Insect Control: Soaps and Detergents by W.S. Cranshaw 1 Quick Facts... Soaps can be used to control a wide range of plant pests. Small, soft-bodied arthropods such as aphids, mealybugs, psyllids and spider mites are most susceptible to soaps. The ease of use, safety and selective action of soaps appeal to many people. Limitations of soaps include the need to wet the insect during application, absence of any residual effectiveness, and potential to damage some plants. Soaps or detergents used for control of insects are applied as dilute sprays, mixed with water to produce a concentration of about 2 percent. Soaps have been used to control insects for more than 200 years. Recently, there has been increased interest in and use of these products. This change is due to a better understanding of how to use soaps most effectively and a desire to try insecticides that are easier and safer to use than many currently available alternatives. How soaps and detergents kill insects is still poorly understood. In most cases, control results from disruption of the cell membranes of the insect. Soaps and detergents may also remove the protective waxes that cover the insect, causing death through excess loss of water. Soap-Detergent Sprays Soaps and detergents act strictly as contact insecticides, with no residual effect. To be effective, sprays must be applied directly to and thoroughly cover the insect. Several insecticidal soaps are distributed for control of insects and mites. Available under a variety of trade names, the active ingredient of all is potassium salt of fatty acids. Soaps are chemically similar to liquid hand soaps. However, there are many features of commercial insecticidal soap products that distinguish them from the dishwashing liquids or soaps that are sometimes substituted. Insecticidal soaps sold for control of insects: are selected to control insects; are selected to minimize potential plant injury; and are of consistent manufacture. Some household soaps and detergents also make effective insecticides. In particular, certain brands of hand soaps and liquid dishwashing detergents can be effective for this purpose. They are also substantially less expensive. However, there is increased risk of plant injury with these products. They are not designed for use on plants. Dry dish soaps and all clothes-washing detergents are too harsh to be used on plants. Also, many soaps and detergents are poor insecticides. Identifying safe and effective soap-detergent combinations for insect control requires experimentation. Regardless of what product is used, soap-detergent sprays are always applied diluted with water, typically at a concentration of around 2 to 3 percent (Table 1). Susceptible Insects Most research with insecticidal soaps and detergents has involved control of plant pests. In general, these sprays are effective against most small, soft-bodied arthropods, such as aphids, young scales, whiteflies, psyllids, mealybugs, and spider mites. Larger insects, such as caterpillars, sawflies and beetle larvae, generally are immune to soap sprays. However, a few large insects, including boxelder bugs and Japanese beetles, are susceptible. Insecticidal soaps are considered selective insecticides because of their minimal adverse effects on other organisms. Lady beetles, green lacewings, pollinating bees and most other beneficial insects are not very susceptible to soap sprays. Predatory mites, often important in control of spider mites, are an exception: a beneficial group of organisms easily killed by soaps. Application One of the most serious potential drawbacks to the use of soap-detergent sprays is their potential to cause plant injury -- their phytotoxicity. Certain plants are sensitive to these sprays and may be seriously injured. For example, most commercial insecticidal soaps list plants such as hawthorn, sweet pea, cherries and plum as being sensitive to soaps. Portulaca and certain tomato varieties also are sometimes damaged by insecticidal soaps. The risk of plant damage is greater with homemade preparations of household soaps or detergents. When in doubt, test soap-detergent sprays for phytotoxicity problems on a small area a day or two before an extensive area is treated. Plant injury can be reduced by using sprays that are diluted more than the 2 to 3 percent suggested on label instructions. To reduce leaf injury, wash plants within a couple of hours after the application. Limiting the number of soap applications can also be important, as leaf damage can accumulate with repeated exposure. However, because of the short residual action, repeat applications may be needed at relatively short intervals (four to seven days) to control certain pests, such as spider mites and scale crawlers. Also, application must be thorough and completely wet the pest. This usually means spraying undersides of leaves and other protected sites. Insects that cannot be completely wetted, such as aphids within curled leaves, will not be controlled. Environmental factors also can affect use of soaps. In particular, soaps (but not synthetic detergents) are affected by the presence of minerals found in hard water, which results in chemical changes producing insoluble soaps (soap scum). Control decreases if hard-water sources are used. Insecticidal soaps may also be more effective if drying is not overly rapid, such as early or late in the day. Soaps and detergents can offer a relatively safe and easy means to control many insect pests. As with all pesticides, however, there are limitations and hazards associated with their use. Understand these limitations, and carefully follow all label instructions. Table 1: Approximate mix to produce various dilute soap sprays. Percent dilution desired Approximate amount of soap to add to water to produce: Gallon Quart Pint 1 2 1/2 Tbsp (-) 2 tsp (+) 1 tsp (+) 2 5 Tbsp (-) 4 tsp (+) 2 tsp (+) 3 8 Tbsp (+) 2 Tbsp (+) 1 Tbsp (+) 4 10 Tbsp (-) 2 1/2 Tbsp (+) 4 tsp (+) (+) Will produce a solution of slightly higher concentration than indicated. (-) Will produce a solution of slightly lower concentration than indicated. 1Colorado State University Extension entomologist and professor, bioagricultural sciences and pest management. 12/96. Reviewed 3/08. Colorado State University, U.S. Department of Agriculture and Colorado counties cooperating. CSU Extension programs are available to all without discrimination. No endorsement of products mentioned is intended nor is criticism implied of products not mentioned. Go to top of this page. Updated Friday, August 03, 2012

Thanks to all who responded, I thought it was possibly the metal in the containers, but it's most likely the soap from what "Sweeby" says. I'll give the Dial clear liquid a try, it's less expensive than replacing all the containers throughout the house.

Hazel, Hmmm, I have rarely seen aphid molt. I guess the ladybugs eat them before they live long enough to molt. Honestly, we have almost too many ladybugs--they try to come into the house to overwinter. I let them stay in the mudroom but they cannot come any further into the house or I vacuum them up and dump them back outdoors, so instead they overinter in the insulated barn-style garage and in the greenhouse, which is great since I have some plants overwintering in the greenhouse every year. I feel like once you get a good ladybug population established (and it has begun...because you have ladybugs in the garden), the aphids are a very brief problem and then the ladybugs gobble them up and that is that. If the damage to the foliage is not too extensive, the tomato plants will put out new foliage within the next couple of weeks and should survive. If the the damage is too severe, they won't. It really is a case of just waiting and watching and seeing what happens. I'm sorry the homemade soap spray damaged your tomato plants. I see that all the time here in southern OK, even as early as March if we are having high temperatures in the 90s, which happens occasionally (we even hit the 90s on a day or two in February this year). Our sunlight and heat are just too intense for homemade soap sprays to be successfully used without a high risk of damage, especially on tomato foliage which is very tender and easily damaged by many things. If I have to use insecticidal soap at all, I use a commercially prepared one. They are made in a way that their droplets of soap are smaller and less likely to damage anything. Still, because soaps can cause damage, I rarely use a soap spray when we are hitting highs any higher than 80 degrees, and I rarely use one in the sunshine. If I have to use soap sprays, I use them in the evening after the garden is shaded by adjacent trees, and I don't use them often. I can, in fact, go years without using a soap spray. Really, with most insects, if I cannot handpick and drown them, snip them in half with scissors, or kill them with an organic bait (like SlugGo Plus for snails, slugs, pillbugs, sowbugs and cutworms or Semaspore for grasshopper nymphs), I just leave them alone and let them be about 99.9% of the time. If I am patient, the beneficial insects, toads, frogs, birds, lizards, turtles, etc. will eat a majority of the pest insects for me. Some things, like stink bugs and leaf-footed bugs are hard to catch and kill and I don't like to spray broad-spectrum insecticides (not even organic ones), so I just do the best I can with those. Sometimes I can snip a stink bug or leaf-footed bug in half with my garden scissors, but a lot of the time they get away from me. With the similar squash bugs, I keep a lint roller in my garden tool bucket and roll it over them, picking them up with it. Then I quickly peel that part of the lint roller paper off the roller and wrap it around them, firmly entrapping them, and I put them in a trash can with a lid so they cannot escape if they somehow manage to get free of the lint roller paper. Rainy years are always more challenging. I haven't used Miracle Grow on any plants yet, but I wouldn't hesitate to use it if the constant rainfall starts keeping the plants from taking up nutrients with their roots. Sometimes a good foliar feeding will help struggling plants, whether you use MG, Liquid Kelp, Fish Emulsion, Compost Tea, Garrett Juice (more as a plant tonic than a fertilizer) or whatever. Once your soil is more well-established and has the right level of biological activity in the soil, your organic fertilizers will be adequate to support great plant health, growth and productivity most years. There's a terrific book by Jeff Gilman about what truly works in organic gardening. It is called "The Truth About Organic Gardning: Benefits, Drawbacks and The Bottom Line". I really like this book. It was published in 2008 but I didn't read it until a couple of years ago. I had gardened 99.9% organically since 1999 (and even before that I didn't use synthetic pesticides more than maybe once a year and didn't like them either) so felt I understood organic gardening pretty well already, but really enjoyed the book anyway as it helped me understand some of the science behind some common organic practices. I like his scientific approach to studying organic practices to see what actually does work and what doesn't work and I like his explanations about why some things work and others don't seem to. Before I got the book, I was concerned that maybe he was sort of anti-organic, as many other university horticulture professors seem to be, but he isn't. His explanations on every topic in the book just blow me away in their thoroughness and in the way he looks at all sides of an issue. I really love this book, and have been meaning to get his other book and read it too. One section early in this book really gave me a lot of food for thought. It was subtitled "How organic is organic enough?" and made me rethink some long-held beliefs. From the first day we broke ground here (and, lol, we broke ground for our first garden here a year before the builder broke ground to build the house), my primary focus always has been on building healthy soil. If you focus on building healthy soil that is rich in organic matter, all your other garden problems become minor issues. However, building healthy soil takes time, especially if you are doing it in drought years when there is very little moisture. It took me a good ten years to get our soil to the point that I really was happy with its improvement, and at least half those years were horrendous drought years when nothing I did seemed to keep the garden as happy and as productive as I wanted it to be. (Rain does make a huge difference, as does the absense of rain.) Conversely, without healthy soil teeming with microbes, it is hard to have a healthy organic garden. I have focused so long on feeding the soil and letting the soil feed the plants that it is hard for me to suggest to someone that maybe there are times when a synthetic fertilizer would be beneficial, but there are times when it is....and your situation is likely to be one of them. I used Miracle Grow liquid fertilizer without hesitation in our early years here when the soil wasn't yet in good shape and didn't feel bad about it. I still use the Miracle Grow Moisture Control soil-less mix for growing on seedlings (after starting them in a sterile, soil-less mix) and I use it in all my containers at times, though I still add all the rotted wood and leaf mold and compost that I can to the containers as well. (Growing in containers is an entirely different process from growing in the ground, so you have to adapt your practices accordingly,and I learned that slowly and the hard way over many years of growing in containers.) In 2007 we had so much rain that my plant roots stayed waterlogged, and it was foliar feeding with Miracle Grow that saved the tomato and pepper plants and gave us a harvest that summer. Otherwise, I think we would have gotten almost nothing from the constantly-waterlogged garden. At that point, our soil was not in the fine condition that the soil in the raised beds now is in. Last year, we had more than twice as much rain as we had in 2007 (78" versus 2007's 37" or 38"), and the soil is so much better now that I didn't have the same issues with plant roots being too clogged with water to function properly and I didn't have to foliar feed with anything. It is amazing what a difference a few more years of soil improvement has made. Oh, and I should clarify---it wasn't that the rainfall was so heavy overall in 2007 as our rainfall barely was average for the year overall, it is just that so much of it fell in late spring and early summer all at once that the heavy moisture overwhelmed the plant roots). If I learned anything at all from last year's flooding and constant moisture, it was that we finally, maybe, had the soil I'd been working so hard to achieve, in all ut the newest raised beds (and they still have a long way to go). Every year has its own challenges. In a drought year, as long as I water with soaker hoses or drip irrigation lines, I never have to use a fungicide at all---not a synthetic one and not an organic one. The challenge in that sort of year isn't foliar disease like it is in a very wet year, it is simply the lack of moisture, the often insane heat, and the traveling hordes of grasshoppers that fly in from adjacent fields and can strip a garden bare in just a day or two. You just deal with whatever happens in any given year, learn from that year, and use what you learned the next time we have a year with similar weather. One of the challenges of growing here is that one year we'll have hot weather and almost no rain and the next year it will be much milder and wetter and we almost forget what heat and drought can do to a garden. It seems we rarely have the same weather two years in a row, so often we're scrambling to deal with whatever Mother Nature throws at us. It keeps us on our toes. Dawn

If it's a Sukkot thing, how about this persimmon and pomegranate salad? It's a very cheerful dish because of the colors and pomegranate is very much the Sukkot fruit: 1/2 cup pecan halves 3/4 cup orange juice, divided 2 teaspoons cornstarch 1 1/2 tablespoons honey 1/4 cup extra-virgin olive oil 1/2 lime, juiced 7 fresh tarragon leaves, thinly sliced crosswise, or more to taste salt and ground black pepper to taste 1 (8 ounce) package herb salad mix 2 Fuyu persimmons, peeled and each cut into 8 pieces 1 large pomegranate, peeled and seeds separated Directions Preheat oven to 375 degrees F (190 degrees C). Spread pecans onto a baking sheet. Bake pecans in the preheated oven until toasted and fragrant, 5 to 7 minutes. Set aside to cool. Whisk 1/2 cup orange juice and cornstarch together in a small saucepan; cook and stir over medium heat until mixture thickens, 3 to 5 minutes. Remove saucepan from heat and stir in honey until dissolved. Stir remaining 1/4 cup orange juice, olive oil, lime juice, tarragon leaves, salt, and pepper into orange juice mixture. Chill dressing in refrigerator, at least 30 minutes. Spread herb salad mix into a serving bowl or on individual plates; top with persimmon slices, pomegranate seeds, and pecans. Drizzle cooled dressing over salad. http://allrecipes.com/recipe/235229/persimmon-and-pomegranate-salad/?internalSource=rotd&referringId=1111&referringContentType=recipe%20hub&clickId=cardslot%201