Pros: Effective eco-safe pesticide kills most crawling bugs.
Cons: Non selective. May need to reapply after rain.
As anyone who has read my series on building and equipping greenhouses will know, I recently started growing fruits and vegetables organically in containers. Last year, I got lucky. Most of the bugs in my garden were so stunned to see a human in their domain that they totally forgot to check to see what I was doing there. My only insect pest problem was an infestation of aphids on my late season radishes.
This year, the bugs have apparently recovered from the initial shock. Everything was going along nicely until I noticed small holes like a miniature shotgun blast in the leaves of my tomatoes. At first, I did not see any culprits. However, I kept checking and after a couple of days, I saw tiny black beetles. These critters were about 1/16" - 1/8" long, and appeared to be entirely black to my not-so-wonderful old eyes.
That night, I hit the Internet. After a few minutes on Google, I was pretty sure I was dealing with flea beetles. After about half an hour, I found a site with a photograph of the little blighters. My flea beetle sighting was confirmed.
Now it was clear from my reading that these beetles were not an immediate threat. While they can kill a seedling, my plants are 2-3 feet tall by now and more than capable of growing enough new leaves to replace any damage. However, just two feet away, my late-season transplants were only a few inches tall, protected for the moment by half-gallon plastic bottles with the bottoms cut out. By the weekend, they will outgrow these mini-greenhouses. I also reseed other pots in the planters periodically. Much as I hate killing things, these bugs would have to go.
Now my problems begin.
These guys are small, they are fast and they jump. I also have about 30 well developed plants in my planters. Hand picking was clearly not an option.
As an organic gardener, I am severely limited in what I can use as a pesticide. Most articles recommended using enough Malathion to wipe out a third-world village. I can't use it, and I wouldn't even if I could. I had to find an alternative approach. While I can use certain pesticides like ones based on Pyrethrum, I prefer to avoid them if I can. Then, I found an article about getting rid of flea beetles by dusting with Diatomaceous Earth. This was perfect, since Diatomaceous Earth is not a pesticide in the usual sense. Best of all, I remembered that we had some in the shed.
Diatomaceous Earth is not a normal pesticide since it does not poison insects. It is like very-fine sand, made of the broken up shells of tiny little things called diatomes. Its effect is purely mechanical, rather like sprinkling finely-ground broken glass on your plants. It tends to stick to insects because of tiny electrical charges, like dust sticks to your TV screen. It will cut up any insect that touches it. It is also a drying agent so it will dehydrate them on prolonged contact. Since it is not a poison, insects cannot become immune to it. They have two choices, leave within 48 hours, or die.
In the shed I found a big 5-pound can of Concern Diatomaceous Earth. My wife had bought it and used it back when she was gardening about 20 years ago to keep slugs off her kale. Since then the open can has sat on a shelf in my non-too-waterproof shed. This was most likely a block of cement by now. The top had a twisty plastic disk. In one position it was closed, in another, it was open, and in a third, it had holes like a red-pepper canister for pizza. I tried the holes and gave it a shake over my garden trash. Out came a sprinkling of white flour-like powder. We were in business.
I made sure all the plants were properly watered, and then gave their leaves a shot with the mist setting on my garden hose, just so they had a fine mist over them. This stuff is basically safe, but it will irritate your eyes and you do not want to breathe it, so I put on safety glasses and a paper dust mask. Stand well back from the plants as you apply it, and don't forget to give your hands a good wash right after you use it, to prevent accidental contact with eyes, nose and/or mouth. I twisted the can top until 2-3 holes were open. I carefully shook the can over each plant until I had a fine sprinkle over every leaf and the earth at the bottom of the pot. The mist helped the powder stick to the leaves. We have not had any rain since I applied the dust, and I bottom water usually, so my plants still look pretty spooky, like ghost tomatoes, but I have not seen any flea beetles recently.
Diatomaceous Earth will kill just about any bug that crawls. Slugs and snails hate it too. It is no real use against flying pests. Also, it is not too effective against aphids since they hide under the leaves. You can buy a hand pump or use a puff bottle to get the dust up under leaves, and you can mix the powder with a dilute solution of any potassium based soap, and spray under leaves. Both methods allow it to be used against aphids. However, since simple soap solution is often enough to discourage aphids, it may not be worth the effort.
As well as having all kinds of uses in the garden, the packet recommends using it inside the house too, in corners, behind the refrigerator, and under the sink. Anywhere you want to stop bugs -- roaches, ants, earwigs, whatever. The big thing about Diatomaceous Earth is that is pretty safe for birds and mammals. You can sprinkle it around and in pets bedding to control fleas and ticks. I have even seen articles saying that you can rub it into your cat or dogs fur, but I am not sure I would want to try that myself without checking with my vet first.
Diatomaceous Earth is environmentally safe too, I mean, it's just sand -- silica dioxide. Plants can't absorb it. It does not get into the food chain. It does not poison birds or mammals that eat the dead or dying bugs. It is just an inert substance. No biggie. It is non-staining but you don't want to accidentally get it in other places, so if you get it on your clothes, wash them.
Now when you think about it, almost all the alternative ways to kill bugs use chemical neurotoxins that are extremely poisonous, even in very small amounts. Trace amounts of these toxins can do nervous system damage and potentially cause birth defects. Obviously, Diatomaceous Earth is quite an improvement since it is non-toxic. If you have ever eaten anything made of flour, you have already eaten some Diatomaceous Earth. However, that does not mean you should sprinkle it on your cornflakes. It is not entirely benign. You do NOT want to breathe the fine dust, and it irritates the eyes. If a child were to eat any, don't panic, but do give the local poison center a call. If you get any in your eye, flush it with water for about 15 minutes. If irritation persists, call a doctor.
Diatomaceous Earth has two down sides. First, it washes off with heavy rain. While this is good since it makes it easy to clean up, it does mean that you will have to reapply it if fighting a stubborn infestation. The second problem is that it kills almost anything. While that does make it useful in a wide range of circumstances, you are killing the good bugs with the bad. You may accidentally kill ladybugs that will happily hunt down aphids for you, while allowing the aphids to hide under leaves. Worse, you may kill bees which you need for pollination. Luckily, it is early in the tomato season. Consequently, I did not have to worry about bees at this time. If my tomatoes were bearing flowers, I would have tried to keep the powder on the lower branches away from the flowers.
(I know. In NJ, tomatoes would normally have flowers this late in June. I habitually cut off the first few flowers on tomatoes, to give the plant a chance to fully develop before it tries to bear fruit. This delays the first fruit production but greatly increases the yield.)
This is a crawling insect control containing Silicon dioxide, from diatomaceous earth 85.0% and 10.0% other elemental oxides, with 5.0% inert ingredients. Pesticides should only be used as a last resort. However, as a relatively-benign eco-friendly pesticide with a wide range of uses, I have to recommend this product. For sitting on the shelf for twenty years in its original container and still being useable, I must give it five stars.
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Building Greenhouses and Planters:
- Chapter 1 - Pallets
- Chapter 2 - Planters
- Chapter 3 - Greenhouses
- Chapter 4 - Equipment
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Yes, I know the government tells us that Malathion is safe. That is the same government that claimed there were WMDs in Iraq and that the air at Ground Zero in NYC was safe to breathe, and that FEMA was going to help New Orleans. There's a trend here...
I have degrees Chemical Physics and Chemistry. Back in the early 1970s, I did post-graduate research and wrote my thesis on the health effects of pesticides, mostly DDT and Malathion. Even then, it was pretty clear that Malathion was NOT safe. However, this is outside the bounds of the current review. Look here -- http://www.chem-tox.com/malathion/research/ -- if you would like to learn more.
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