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okiedawn1

Organic Pesticides

Okiedawn OK Zone 7
16 years ago

There have been a lot of pest questions lately on this forum, and it is that time of year, so here's a general synopsis of the basic pesicides.

There are many organic products available, but these are the most commonly available pesticides. If you choose to use any of these, please follow the directions very carefully. Some of them are so toxic that I won't use them although many organic gardeners do.

Bt: Bt is Bacillus thuringiensis, a form of bacteria, commonly used as an organic pesticide. There are many strains of Bt available. One strain is used as a caterpillar killer, another as a potato bug killer and another can be found in mosquito larvaecides. Bt works as a poison, affecting the targeted insect's stomach where it releases toxins that cause the insect to stop eating and starve to death over a period of a few days. Although the pests take a few days to die, they generally stop feeding shortly after ingesting the Bt.

Bt tends to be pest-specific and only affects the targeted, or susceptible, insect. Unfortunately, in the case of the strain of Bt used as a caterpillar killer, it will affect all caterpillars and moths, so must be used carefully or you will wipe out the butterfly/moth population. This is generally safe for use in the veggie garden or on fruit trees up to the day of harvest.

Horticultural Oil: This is a very highly refined petroleum oil which is availably commercially. When I was younger it was generally referred to as dormant oil because you mostly used it during the dormant season. New production methods have given us a superfine oil that also can be used when plants are not dormant. Be cautious, though, because in our climate it can still burn foliage in full sun/hot weather. Follow dilution and application directions very carefully.

This product works by coating insects with the oil, which suffocates them and/or also disrupts their ability to feed.

It is most effective on soft bodied insects. It has a very low toxicity to humans, pets, and birds.

Whereas you can use regular dormant oil in the dormant season, use only superfine or summerweight oil at any other time. The heavier dormant oil can easily kill plants that are sprayed when NOT dormant.

Insecticial Soap: This is basically a sodium and/or potassium soap in combination with fatty acids. You can buy a commercial product or mix up your own. This product works by penetrating the targeted pest's exoskeleton and caused its cells to collapse leading to death of the targeted pest. It is only effective when sprayed DIRECTLY on the targeted pest. It is a very safe product for humans to apply but is only effective on pests with which it makes contact before it dries.

I am always very cautious about using soap of any kind because it can burn foliage in our heat and climate and some plants are very sensitive to it and will die if sprayed with it. It can even cause severe stress to plants that don't show alot of foliar burn. Use carefully. This is generally safe for use in the veggie garden or on fruit trees up to the day of harvest.

Neem: This is a botanically derived substance with two different compounds from the fruit of the neem tree: azadriachtin and liminoids. This is a commercially available product and you need to follow label directions carefully.

It is an indiscrimate pesticide, so it will kill almost every insect pest with which it makes contact. However, it works by disrupting the insect's hormonal system which prevents the insect from developing and maturing. Thus, it is most effective on immature insects and on all species that undergo a full metamorphosis. It is less effective on mature insects.

Neem is generally considered non-toxic to humans, but can be harmful to pets so keep them off treated areas until those areas are dry. It can be slow acting and is not considered a quick fix. Sunlight breaks it down pretty quickly too.

I will seldom use neem due to its indiscriminate nature and the fact that I have a lot of pets and desirable wildlife.

Pyrethrins: This is an organic product derived from a member of the Chrysanthemum family. You can purchase it commercially in a powdered form that you dust onto plant foliage. It works as a stomach poison in the targeted insect causing a fairly rapid death, which is good. It is very, very toxic to bees, which is BAD. Because it is NOT non-toxic to all living creatures, it should be used as a last resort for very heard-to-kill insects. If you must use it, apply it when bees and beneficial insects are not active.

A lot of pyrethrin products have an additive called PBO which stands for piperonyl butoxide. It is a synergist that increases this product's killing power. PBO has been found to be toxic to mammal's livers, so use very carefully or only purchase pyrethrin products that do not have PBO as an additive.

Though used by many organic gardeners, this one is too toxic for me.

Rotenone: This is a product which is derived from the roots of tropical legumes. Although once recommended by many 'experts' in the organic gardening world, this product has largely fallen from favor because some scientific studies have linked some rotenone products to the possible development of Parkinson's Disease since the early 1980s.

It is a dust you scatter on the plant. If you choose to use it, take extreme care to avoid inhaling it. It works by inhibiting normal cellular processes and causing tissue death in cells due to a lack of oxygen. It is a very broad-spectrum pesticide, so be sure to apply when bees and beneficial insects are not active.

I obviously don't use this one either.

Sabadilla: This is the ground-up seeds of the sabadilla lily and it is highly toxic to bees, so use it only as an absolute last resort. It is commercially available as a dust, although you can also mix it up with water and apply as a spray. It is a stomach poison that is particularly effective on true members of the bug family. (That is members of the Hemiptera order.) It has been found to be an irritant to mammals' mucous membranes.

I would never, ever use this one, but some organic gardeners do.

Spinosad: This is a relatively new product on the organic market, having been around 3 or 4 years now. It is a naturally occurring product derived from the fermentation of a bacteria known as Saccharopolyspora spinosa. The good news is that it is a highly effective borad spectrum pesticide that controls many agricultural pests. It has SO FAR been shown to have little to no toxicity to non-targeted organisms. You will find it in many products, including as the active ingredient in a fire ant bait and a mosquito control product.

The downside is that it is very new, and often you don't seem toxicity problems crop up until a product has been in use for quite a while. I have used it and have been very happy with its effectiveness.

Nicotine products: I haven't seen nicotine spray or dust products in a long time, but they might still be out there. I know that many 'recipes' for nicotine-derived products are still everywhere on the internet.

Personally, I wouldn't use any of these nicotine products or recipes. The one I remember my granddad's generation using was called Black Death and it was highly toxic to many living creatures. Also, ANY tobacco product should never be used near tomato plants or any of their relatives. Enough said.

Hope this is helpful to everyone struggling with pests this year. Keep in mind there are other products that are useful as repellents, but not as pesticides.

Dawn

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