- Author: Scott Oneto
By Scott Oneto, Farm Advisor, University of California Cooperative Extension
Soaps have been used to control insects and combat pests for hundreds of years, but their effectiveness as pesticides has been scientifically established only recently. 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. Researchers have been studying how soaps work in combating pests. Some soaps simply wash off the outer waxy coating of the insect's cuticle, destroying its watertight quality and causing the insect to dry up and die. Other soaps have additional insecticidal properties that may affect the nervous system. These soaps appear to have toxic effect only against plant-eating insects and thus may spare beneficial insects such as ladybird beetles (ladybugs), lacewings, and predatory mites. In addition, high pressure sprays may wash some insects off the plant and other insects may be immobilized in soapy water, making them easier to rinse off the plants.
Soaps will kill many insect pests, including aphids, mealybugs, whiteflies, spittlebugs, rose slugs, and soft scale on most houseplants, ornamentals, and fruit trees. But because soaps have little or no residual action, sprays should be applied at regular intervals until the population is controlled or eliminated.
Soaps 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 available over-the-counter for control of insects and mites. Available under a variety of trade names, the active ingredient of all is potassium salt of fatty acids. Insecticidal soaps are chemically similar to many household liquid hand soaps. However, there are many features of commercial insecticidal soap products that distinguish them from the dish washing liquids or liquid hand soaps that are sometimes substituted.
Insecticidal soaps sold for control of insects:
- are selected to control insects
- are selected to minimize potential plant injury
- are of consistent manufacture
Some household soap also makes 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 around2 to 3 percent. (Table 1)
One of the most serious potential drawbacks to the use of Household 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. Certain tomato varieties are also 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 with in 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.
- Author: Missy Gable
Annual reappointment is a requirement for all volunteers working with UC Division of Agriculture and Natural Resources. Please read this update thoroughly and direct any questions regarding the appointment process to your county's Program Coordinator, Advisor or County Director.
Reappointment began June 1 and must be completed by all Active, Limited Active, First-Year, Gold Badge and Platinum Badge volunteers. If you haven't finished the process already, it can be done in three easy steps!
Step One: Select “Complete Agreement Now” in VMS
- Log into VMS, vms.ucanr.edu
- Select “Complete Agreement Now” from prompt box at top of VMS home screen
Step Two: Complete all three sections to fulfill county requirements for participation
Step Three: Verify Date Completed Displays and Print a Copy for your Records
- Author: Karey Windbiel-Rojas
Find out more about California Invasive Species Action week, species of concern, schedule of events, and what you can do to help prevent invasive species at https://www.wildlife.ca.gov/Conservation/Invasives/Action-Week.
The University of California has information about exotic and invasive pests on the UC IPM Exotic and Invasive Pests page and the Center for Invasive Species Research.
Also, read some of our recnt blog articles on invasive pests and their impacts in urban areas:
- Help Protect California's Citrus from Asian Citrus Psyllid
- Invasive Pests of Concern for California's Urban Farmers
- Bagrada Bug Continues to Spread in California
- Don't Grow Crazy: An Update on California's PlantRight Program
- Brown Marmorated Stink Bug
- Exotic Pests Invade California Landscapes
Once established, invasive species are extremely difficult to eradicate and can cause not only ecological disruption, but economic problems as well. Everyone has a part to play to keep exotic and invasive species from coming into California and spreading throughout the state.
- Author: Paula Olson
Astrid, Pirate, Highway and Toasty are just four of the 120 sea lions and elephant seals currently under care at the Pacific
The majority of PMMC's patients are pups found stranded on our beaches. According to the National Oceanic and Atmosphere Administration (NOAA), pups are going hungry because unusually warm water along the Pacific coast has made it more difficult for their mothers to find food.
Climate change, drought and pollution are affecting each and every earthly being and so, it is with great commitment, that several UCCE Master Gardeners of Orange County have taken on the task of revitalizing the garden area in and around PMMC.
As supporters visit the Center to learn more about the plight of the marine mammals, they can also learn about native plants, water-wise gardening, beneficial insects and water quality, bringing their experience full circle.
Founded in 1972, the PMMC is nestled at the foot of the Laguna Canyon hills juxtaposed to a waterway that flows directly into the ocean. Mixed in with the sound of barking sea lions, frogs croak. Along the fence leading down to the creek and near brick walkways Master Gardeners have planted more than 50 new plants including Butterfly Cassia, California Fuchsia and White Yarrow, attracting pollinators and using little water.
“It is the perfect place to create a learning environment for the general public,” said Master Gardener and project lead, Ingrid Cebula. “The garden adds value to the entire experience of what each of us can do to help support our precious earth.” Garden plans also include informational signs throughout the landscape and free educational materials at the PMMC gift shop. Master Gardeners can be frequently seen tending to the garden, ready to answer questions.
Pacific Marine Mammal Center's mission is to rescue, rehabilitate and release marine mammals and to inspire ocean stewardship through research, education and collaboration.
For more information visit www.pacificmmc.org or contact Ingrid Cebula at idcebula@gmail.com
- Author: Lauren Snowden
The Statewide UC Master Gardener Program in partnership with the California Department of Water Resources has secured funding to provide regional drought workshops. The workshops will focus on the critical issue of water management in the home landscape and provide a forum for discussion of drought-related UC Master Gardener outreach around the state. The statewide office will be looking for interested host counties to work in partnership to roll out these workshops to the UC
To provide continuing education for UC Master Gardeners, the Statewide UC Master Gardener Program provides regional workshops and trainings. These events are always popular and serve as a place for Master Gardeners to learn new things, refine their skills, interact with University of California scientists, and meet other gardeners. By promoting activities where UC Master Gardeners learn together, the Statewide UC Master Gardener Program ensures that Master Gardeners are up-to-date with the most recent research recommendations from the University of California.
Together, through this series of workshops, the UC Master Gardeners are making a difference! Hope to see you at one of “The New California Landscape” drought workshops!
Tags: Statewide UC Master Gardener Program; Training; Workshop; Drought