How Can I Control Pests Organically?

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Because they break down quickly, natural insecticides are less likely to impact honeybees and other beneficial insects.

Because they break down quickly, natural insecticides are less likely to impact honeybees and other beneficial insects.

Natural insect control products are derived from plants, microorganisms and other naturally occurring materials. These products can successfully control many insect pests in gardens and landscapes when applied properly. You may find simply substituting natural products for synthetic insecticides does not provide the same results.

What’s Different about Natural Insecticides?

One of the most important differences between natural and synthetic insecticides is how long they last once they are applied. Natural insecticides kill pests that are present at the time of application, but then break down quickly, often within a few days. These products don’t stick around long, reducing the chance that pets, people, wildlife, and beneficial insects will accidentally be exposed to them. Unfortunately, this also reduces their ability to provide long term pest control. As a result, natural insect control products must be applied more frequently than synthetic products to control ongoing or recurring pest problems.

In addition, most natural insecticides are not absorbed by plants. They kill insect pests by direct contact during application or shortly thereafter, or when pests eat treated leaves. Because of this, complete coverage of pest infested plants is essential for good results. Since they remain active for a relatively short time, natural products should only be applied when pests are present, not as a preventative.

Like all pesticides, natural products work best when populations are low, so check garden and landscape plants frequently for problems and treat as soon as pest insects are found. Before treating, make sure to have the pest correctly identied and confirm it is a problem for which treatment is necessary. Many insect outbreaks are temporary, causing no serious injury, and therefore do not require control.

Which Products Control Which Pests?

Colorado potato beetle larvae

Colorado potato beetle larvae can be controlled with spinosad, a natural insecticide.

Most insecticides can only control certain pests. Before you apply a pest control product make sure the pest is correctly identified and you have chosen a product known to control that pest. Common insect pests that can realistically be controlled with natural products include aphids, caterpillars, scale, mealy bug, whitefly, and spider mites.

Horticultural oils and insecticidal soaps are available from most garden centers. Both can be used to control aphids, mealy bug, mites, thrips, lace bug, and whitefly. In addition, horticultural oil will control scale insects that are common on many trees and shrubs. Both of these products kill insects by direct contact only. To be effective, sprays must be applied directly to and thoroughly cover the insect pest. Since there is no residual activity, follow up applications are often needed. Some plants are sensitive to these products so be sure to check label directions before spraying and avoid applying in extreme heat.

Neem Oil and azadirachtin are closely related products that will control aphids, mealybugs, mites, thrips, and whitefly. Neem oil is derived from the seed of the neem tree, which is native to southeast Asia. Azadirachtin is one of the more than 70 compounds produced by the neem tree and is thought to have the highest level of insecticidal activity. Products containing either active ingredient are available at many garden centers. Both are quickly broken down by sunlight and work best when applied to immature insects.

If caterpillars or Colorado potato beetles are your problem, pick up a product containing spinosad. This byproduct of the fermentation of a rare type of filamentous bacteria kills primarily through ingestion but also on contact. Spinosad is quickly broken down by sunlight but is also partially taken up by leaf tissue, providing a slightly longer period of control than many natural insecticides.

Other readily available natural insecticides include B.t. and pyrethins. Officially known as Bacillus thuringiensis var. kurstaki, B.t. is a naturally occurring soil bacteria that effectively controls young caterpillars. Because it breaks down rapidly in sunlight, B.t. is best applied in the evening or on cloudy days. Pyrethrins are derived from the flowers of certain species of Chrysanthemum. They control a wide range of insect pests, but are harsher on beneficial insects than most natural products.

Reduce the need to control pests by using best management practices to keep pest populations in balance. These practices include improving your soil by tilling in compost, mulching, choosing plants adapted to the site conditions, applying water and nutrients when needed to prevent plant stress, and encouraging beneficial insects by planting a diversity of plants and flowers.

Learn More!

Learn more about natural pest control from these past Pender Gardener articles:

Learn more about natural pest control products from the Resource Guide for Organic Insect and Disease Management, available online from Cornell University: http://web.pppmb.cals.cornell.edu/resourceguide/

Use Extension Search to find research based information from Cooperative Extension systems across the U.S.

Visit your local Cooperative Extension office to learn more about gardening and landscape care. Go to https://www.ces.ncsu.edu/local-county-center/ to find your county Extension center or post your questions to be answered online via Extension’s ‘Ask an Expert’ widget.

Contact your local Cooperative Extension office to get expert advice from an Extension Master Gardener Volunteer:

Written By

Photo of Charlotte GlenCharlotte GlenState Coordinator, NC Extension Master Gardener Program (919) 515-1226 charlotte_glen@ncsu.eduHorticultural Science - NC State University
Updated on Nov 19, 2015
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