scares me. and here's why:
The photo below was taken through a microscope. It is a piece of normal small intestine
Those finger-like projections are where 90% of nutrient absorption takes place and they line the entire length of the small intestine. This tissue section is cut at 5 microns thick (remember the scale in the first photo?), to put that into perspective, a red blood cell averages about 7 microns. Lining the outer edges of those fingers are super tiny cilia that are so small they can't be seen here. If you look REALLY close at the top of this photo, you will see that the outer edge of fingers appear to have a faint, pink fuzz - that is called the brush boarder and is made of those tiny cilia. They are like little Velcro "hairs" that reach out and "grab" individual nutrients.
Remember those big, sharp diatoms in the first photo? If DE really is that abrasive, what do you suppose they might do to these tiny, delicate, crucial structures when fed in sufficient quantity to "shred" worms? The way I see it, if it is safe to feed than it is not going to kill worms through sheer abrasion. If it does kill worms that way, how can it be safe to feed?
DE is considered safe as a food additive and is used as an anti-caking agent in feeds. However, it is generally used in very small amounts in feeds that are themselves supposed to be fed in small amounts. A large enough quantity of DE to kill parasites through sheer abrasion while inside the GI tract....nope that just doesn't make sense to me.
I personally know several horses who were routinely fed DE to control worms. They all suffered for it and at least two youngsters nearly died of anemia caused by extremely heavy parasitism. To my eye, horses who have been fed "therapeutic" doses of DE for a long time have an unthrifty look to them. They often have diarrhea and their hair coats look long and dull. Whether from worms or the DE itself, I couldn't say.
My opinion, for what it's worth to you....Use DE to dust for lice. Use it to dust the bedding litter in chicken coops to kill mites. Use it in the garden to kill aphids and slugs, but don't use it to kill worms. If the propaganda gets to be too much and you absolutely MUST try it, do regular fecal egg counts and if your critter starts acting listless and lethargic, stop feeding it and call your vet ASAP.